Solar Academy
Welcome to Solar Academy. It's time to gain some insight into this advancing technology. Adding a solar photovoltaic system to your home or business is a significant investment. It can pay for itself and reap future benefits, provided one makes informed, educated decisions. Solar Academy will try to help you make those informed decisions through facts and opinions based on our more than fifty years of collective solar knowledge along with thousands of active installations and hundreds of troubleshooting service calls. Through these experiences, we are constantly revaluating materials, processes and technologies to improve and provide best-in-class service to our customers… current and future.
So go grab a cup of your favorite brew, sit back and learn.
Sizing a Solar PV System
The first question a homeowner will ask is, "What size solar PV system should I get?" Truthfully, the answer to that question is complicated, because everyone's needs are different. There is no one-size-fits-all solar PV system. For example, say you live with your spouse in a comfortable 1,800 square-foot three bedroom home, with an SUV and pickup in the garage. Your energy needs are likely conservative. Across the street, in the exact same model as your home, there's a younger couple with three rambunctious pre-teens; running in and out with kids from the neighborhood, leaving lights on and doors open, playing with their various electronic gadgets long into the night, baths, showers, meal prep and clothes washing/drying for a family of five, etc. And at least one EV or Hybrid in the garage. That family's energy needs will be more than double.
A solar installer will ask you for a recent utility bill to try and determine your average annual energy usage. That assumes you've lived in your home for a year or longer. Energy usage will fluctuate up and down over a twelve-month period, as will solar production. Finding the right balance is key. Any homeowner in Florida who installs solar PV will need to sign an Interconnection Agreement with their utility provider. The agreement provides restrictions for the type and size of system that can be installed, along with safety requirements to protect linemen from injury and the grid - the massive regional interconnected system that ensures everyone has electric power 24/7/365. In years past, utility companies paid homeowners for any excess solar power sent back to the grid, sometimes penny-for-penny, through a reverse-utility meter (a meter designed to monitor energy in both directions). Some even offered rebates for installing solar on your home. Though, once utility companies realized with all the new homeowner-owned solar coming online, they were losing money every month, everything changed. Today, with a new Interconnection Agreement, utility companies will pay you nearly nothing for excess energy sent back to the grid. It's no longer in your best interest to install a solar PV system that exceeds your needs. Your utility company is still big on solar, provided they own it and can charge you to use it. It's just business.
In Florida, utility rates don't vary depending on time-of-day as they do in other parts of the country, though there is an incremental rise in "per kilowatt cost" when usage exceeds 1,000 kWh (kilowatt-hours) per month. That 1,000 kWh/month threshold is crossed by most 3+ bedroom homes in Florida, and it's the first thing a solar company will look to eliminate. After that, they'll try to get a home close to a zero monthly bill (excluding fixed utility fees) without pushing excess energy back to the grid. These calculations are achieved by understanding your utility usage (your bills), using PV Watts - a web application that can broadly determine how much energy a solar PV system can produce at a particular longitude and latitude, and more sophisticated tools that can identify roof pitch, roof height, trees and other obstructions (like the two-story home to your south) to provide an estimated per month / per year solar energy output. Ultimately, the homeowner will have the final say in what size system they would prefer. An alternative to sending energy back to the utility grid, mostly for free, is to add a backup battery to capture the excess solar PV energy and use it to power your home at different times of the day. It may only incrementally save you money in energy costs, though it allows you to oversize a system to achieve near zero kilowatt usage from the utility company month over month.
When a home is brand new, or recently purchased, calculating past usage will be challenging. If there is no solar currently or a solar PV system already exists, it might be best to wait a few months after moving in to collect some energy usage history before making any solar PV decisions. Gas appliances, insulation properties, total square footage and other factors may vary between a previous and current home. Incremental solar PV add-ons due to miscalculation or assumptions will be more costly and complicated than a system sized properly based on accurate data.
When estimating potential energy savings per month, the under/over 1,000 kWh threshold needs to be considered using a slightly more complex calculation. For example, if your average energy usage is 1,500kWh/month, and assuming your utility rate is $0.12 per/kWh under 1,000kWh and $0.15 per/kWh over 1,000kWh, a solar PV system that generates an average 600kWh per month will eliminate the over 1,000kWh higher rate completely and will cut into a bit of the under 1,000kWh rate. In this scenario, savings would average $85-$90 per month ((500 x $0.15) + (100 x $0.12)) for a small PV system with minimal shading and a fair azimuth (southeast-south-southwest).
Existing systems can usually be upsized should the family size grow or you bring home a new EV (electric vehicle), with a solar PV add-on down the road. Keep in mind though, that adding solar will require new engineering and permitting, and may require a new Interconnection Agreement with your utility, and potential electrical service equipment upgrades to accommodate the added solar energy production. Additionally, all solar PV installations are subject to the many Florida, NEC and Fire Building Codes and requirements that may limit the number of panels you can add to a home or building.
The Difference Between Daylight and Sunlight
This is an area met with persistent confusion. Think of daylight as what we all wake up to every morning and enjoy through the day. It allows one to sit on a swing under a live oak and read a book. Now think of sunlight as sitting in a chair in your backyard and not being able to rest your limbs on the metal arms of the chair because they're hot to touch. Or, doing what your mother warned you to never do; look up in the sky at that big round yellow ball. If you can see the yellow ball, you're looking at sunlight. If you're can't see the ball, or at least most of the ball you're looking at daylight.
Solar panels need sunlight to generate ample amounts of energy. More sunlight equals more energy. Panels will function with indirect daylight, though at a much lower output. Every solar inverter requires a minimal amount of voltage from a solar panel or panel array before it will begin converting that DC energy into usable AC energy. The inverter turns on in the morning when the sky has become bright enough to reach that minimal number and will turn off when the sky begins to get dark in early evening. The same will happen when clouds pass over, blocking sunlight. The amount of energy produced by a solar array midday will be six to ten times greater than the first and last hours of a solar day (the time a solar array is active and generating energy).
The wizards who work out these formulas have determined that on average, a Central Florida solar PV system will see a cumulative 5.5 hours of full sun per day. That may seem low, though remember it's an average over twelve months and takes into account cloudy and rainy days that often don't produce the equivalent of a single full hour of sunlight. We have found it to be a good conservative estimate. This number can be used to quickly estimate the potential output of a solar PV system, multiplying 5.5 x the total AC output of a system. Of course, azimuth, roof pitch and shading will all play into determining a systems actual potential. You can find the numbers for your region here.
Understanding AC and DC
Let's begin by revisiting some 4th grade science. There are two primary ways that electrical energy is transmitted. AC, or alternating current is what powers your home lighting, appliances, etc. It's fed into your home through a utility meter, connected to power transmission lines that originate at power generating stations. As all these power stations are connected together to ensure you always have an ample supply of energy, the utility electrical system in its entirety is commonly referred to as " the grid".
DC, or direct current is the energy that's stored in batteries, like those "AA" Duracell's in your kitchen drawer. A battery is what starts your car in the morning and keeps your cell phone working all day. Solar PV panels on a roof or in a backyard absorb sunlight and convert it into DC energy. Without a means to store this energy (a battery) wires transmit the DC energy from the solar array (a grouping of solar panels) to an inverter, or from each solar panel to a mini-inverter - commonly referred as a microinverter located under each solar panel. The inverter converts the DC energy into AC energy, which can then be used to power all those things in your home or business that require electricity; air conditioning, appliances, electronics and lighting. Because energy has to go somewhere and without a means to store it, any solar energy you're producing that isn't needed to power your home or business will be fed back to the grid through your utility meter. And because energy seeks the path of least resistance, the solar energy being generated by the solar PV system connected to your home or building will be consumed first before any energy from the utility company is needed. The utility meter will move in both directions throughout the day sending and receiving energy, depending on the size of the solar PV system and usage.
Now for the bad news. When solar generated DC energy is converted (inverted) into AC energy there is a significant loss. Some may argue this number up or down by a few percent, though the industry has settled on a 15% loss during conversion. It's the number every utility company uses when calculating the AC energy a new solar installation can potentially feed into the grid, assuming a site is utilizing none of that energy at a given time. The reasons for it get technical and we'll refer you to the works of Nikola Tesla and Thomas Edision for clarification. As it will never change, it's best to accept what is. What this means in real numbers is that the 10kW DC Solar PV system you purchased will only output 8.5kW AC energy. It's important to understand this number when trying to calculate your specific needs.
Roof and Ground Mount
A lot has changed over the past decade in the way roof mounted solar PV systems are installed. Back then, installers attached L-Feet (short aluminum L shaped brackets with a hole on one side for the mounting bolt and a slot on the other side to attach a rail) to a roof with a lag bolt and a glob of roof sealant. It worked most of the time, though there were occasional leaks. Flashings, thin pieces of metal that slip under a row of roof shingles, were added shortly afterward to divert water away from the L-Foot installation. It helped a bit. Today, the L-Foot has been replaced by a sort of upside down T-Mount with four holes for mounting at the base and a slot on the vertical portion for the rail. The bottom of the mount has a foam-backed mastic seal that's activated when you remove the liner. It securely attaches to roof shingles or rolled roofing, filling in any gaps or voids. When the screws are installed, some of the mastic material is pulled into the hole, adding additional protection at the point of penetration. The system creates a secure bond and minimizes installer error.
Tile roof installations have also seen improvements in recent years. Top mounts eliminate the need to remove and cut tiles to add roof attachments. Installers drill a 1.25" hole through the tile and insert a post with a similar foam-backed mastic on the bottom. Three screws at opposing angles are driven through the deck to secure the mount. A top flashing is added to help divert water away from the mount. While shingle, rolled roof and tile installations have seen improvements, a standing seam metal roof installation is the most trouble-free solution. A solar PV system can be installed with only one (for wiring), or no penetrations if preferred. Metal clamps are secured to the ribs of a standing seam metal roof, and the L-Feet, rails, etc. are attached to the mounts. Some metal roofs with trapezoidal type seams will require penetrations, though the penetrations are made with short self-tapping screws that pass thru a foam-backed mastic, sealing the hole and creating a tight bond. The mounts are toward the top of the trapezoidal seam, away from standing water. Metal roof panels made to look like slate tile or shingles require a tile hook attached under the metal panels, directly to the roof substrate. It should be noted that two-thirds of the roof leaks we investigate turn out to have nothing to do with the solar PV installation. The leaks are typically the result of unfilled nail holes or voids from the roof installation. While no one can guarantee zero leaks, with today's technology they are very infrequent. The thought of a potential roof leak shouldn't dissuade you from adding solar to your home or building.
Recent innovations have made it possible to add a solar PV system to flat commercial roofs with TPO or other types of seamless membrane roofing with no penetrations. Hollow aluminum blocks are mounted to the roof using expandable roofing cement. Solar panels are mounted directly to the secured blocks. The system meets all Florida wind-load requirements.
Ground mount installations have also undergone a significant change in the past few years. A ground mount is a metal racking system secured to the ground, with solar panels mounted and facing south at an appropriate angle. It's an option for those who don't want solar panels on their roof, or have an abundance of underutilized property. In the past, a ground mount had to be secured to the ground using lots of concrete, sometimes up to four-feet deep. It was an expensive and time consuming process. Today, ground mounts can be installed using ground screws - three-foot long cork screws that are driven into the ground with a piece of heavy equipment. An entire ground mount system can now be installed in a single day. Something that used to take a week. Ground mounts are subject to zoning limitations, property setbacks and other conditions. You'll also need a large open area free of trees and other obstructions that would cause shading. A ground mount installation will be more expensive than a roof mount, so you want to be sure the solar generating conditions are optimal to ensure a good return on investment.
The Best Solar Panel
I don't think anyone can answer this. Sales reps may suggest one panel over another, possibly because their margins are better - not because the panel is better. Most every solar panel made today comes with the same performance guarantee (80+% after 25 years), so they're all about the same. A few manufacturers may boast a slightly higher efficiency, though those panels typically cost more, so the net gain is close to zero. Today, there are more than a hundred solar panel manufacturers worldwide with hundreds of different models. Don't be over concerned with the brand of solar panel used in your solar PV system. Any brand will likely last the full length of their expected life (25+ years), unless they're hit with golf balls, a heavy hail storm or… a model airplane. We haven't seen a solar panel that hasn't produced at or above its nameplate rating. And out of tens of thousands installed, only a small handful have been replaced due to warranty claims - less than one tenth of 1%. Generally speaking, solar panels are very reliable.
Inverters and Microinverters
There are two different technologies used to convert DC energy generated by solar panels into usable AC energy. String inverters have been around since the birth of the solar PV industry. They're called string inverters because the panels on the roof are strung together like Christmas lights, and like Christmas lights often when one has a problem the entire string stops working. Bummer. Like the positive and negative ends of a AA battery, each solar panel has a positive (+) and negative (-) wire. Each panel is strung to the next, positive to negative, positive to negative and so on until you are left with one positive wire at the last panel and one negative wire at the first panel in a string. Those two wires feed down from the roof to the inverter where they are converted to AC energy. Inverters come in all different sizes; 3kW, 5kW, 7kW, 10kW. For commercial installations, they're huge with sizes as large as 120kW at 480V, capable of handling several hundred solar panels. The size of an inverter is always represented in AC kilowatts (1,000 watts = 1 kilowatt or kW), after adjusting for that DC to AC conversion factor. One primary problem with inverters is that a string won't turn on until the cumulative total of watts in the string has reached a minimal level. This number is typically measured in volts, though we'll use watts here to simplify the explanation. Say you have a string of ten 400 watt solar panels. In full sunlight, they would be outputting 4,000 watts (10 x 400). The inverter may require a minimum level of 1,500 watts before the string is allowed to feed energy into the inverter for conversion. This is necessary to prevent the inverter from constantly flicking on and off as the sun rises or sets, or a cloud passes over. Imagine it's like a toddler flicking the light switch in your hallway on and off hundreds of times. That switch is going to fail sooner than expected. Strings have to be kept close together and at the same orientation on the roof to ensure all the panels in the string receive the same amount of daylight in the morning to turn them on as quickly as possible.
SolarEdge, a leader in the solar inverter industry solved part of the inverter problem with the advent of optimizers. One of these devices is placed under each solar panel in a string, and they're able to temporarily boost the energy from low-producing panels to trick the inverter into thinking the string has reached the minimum output level. This trick can turn a string on 15-30 minutes sooner and keep it on as long in the evening. The result is incrementally improved overall performance. Remember, solar arrays produce less energy in early morning and early evening.
Enphase started offering microinverters in 2008. As a relatively new technology, their growth was slow in the early 2010's, though their popularity went through the roof in 2017 when the National Fire Code was revised to require "Module Level Shutdown" for all residential solar installations. Solar panels generate DC energy as soon as they're exposed to the sun. The inverters do the converting, though the wires feeding into the inverters are live, even after the switch for the inverter has been turned off. It's a hazard for firefighters battling a fire in daylight on a roof with wires carrying potential lethal energy levels. Rapid Shutdown at the module level is required for all solar installations. Inverter manufacturers like Tesla have gotten around this by installing small RSD's (Rapid Shutdown Devices) under every two or three panels, which are designed to cut off DC power between the solar panels in an array when a signal from the inverter is lost (when it's powered off). This technology works, sort of, though these RSD's can be troublesome as when one fails you need to work through an entire string to find the problem. The SolarEdge optimizers were already a solution for module level shutdown as they cut power to each panel when the inverter is powered off. It resulted in SolarEdge picking up the lion's share of inverter installations since 2018.
Microinverters are mini-inverters mounted under each solar panel. The positive and negative wires from the panel plug directly into each microinverter, which is plugged into a trunk cable with multiple drops. Depending on microinverter output, each trunk cable can have 10 to 13 microinverters connected. There are several different Enphase models available today, outputting from 290 to 425w AC, if coupled with an appropriately sized solar panel. The energy in the trunk cable has already been converted from DC to AC by the microinverter, so only AC power is fed off the roof to a Combiner box near your utility electric meter with a circuit breaker for each microinverter circuit (up to four) and a Gateway that monitors the microinverters performance. It's a simple, very reliable technology. When power to the house is turned off, only the short leads from the solar panel to the microinverter (under the panel) are live with DC energy. Firefighters are safe. Microinverters are each independent, so one panel can be shaded by a chimney while all the other panels around it are producing at full power. They are the most popular medium for residential solar today. Enphase has recently entered the commercial market with 208v and 480v three-phase microinverters, outputting up to 580w. It's created an alternative option for commercial and industrial solar installations. When an inverter or an inverter string goes down, you're losing all or a good portion of your solar output. When a single microinverter goes down, you've lost a single panel for a couple weeks before it can be replaced under warranty (25 years).
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Inverters and microinverters must be connected to the utility grid to power on. Without the presence of the grid, during a power outage the inverter / microinverters will power off. As energy generated by the solar panels "must" go somewhere, without a battery to store and regulate that energy, the solar PV system is disabled to protect its components and your home appliances. Yes, your PV system can generate energy in daylight during a power outage, though the amount of energy being generated will be unregulated, bouncing up and down as clouds pass overhead. It's like that toddler and the light switch. Your refrigerator and other appliances wouldn't like it. Powering your PV system off is the safe approach.
Inverter Clipping
All inverters and microinverters have an AC output threshold - the maximum amount of AC energy they can deliver to your home or the grid at any given moment. When the DC energy being input to an inverter or microinverter exceeds that threshold (after DC to AC conversion) that excess energy will be throttled back or clipped. Nothing can change that. Your inverter/microinverter has a maximum amperage rating which determines the size of your fuses or circuit breakers during installation. If a salesperson tells you otherwise, they're not being truthful.
For example, a 10,000-watt DC PV system on a roof with a capability of outputting 8,500 watts AC (after conversion), connected to a 7,600 Watt AC inverter, will clip each time that rooftop system reaches the 7,600-watt AC threshold. We have the advantage of viewing data for hundreds of active PC installations and have seen systems on bright sunny days that will reach their maximum output and stick there flat lined for a few hours before the sun starts to set. As a note, inverters generally like to operate at or near maximum capacity, so oversizing an inverter to overcome this shortcoming is not recommended. Finding the right balance of panel count/wattage and inverter size is the preferred approach. There are certain instances where an undersized inverter may be justified: one or more strings facing north or northeast/northwest, or heavy shading, where maximum output may only occur occasionally. It allows the inverter to operate in the upper third of its capacity most of the time. Though, if you have a good shade-free south facing roof, make sure your inverter is properly sized for your solar panel system. An honest solar installer will ensure that it is and not try to low-ball a quote with an undersized inverter to close a deal.
Microinverters have the same limitations. If you couple a 420-watt DC solar panel, capable of outputting about 357w AC after conversion, with a microinverter that has a 320w AC max output, that panel, despite its size will never produce more than 320 to 322w AC. Note this maximum output assumes ideal conditions; a good south facing roof, typical roof pitch and minimal shading, though rest assured east/west facing arrays will reach maximum output for at least part of a day. A system with 420w panels would do better with microinverters capable of outputting 349w AC. Payback in energy savings for the slightly more expensive microinverter is typically 3 to 5 years. Be sure your solar quote includes specific models for your solar panels and inverter/microinverters. You can request data sheets or look up the information yourself on the Internet. Look for Maximum Continuous (AC) Output Power to determine what your system will be capable of outputting.
The takeaway here is the DC wattage of a solar PV panel is only one part of the equation that makes up a well-engineered solar PV system. Don't simply look for higher wattage panels without ensuring all the other equipment; inverters, microinverters, backup batteries are matched to work together efficiently.
Meters, Mains & Meter-Mains
Every home or building connected to the utility grid has an electric meter that measures the energy being delivered to the site, and with a solar PV system can also measure any energy being sent back to the grid. You'll find the meter somewhere outside your home where the utility company has unhindered access.
Electric meters will either be stand-alone, meaning that the meter is in its own enclosure with a separate cabinet to house all of the circuit breakers for your home or business, or will be in a meter-main combo cabinet where the meter, your main circuit breaker and some additional circuit breakers are located. The former makes installing solar PV systems easy while the latter adds a restriction to the size of a solar PV system. As meter-main combos are less costly for builders to install, you'll find them in most every home built over the past several decades.
Meter-main combos typically come in two sizes - with either a 200Amp or 150Amp main circuit breaker. The meter side of a circuit breaker may have more than 1,000A of electricity available, though the main circuit breaker (200A or 150A) will limit what can safely pass through to your panel. Most meter-main panels share the same busbar rating of 200A to accommodate either size main circuit breaker. The busbar is a metal strip that all the circuit breakers snap into. Occasionally, we may find a busbar with a rating of 225A. That's a good thing. The National Electric Code says that a 200A busbar can accept up to 120% of its rated load. That means a meter-main combo with a 200A main breaker can accommodate up to 40A of solar PV energy. (200A x 120% = 240A). If a home has a 150A main breaker, the busbar can accommodate up to 90A of solar PV energy (240A - 150A = 90A). It is possible to sometimes derate a 200A main circuit breaker to 175A, which would allow for additional solar, though some municipalities make that transition difficult. The size of a main breaker when the home was built is determined by a complex calculation that includes square footage, number of bedrooms, appliances, HVAC calculations, etc. Typically, none of these criteria ever grow smaller, limiting the justification to reduce the size of the main breaker.
Something new called PCS, or Power Control System developed by inverter/microinverter manufacturers can electrically throttle back an oversized PV installation when the software senses the busbar is approaching its maximum capacity, though to date it has not been approved for use by any Florida utility companies. For now, Floridians have to work within the National Electric Code requirements. For reference, a 7,600-watt inverter will require a 40A solar breaker as will two (20A per) microinverter circuits of 10 to 12 panels. That's the typical limitation for a meter-main panel with a 200A main breaker. In reality, no Florida home will ever come close to needing 200A of energy, unless they've built an ice rink in their backyard. Though these are the rules that must be observed.
For larger homes with two 150A or 200A main breakers, or homes with a separate meter enclosure and main panel, solar installers can do a supply-side-tap, which connects the solar energy to the wires "before" they reach the main circuit breaker and busbar with its limitations. With that scenario, there's really no limit as to how much solar PV can be added to a home or business. If you have a meter-main combo restricting your ability to add additional solar PV or battery backup, the solution today is to replace the meter-main combo with a separate meter cabinet and main panel. It adds additional costs to an installation, though it allows a homeowner to add whatever they choose, now and in the future.
Monitoring
All solar PV systems being installed today include some sort of Cloud based monitoring platform. The monitoring is associated with the inverter or microinverter brand, not the solar panel installed on your roof or in your backyard. In the past many inverter brands didn't offer monitoring, or did via an expensive add-on module to connect via Ethernet or Wi-Fi. It's near impossible to get an old 2015 inverter connected to a monitoring platform today if it hasn't been connected previously. Homeowners can still get a limited view of their system status through a small display screen on the front of the inverter. Those systems require a truck roll for service technicians to figure out what's wrong with a system, and typically a second visit to resolve an issue. Remote access to a system saves time and money.
Enphase, AP Systems, Tesla, SMA, SolarEdge, Goodwe and many other brands all offer their own proprietary monitoring platform, giving installers full access, and owners limited access to view pertinent data. Connectivity to the monitoring platform is achieved via a connection to the homeowner's router with an Ethernet cable or through Wi-Fi, which are both built into each inverter/microinverter Gateway, or via a cellular connection with a $400-$500 modem that needs to be renewed every five years. This Cloud connectivity allows installers to analyze performance, pinpoint the exact time a system or panel stopped producing and allows them to open warranty cases, often resolving issues without a truck roll.
Inverter systems can only provide an overall view of each inverter - typically one or two inverters in a home installation. If one or more panels, or a connection between panels fail, it will often flag an error message to the inverter and require a technician to troubleshoot an entire string on the roof. Pinpointing a problem is tedious and time consuming. In other instances with maybe twenty-four panels connected to an inverter, one or two panels on the roof may not be working at all and no one will ever know without testing the voltage for each individual panel - an expensive and laborious process. You can try testing a string of ten 400w panels on a bright, sunny day without any shading to determine if you come close to 4,000 watts (10 x 400), though that's a guess at best. A reading of 3,500 watts can lead a technician on a wild goose chase with no conclusions after three hours on a roof. It's problematic and another reason string inverters have fallen out of favor with most installers and homeowners.
Enphase microinverters monitor each individual panel on a roof. They can display how much energy each panel is generating. If a lower output can't be explained due to shading from a plumbing vent, tree branch or other obstruction, it's possible the solar panel is underperforming and may qualify for a warranty claim. Panel manufacturers will ask for Enphase microinverter data to validate the claim - something you can't do with an inverter system. If a microinverter fails to report, Enphase can try to jump start it remotely and determine if it's a micro or panel problem. Often, their remote analysis will result in an RMA for replacement without an installer leaving the comfort of his office chair. SolarEdge offers similar performance and troubleshooting metrics with their optimizers connected to one or two panels, though the Enphase system is considered best in class. Connecting to the Enphase Cloud via Wi-Fi is the preferred method as it updates data every fifteen minutes and can perform tasks like firmware updates remotely. Cellular connections are limiting and should only be used as a last resort.
System Maintenance
While solar PV systems can provide years of trouble-free performance, there may be instances when your system will require maintenance. It's important to choose an installer who will be around if and when you need help with an issue. A request for service may have to do with a roof leak, or be the result of damage from a storm or lightning strike. Or, it can involve a warranty issue, We've even seen instances of rodents making homes under solar panels and chewing on wires to pass the time, creating havoc for both homeowners and technicians. Whatever the reason, a trained service technician will have the knowledge to help solve your problem. If contacting your original installer, they'll have access to view your system remotely to identify issues before a truck roll, which may help to reduce the cost of the service call. If not, you'll need to grant a new solar company access to view your system through your inverter web portal. Having access to view a system is required before touching any PV system. It verifies what was and was not working before any work is performed.
Panel cleaning is another service your solar installer can provide. New neighborhoods don't have many trees to blow pollen around, though more established communities have plenty. Rain cannot wash the pollen and grit that collects on solar panels. Look at a black car that lives outside after a few months. Periodic cleaning is needed to ensure optimal performance from your solar PV system. Homeowners can clean panels themselves, though we don't suggest anyone other than trained solar service technicians traverse the angles of a shingle or slippery metal or tile roof. Don't use a pressure washer to clean solar panels. It will damage the glass surface and push water through the seals designed to prevent water penetration. You'll need a brush and long handle used to clean trucks and RV's along with a bucket of water mixed with Dawn detergent to scrub each panel, and a garden hose to rinse afterward. The Dawn won't damage your roof or vegetation, and may even keep insects away.
Anyone who lives in Florida knows their thirty-year roof shingles will only last 12 to 15 years, so there will be at least one solar removal and reinstall throughout the life of a PV system. Most panel and microinverter manufacturers "require" that systems be uninstalled and reinstalled by a licensed and certified solar installer. Don't let your roofer talk you into letting them tear your system apart. We have seen the remnants of systems that look as though the flying monkeys in the Wizard of Oz removed a solar roof mounted system, leaving parts strewn about like the poor scarecrow. Your solar installer will remove the system properly, mark and label everything and reinstall your system, ensuring everything is working as it should. Note that removal / reinstalls require all new roof mounts and attachment hardware. The only things reused are the panels, rails and wiring. If switching from shingle to a metal or tile roof, new engineering will be required.
Purchasing, Financing & Leasing
Adding a solar PV system to your home or business is a big investment. Educating yourself is critical to ensure a properly designed investment will pay for itself, with dividends in the years that follow. For those from New York or New Jersey, in the immortal words of Sy Syms, "An educated consumer is our best customer." Don't be misled by slick salespeople who make verbal promises. And never allow yourself to be pressured into making a decision this important. A week or even a month won't make any difference. The industry has been plagued by unscrupulous solar companies whose primary interest was to make a fast buck. Like the tides, many have come and gone leaving unhappy customers in their wake. It's always sad to hear their stories. Don't get duped. Alright, the sermon is over.
After settling on the type and size of solar PV system you require to meet your needs, you'll need to decide on how it's going to be financed. Cash, of course, is always preferred, though $20,000 to $30,000 is a large chunk of money. If it's accessible though, it's not a bad idea. Consider that a 10-year CD will yield about a 4.25% return per year. In contrast, a properly designed solar PV system can reduce or come close to eliminating your electric utility bill (not including fixed fees and taxes) with an estimated ROI of 6 to 8% today, and more in the future as utility rates continue to rise by an average of 1 to 3% per year. Can anyone expect interest rates to increase by 10 to 20% over the next ten years? Aside from the utility cost savings, the solar PV system will add value to your home, while, at least in Florida, it won't increase your property tax assessment. Do your own calculations, or speak to your financial planner before making any decisions. Educate yourself.
If cash isn't an option, with a credit rating over 700, solar financing is available with an average 6% to 8% interest rate and 12 to 15-year payoff. Most financed systems offer terms of $0.00 down, so there's no up-front costs to go solar. A homeowner can opt for a hybrid payoff with a cash deposit and smaller monthly payment or shorter term. There are plenty of options, even for homeowners with not so great credit. In the past, when the Federal Tax Credit for solar was available, solar sales reps would often twist words to make potential buyers believe they were getting a tax refund, not a tax credit. With thoughts of that big fat check swirling inside a potential buyers head, the sales rep would ask to run a credit check. The amount of financing offered to the homeowner by the finance company would determine the size system that would be pitched, regardless of the actual need. It was another black mark for the solar industry. If a solar company asks to run your credit "before" you've settled on a complete system with defined size and components, escort the rep from your home or hang up the phone. You may possibly be dealing with a grifter. While the elimination of the Federal Tax Credit has removed an incentive to add solar to your home or business, it's slowly eliminating the solar sales rep and their 20-30% commission on the system sale price, clearing the way for honest solar companies to do what they've always done. Offer solar PV systems at a fair price for homes and businesses that would benefit from the potential utility cost savings.
Finally, there's leasing. In theory, leasing seems like a good idea. No up-front costs, just like financing, and a lower monthly payment because the lease terms may be 20, 25 or even 30 years vs. 12 to 15 for financing. There's a 25-year warranty on much of the solar equipment, and the leasing company is responsible for maintaining it, right? What could possibly go wrong? Hmm. In the past few years, several of the largest solar leasing companies in America have filed bankruptcy, leaving tens of thousands of existing leaseholders with no one to call and nowhere to turn. New finance companies sprang out of nowhere to assume these existing leases, continuing to debit bank accounts monthly. These newly formed finance-first entities have no infrastructure to deal with homeowners solar issues - no maintenance or service arms to remedy problems. Hundreds of these homeowners are currently trying to get their systems serviced and their requests have been mostly ignored. Search out these now defunct solar leasing companies on the Internet and look at the hundreds of BBB comments left by furious and frustrated leased-system homeowners. A few hours of reading should be enough to convince you this is not a good approach to going solar. Even for the leasing companies still operating, you can expect to pay up to three times the original cost of a system over thirty years. We've talked here about many homeowners opting to upgrade or replace their systems. Add-on solar PV systems, or in some cases, battery backups can't interfere with an existing leased system the homeowner "does not own". So additions must be installed independent of the leased system. And forget about replacing a system with something more efficient after 15+ years. You're stuck with the system for the entirety of the lease, unless you choose to buy out the lease. Another added cost. Most leased-system homeowners opt to pay out of pocket for equipment warranty repairs (for travel and labor) or to remove/replace panels when dealing with a roof leak, rather than waiting months to get any satisfaction from their leasing company. We don't offer solar leasing and never will. Sadly, it's a hard lesson that many homeowners have had to learn.
Warranties
Rooftop and ground mount solar products have some of the most generous warranty polices, extending to twenty-five years or more. It's the result of years of research and refinement, culminating in products that will outlast their warranties. Solar panels sold a decade ago from a handful of large, well-funded manufacturers have had occasional issues, though more recently failure rates have dropped to something well less than 0.0002% - infinitesimal. Typically, solar panels being sold today will come with 25-to-30-year performance warranties, and product warranties ranging from 10 to 25 years. Depending on manufacturer, a performance warranty will ensure the panels will output approximately 81-87%% of their original nameplate rating (1 to 3% in Year 1, and .5 to .7% for subsequent years) through the warranty period. Product warranties will cover physical components of the panel, though they will not cover things like, lightning strikes, golf balls, quarter-size hail… or model airplanes. The glass used to manufacture solar panels has gotten much stronger than it was ten years ago, so most of these concerns are uncommon today. NOTE: Don't dwell too much on a particular brand of solar panel because of its warranty. The truth is, there's a good chance you'll want to replace your panels before the warranty expires. A 4.95kW, 165w-30 panel system sold 15 years ago, can be replaced in the same footprint on your roof with an 8.80kW 440w-20 panel system today. Considering performance degradation, that's twice as much output in the same space.
Solar inverters typically come with 10-to-12-year warranties, some extending to fifteen years. Many have outlasted their warranty, though we have seen a good number of older inverters that required warranty replacement. Like solar panels, inverters continue to improve longevity. Microinverters and optimizers (used with SolarEdge inverters) both come with generous 25-year warranties - uncommon for an electronic device that will be up on a roof with extreme weather conditions. In our experience, for the tens of thousands we've installed, warranty replacements are rare, totaling a few dozen per year, or about a 0.0004% failure rate. Because of today's advanced web-based solar monitoring platforms, an installer can often request a warranty replacement on a customer's behalf with a few mouse clicks. That helps to reduce costly troubleshooting truck rolls. It should be noted these warranties only include replacement of components. They don't cover travel time and labor to remove/replace the defective component. Other electronic components that comprise a solar PV system typically have five-year warranties, while mounts, rails and metal attachments will come with 25-year warranties. Aluminum and stainless steel will last a very long time.
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As battery backup technology continues to expand and the market becomes more competitive, manufacturers are now offering product warranties of 12 to 15 years, or more in some cases. Aside from the battery, other components will typically have warranties from 5 to 12 years. In addition to the battery product warranty, like solar panels a performance warranty is included based on the total charge/discharge rate over the warranty period. Typical energy retention is 70% of the battery's rated capacity at the end of 12 or 15 years. I bet we all wish our cell phones came with that kind of warranty.
Solar installers will generally provide a workmanship warranty of one to several years. That typically covers roof leaks, equipment installation, electrical connections, etc. As solar components have become more dependable, future system issues may often be attributed to installation deficiencies. When choosing a solar installer, look for a company with a solid reputation and experienced technicians. When you purchase or lease a system from a large, national solar company with a pushy salesperson, they'll outsource your installation to a local sub-contractor that you'll never see again after they drive away. Do your research and be well-informed before making any solar investment.
There are solar insurance companies out there, like those home appliance warranty companies, who will extend your meter to panel warranty beyond the solar installers' workmanship warranty period. We have no experience with these providers, though we've all read horror stories of people waiting weeks to get their refrigerator repaired. If something presented to you sounds too good to be true, it probably is. After all, insurance companies are in business to make money - not give it away. When searching out a solar provider for a new installation, or an existing system in need of service, look for a company that will respond and get working for you with a single phone call or email. Your time is valuable.
Battery Backup Systems
Battery backup systems have evolved over the past decade. It's a fast moving technology that continues to expand and improve. We won't get into the advantages of different battery chemistries in this article, and nor should you. Rest assured that the companies researching and developing these new and improved batteries will offer the best and safest systems available in order to gain your business and trust. It's become a very competitive market.
Battery backup systems come in two flavors - DC coupled and AC coupled. And let's add Hybrid, a combination of both technologies. Each battery system has two primary components: the storage battery or batteries, and the Controller; also called an aGate, Combiner, Gateway, etc. The batteries for all these systems are basically the same - a large storage device that can input and output DC energy. What differentiates each battery backup brand and system type is within their Controller design. All battery controllers can form a microgrid, basically a mini-version of the vast utility grid, within your homes energy system. It tricks solar components into thinking the utility grid is present. As the controller can regulate how much energy your home requires, second-to-second, it will provide power within its limitations for household circuits, appliances, etc.
DC coupled battery system controllers include an integrated solar inverter. So the DC energy from the solar panels feed directly through the controller into the DC storage battery, and as required will be converted by the controller/inverter into AC energy to power your home or feed back to the grid. Because energy generated by the solar panels has to go somewhere, if the battery is at full capacity, and the home's energy needs are fulfilled, excess energy will feed back to the grid. During a power outage with no utility grid present, the controller may throttle down or turn off the solar inverter if there's no place for the excess energy to go. It's a balancing act that the battery controller will manage continuously. Generally, DC coupled battery controllers are not capable of converting AC energy from the grid or a generator into DC energy to charge the battery, limiting their capability.
An AC coupled battery system can input AC energy from multiple sources: the utility grid, a generator or from a solar array that has already converted DC energy into AC energy via an inverter or microinverters. This AC energy must then be converted to DC energy before it can be stored in the connected battery. This conversion from AC to DC, and then back from DC to AC when power is output from the battery comes at a cost. When looking at AC coupled battery spec sheets you'll find an AC-round-trip efficiency rating, usually around 90%. It is what it is. Because an AC controller can accept input from multiple sources, it's a more versatile solution for your backup system. In fact, with an AC controller you don't need a solar PV system to store and generate energy during a power outage. You can accomplish that with a fully charged battery from the grid before the outage and a generator while the grid is down.
A hybrid backup battery system combines both technologies, with an inverter to convert DC solar power to AC and inputs for: AC coupled solar power (from an existing inverter or microinverters), the utility grid and possibly a generator. Hybrid systems will have limitations relating to the ratio of DC input solar power vs. AC coupled solar power, which will affect how much energy will be allowed to pass through the controller during a power outage. Note that DC coupled and hybrid battery backup systems with integrated inverters are subject to the same parameters as all inverter type solar PV systems. Solar panels are connected in strings like Christmas lights, so they can't be monitored independently, and RSD's (Rapid Shutdown Devices) need to be installed under every, or every few panels to deenergize the DC power from the roof in the case of a daytime fire or emergency.
Each storage battery has a limit as to how much energy can be input when charging, typically between 5kW & 8kW DC energy. So a 14kW solar PV system on your roof can't be coupled with a single storage battery. Otherwise when daylight changes to sunlight, the battery controller will sense that too much power is being input and the charging will be shut down, preventing your battery from being charged in an off-grid (power outage) situation. That would not be a good thing. The battery backup system would either need additional batteries to evenly distribute the energy from the solar PV system, or part of the solar PV system would need to be load shed - allowing it to work normally to power your home when the utility grid was up and running, though would shut down during a power outage.
All backup battery platforms offer monitoring capabilities, either integrated within their inverter or microinverter web portals, or stand-alone for battery-only manufacturers. Systems can be setup with several working modes: Self-Consumption, Time of Use (TOU) and Emergency Backup or Storm Guard. For each of these modes, minimum and maximum thresholds can be set to ensure there's always some juice in the battery for unexpected circumstances. In some parts of the USA, especially out west where energy costs can vary from $0.10 per kWh late at night to $0.30 per kWh at mid-day, Time of Use mode is very helpful. Homeowner with AC coupled battery systems can charge their battery late at night directly from the grid when energy is at its lowest rate and discharge the battery during peak hours when there isn't enough energy being generated by their solar PV system to handle the homes electrical needs. In Florida, utilities can't charge consumers based on TOU, though they all apply the under/over 1,000 kWh/month tiered billing. Homeowners will typically opt for Self-Consumption mode. This mode will charge a battery with excess (not needed by the homes electrical system) solar generated power during the day and discharge the battery in the evening after the sun sets. It prevents any excess solar PV energy from being sent back to the utility grid at nearly $0.0 cents, saving homeowners a few kWh each day. That's a good thing. Though using your available solar PV energy simply to get your battery to 100% every day and then discharging to 20-30% every evening is not recommended. Remember that 10% loss for AC to DC, back to AC conversion. A full charging/discharging scenario will cost you money, not save it. By monitoring your battery charge/discharge rates per day, you'll be able to set your battery min/max thresholds to maintain an efficient balance. Storm Guard is a feature most battery manufacturers have integrated into their monitoring software. Their web portals monitor NOAA weather reports, and when severe weather is approaching your area, the battery controller will automatically shift into Emergency Backup mode to charge your battery to 100% with any means possible: solar PV or the utility grid. It's good to have fully charged batteries before a storm hits, even if it's a false alarm.
Most AC coupled and hybrid battery backup systems will accept a generator input, providing another means to charge a battery. If you have a generator, or plan to get one that's an important consideration. Battery systems also incorporate Smart Circuits, which can control some of the largest loads in a home, like your air conditioning compressor and hot water heater - powering them off as soon as the grid goes down (power outage). If your power goes out in the middle of the night or while you're out, these energy hogs can deplete your battery quickly. A battery backup system is a significant investment, so understanding how everything works will help to eliminate future surprises. Knowing you'll still have power if the grid goes down will give you peace of mind. Battery backup systems can be incorporated into any new solar PV system installation, included in a solar PV add-on or upgrade, or an AC coupled battery backup system can be added to any existing solar PV system. You can even add a battery backup without any solar. There are plenty of options.
Sizing a Battery Backup
Like trying to size a solar PV system, determining the size of a battery backup system will depend on personal preference and how much money you're willing to spend. Comfort and convenience can get very expensive. Not long ago, when battery backup systems were in the 5 to 10kWh AC capacity range, most homes needed a critical or essential load panel - a panel next to your main electrical panel filled with the circuits that were most important to you during an extended power outage; refrigerators, ceiling lights and fans, and some electrical outlets. These were the only circuits connected to the battery backup system. The small battery systems were constrained by the amount of amperage they could discharge, limiting their ability to power on air conditioning or other heavy loads. An air conditioning compressor may only need 30 Amps of energy to run, though it might need as much as 65 to 70 Amps for a few seconds to turn on. It would take two or sometimes three batteries coupled together to maybe get an AC system to work. When the power went out, the battery backup would try to turn on and if it sensed the load was too great for the battery systems capacity, the entire system would turn off and reset after five minutes, leaving homeowners in complete darkness with their $25,000+ battery backup system. It was not a good thing. Today, most battery systems start at 15kWh AC, and the circuitry has been reconfigured to provide as much as 48A of continuous power, and as much as 85A+ for 10 seconds to start up those heavy loads. Although that one battery can theoretically turn on your air conditioning, it's still not a good idea. Read on.
All homes are now configured as whole home backup, eliminating the cost to install an essential load panel. But as soon as that battery backup kicks in after the power goes out, assuming your battery was at 100%, you're now down to 99% and counting… down. There are two ways to look at a battery backup system. Treat a power outage as if you're on a camping trip with only the necessary essentials to make things comfortable for you and your family - kind of treating it like an adventure. Or demanding all the comforts you're accustomed to; air conditioning, hot water, cooked meals, etc. With the prior scenario you may get away with a single battery, and with the latter you'll need several. Keep in mind that even in Florida, extended power outages as a result of hurricanes are rare - typically once every few years. Outages after a heavy storm may only last a few hours or most of a day. If you start thinking of conserving power as soon as the grid goes down, you'll make it through these energy inconveniences. Your installer may ask you to complete an energy survey to determine your actual wants and needs during a power outage. Most everyone will fall into the one or two battery system. If your determined to not have to make compromises, some battery controllers can support up to fifteen batteries in parallel. The only limitation is one's ability to pay for it.
But wait, I have a thirty-five-panel solar PV system to charge my batteries, so what's the problem? Well, the typical moderately sized home in Florida consumes an average of 1,400kWh of energy per month. A larger two-story home with four bedrooms may consume as much as 2,600kWh/month on average. That's 47kWh and 87kWh per day, respectively. Now that big 15.0kW DC, 12,75kW AC system on your roof can either power your home OR charge your batteries when the grid goes down, though it can't do both at the same time. A single battery may have total usable energy of 13.5kWh, two batteries = 27.0kWh, three batteries = 40.5kWh. See where this is going? If a hurricane does hit, expect a couple cloudy overcast days to follow, limiting your solar PV systems generating capability. Conservation is key. An alternative to adding a plethora of batteries is to supplement your solar PV and battery backup systems with a generator. Run the noisy generator during the day so you can charge you battery and have a quiet restful night with your home running on battery power. It's important to make certain the battery backup system you choose can accommodate a generator connection capable of charging your battery. That's a key feature today and for the future.
Another battery backup sizing consideration relates to the size of your existing solar PV system, or any planned future system. During a power outage, a single 15kWh battery can input/charge up to 6kW of AC PV power continuous and up to 7.5kW AC for a brief period. Accounting for any solar PV energy your home is consuming, if the excess solar PV power being generated to charge your battery exceeds these numbers, your controller will turn off your PV system completely, waiting for the battery to discharge to a pre-determined level before attempting to turn your solar PV system back on to power your home and charge your battery again. When the grid is up, the issue goes away as excess energy from the PV system is diverted through your reverse meter to the grid. For larger PV systems, this potential concern can be avoided by adding an additional battery, doubling the amount of solar PV energy that can be diverted to charge your batteries during a power outage.
It should be noted, that in the past battery backup systems were sold as being expandable at some future time. As battery system technology is changing so quickly, this has proven to not be a good approach. Enphase is on their 4th battery generation, Tesla is on their 3rd and Franklin is on their 2nd generation, all within a span of less than ten years. Companies will say their systems are backward compatible, though there are additional costs and compromises that may need to be made in order to mix any older generation and new equipment together. The best approach is to plan effectively and just get it done.