There are a myriad of inverter manufacturers and we have learned from experience which are reliable and durable. There are different inverters that are best suited for different applications i.e. smaller/larger installations, off-grid/micro-grid systems, simple vs complex roof angles, space availability, sun exposure/shading issues, electrical service panel space availability. These are only a few of the things to consider before investing in inverters, along with efficiency, reliability and warranty.
Below is a description of the different brands of inverters we like to work with. We’ve also included basic warranty information for the various manufacturers with links to their specific policies.
String inverters monitor the production of a system as a whole (as opposed to the production of each individual solar panel). Unfortunately, this means that if a single panel is shaded in a string, the production of the whole string goes down or, potentially, off. Additionally, for fire safety, a law was passed that requires all solar systems to have an emergency shutdown system at the panels themselves or on the roof so firemen can safely navigate the rooftop without risking electrocution. String inverters require the installation of an additional rapid shutdown system (whereas micro-inverters and optimizers have the system built in). Each manufacturer has taken a different approach to this rapid shutdown system (which is detailed below), but this adds an extra element to the installation and additional labor costs, which can be seen as a deterrent. However, string inverters last longer than micro inverters partly because they are more protected from the elements. Because string inverters can be installed in sheltered spaces like garages or next to the meter, they don’t have to endure the extreme temperature fluctuations that micro-inverters have to withstand on roofs.
SMA is an extremely reliable company that has been around a long time and has an inverter model to accommodate large installations. Their inverters have a 97-98% efficiency rating and have two rapid shutdown options. The first involves installing one optimizer at the end of a string that has the emergency shutdown system, the other requires installing a multiple part rapid shutdown system that has an extra feature allowing a small part of the solar array to keep working so you can have 2000W of energy at your disposal during a grid outage when the sun is shining. (Though this isn’t much power, it’s enough to charge a phone, plug in a few lights or an energy efficient fridge during daylight hours.)
SMA has a 10 year standard warranty and a 20 year extension warranty. The warranty covers shipping costs, repairs/replacements and labor.
SMA is a German company and has been in the solar industry since 1981. SMA inverters were manufactured for the American market in Colorado for many years, but recently moved that manufacturing facility back to Germany.
String Inverter with Optimizers
String inverters with optimizers allow for monitoring on each solar panel, more production from partial shading, and are more efficient than micro-inverters. They have less complex electronics on the roof which also means they have a lower failure rate.
SolarEdge is the only manufacturer that makes a string inverter with an optimizer. This system has an automatic shutdown built in in case of emergencies and are a great option for installations with sun exposure/shading issues or complex roof angles. SolarEdge makes a model to accommodate large installations, however, their average model requires a minimum of eight panels to operate. SolarEdge’s inverter is the most efficient on the market coming in at 99%!
SolarEdge was founded in 2006 and their inverters are manufactured in China.
Tigo Energy continues to improve their optimizers and are now working closely with SMA. Like other optimizers they improve array and inverter efficiency, and offer individual panel monitoring and rapid shutdown. The highlight of Tigo optimizers is that they can be coupled with any inverter.
Tigo was founded in 2007 and has a 25 year warranty covering shipping, parts, replacements or credit for the ‘residual market value of the equipment’ (Tigo does not cover labor).
Micro-inverters allow for monitoring on each panel, which translates to more production from partially shaded panels/strings through the elimination of power loss in a sting. For this reason, they are a great option for installations with sun exposure/shading issues such as chimneys or trees shading panels during some of the day or year. They are also a great option for installing on complex roof angles. Micro-inverters can also be installed more quickly than string inverters (because the rapid shutdown system is built in and they don’t require an inverter on your wall). However, because they are a complex piece of electronics mounted in a harsh environment with extreme temperature fluctuations on a daily basis, they therefore experience a higher failure rate than string inverters. Micro-inverters are generally cheaper for small system installations but are not as efficient as newer string inverters with optimizers, which have the same rapid shut down and individual panel monitoring as micro-inverters. For medium to large sized systems, micro-inverters require more circuit breaker space and are best used where electrical service panel space availability is not an issue.
SunPower micro-inverters have a 96% efficiency rating and are slightly more easy to install saving the customer money initially. SunPower micro-inverters coupled with SunPower solar panels produce more energy per day and over the lifetime of the system than any other panel and micro-inverter combination on the market.
SunPower offers a 25 year warranty on their micro-inverters and 10 years on their monitoring systems. The warranty covers labor, shipping costs, and replacements for 25 years, and does not require original receipts/proof of purchase.
SunPower has manufacturing capabilities in both Germany and China, and has been in the solar industry since 1985.
Enphase micro-inverters have a 97% efficiency rating and are also a little bit easier to install, saving customers money initially. However, they have a higher failure rate than SunPower micro-inverters (though newer models may be better).
Enphase has a 25 year warranty on defects in workmanship and materials, and covers repairs/replacements or credits/refunds for the product. The warranty does not cover labor costs, but does cover shipping. Though this is what Enphase’s 2018 policy states, we have had customers experience Enphase not honoring this warranty for inverters installed 10 years ago. Enphase now claims customers need 2 inverters to fail for them to send replacements.
Enphase micro-inverters are designed in California, and are assembled in China and Mexico. The company was founded in 2006.
Battery Based Inverters
OutBack inverters have historically been made for off-grid or micro-grid systems, meaning they required batteries to be operational. However, Outback has just launched a new line of inverters called “Skybox” which will operate interactively with the grid without batteries (batteries can be added later at any time). Outback inverters generally have a lower efficiency rating than other manufacturers (92.5- 94%) and feature a multiple part shutdown system (on your roof & wall). They are American made. OutBack has 30 years of engineering experience and 15 years experience making inverters.
OutBack has a 5 year warranty (with a 10 year extension option) on materials and workmanship. This warranty includes repairs/replacements but does not include labor or shipping costs.