What is a solar inverter? How does a solar inverter work?

Solar panels aren’t the only component that you should be thinking about when you evaluate your solar system equipment. Solar power inverters play an equally important role in a solar system: they convert the electricity your solar panels create into a form that can be used by the appliances, lighting, and other electronics that are in your home. Once you understand how solar inverters work, and the different types of inverters available for solar.

What does a solar inverter do? How solar inverters work in a PV system

When the sun shines on your solar photovoltaic (PV) system, electrons within the solar cells start to move around, which produces direct current (DC) energy. Circuits within the cells collect that energy for you to use in your home.

This is where your solar inverter comes in. Most homes use alternating current (AC) energy, not DC, so the energy produced by your solar panels isn’t useful on its own. When your solar panels collect sunlight and turn it into energy, it gets sent to the inverter, which takes the DC energy and turns it into AC energy. At that point, your solar electricity can power your appliances and electronics or, if you’re producing more electricity than you need, it can feed back into the grid.

Comparing solar inverter technologies: string inverter vs. string inverters with power optimizers vs. microinverters

All inverters have the same basic task: convert DC solar energy into useful AC energy for your home. However, there are three different solar inverter technologies that you can choose for your solar panel system, and each of them works slightly differently.

String inverters: a standard centralized inverter

Most small-scale solar energy systems use a string inverter, also known as a “central” inverter. In a solar PV system with a string inverter, each panel is wired together into a “string”, and multiple strings (normally up to three) can be connected to your central inverter. When your panels produce energy, it all gets sent to a single inverter, which is usually located on the side of your home, in a garage, or in your basement. The inverter will convert all of the electricity from your solar panels into AC electricity for use on your property.

Pros: String inverters are the lowest-cost inverter option, and are a very durable inverter technology. They are also the easiest to maintain, because they are in an easy-to-access location.

Cons: A drop in the performance of an individual solar panel (i.e., from shading) can impact the output of all of the panels on an individual string. While multiple strings can accommodate multiple roof planes on the same inverter, string inverters may not be right for more complex system designs or roofs with regular shading.

Best for: Properties with “uncomplicated” roofs that get consistent sun throughout the day, and homeowners looking for lower-cost solar PV systems.

Power optimizers: a panel-located option to pair with a string inverter

Power optimizers can be thought of as a compromise between string inverters and microinverters. Like microinverters, power optimizers are located on the roof next to (or integrated with) individual solar panels. However, systems with power optimizers still send energy to a centralized inverter.

Power optimizers don’t convert the DC electricity into AC electricity at the site of the solar panel. Rather, they “condition” the DC electricity by fixing the voltage of the electricity, at which point the electricity is sent down to the string inverter. A system that pairs power optimizers with a string inverter is more efficient than one that uses a string inverter alone in shading scenarios.

Pros: Like microinverters, power optimizers can improve the efficiency of your solar panel system if you have a complicated roof or frequent shading; however, optimizers tend to cost less than microinverters. They optimize the output of each individual panel to mitigate the impact any one shaded panel can have, and also provide the benefit of monitoring the performance of individual panels.

Cons: A system that pairs power optimizers with a string inverter will cost more than a system with a standard string inverter option. As with microinverters, solar PV systems that include power optimizers can be more difficult to maintain.

Best for: Homeowners with a slightly less than ideal roof for solar who are willing to pay more to increase the performance of their solar panel system, but who don’t want to invest in microinverters.

Microinverters: high-performance at a higher cost

If a string inverter can be considered a “central” inverter, microinverters are “distributed” inverters. Solar PV systems with microinverters have a small inverter installed at the site of each individual solar panel. Rather than sending energy from every panel down to a single inverter, microinverter systems convert the DC solar energy to AC energy right on the roof.

Pros: Having microinverters at every solar panel provides performance benefits, especially for systems with a more complicated design or that experience shading. Microinverters optimize the output of every panel at the panel to mitigate the impact of shading, and to allow for panel-level monitoring of your system.

Cons: Microinverters cost significantly more than a string inverter, and can be more difficult to maintain or repair in the event of a problem because they are located on the roof.

Best for: Systems with solar panels that face multiple directions, homeowners who want to maximize solar production in a small space, and properties that have “complicated” roofs with gables, chimneys, or other objects that can cause shade.

Choosing the best inverter option for your home

Now that you understand how solar inverters work, your next step is to decide which type is best for your solar PV system. Not every system-design is right for string inverters, and it’s not always necessary to pay extra for optimizers or microinverters. Ultimately, there’s no universal right or wrong answer, only what’s best for your own situation and needs.

While you can continue to read about the different technologies, the best way to find out which option works for you is to review actual quotes from qualified local installers in your area.