A solar installer connects a panel to a microinverter.
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If you’re thinking about gluing solar panels to your roof, you might be thinking about doing it soon. The federal tax credit for solar power is set to fall from 26% to 22% by the end of this year, and an extension is currently difficult to predict. In many cases, the purchase of a solar system on the roof makes financial sense in the long term.
At the same time, the idea of controlling a solar purchase could be overwhelming. It’s not something you buy on a regular basis (perhaps you only buy it once in your lifetime), and while it’s becoming more common, it’s not entirely mainstream. Making an informed decision is your best shot at ensuring that switching to solar energy is not only painless, but positively impacts your bottom line.
A solar inverter is essential for any solar power system. Your system literally won’t work without them. Choosing the right one can also have a huge impact on your system’s performance. Ensuring that you are sold a good inverter can help ensure you are getting the best system for your home.
What does an inverter do?
The main function of an inverter is to convert electricity from direct current to alternating current. Solar panels generate direct current that cannot be used by the grid. An inverter ensures the grid compatibility of the electricity you generate by switching to alternating current.
Today, however, inverters do much more than that. They are the piece of equipment that monitors and reports power generation and usage. When a solar panel system offers monitoring online or via an app (which it probably does), the inverters collect and share that information.
Advanced solar inverters can disconnect your home from the grid in the event of a power outage. Solar arrays without storage and a powerful inverter shut down when the grid goes out, but with the right technology, you can keep the lights on.
What types of inverters are there?
There are two types of inverters: string inverters and micro-inverters.
String inverters are the old guard of solar inverters. They perform the DC to AC conversion for a group of solar panels (or a string, if you want to stick to the jargon) in one central location. They are the cheapest option and since they are usually installed in an easily accessible location (e.g. on the side of your house) they are easier to service when needed.
Look at that:
Lucy’s gigantic solar panels unfold during the test
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The downside to string inverters is that they’re a slightly more blunt tool than their microinverter counterparts. Because they process entire groups of panels at once, a drop in production in one panel lowers the performance of all panels. If one of the panels in a chain is shaded and producing less power, each panel in the chain will produce at that lower level. A roof that is partially shaded throughout the day may be a better fit for microinverters.
Microinverters perform the same DC-to-AC switching, but on each individual panel. With micro-inverters on each panel, panel production is not chained together. If one is shaded, another in full sun can continue to produce in full sun. Microinverters are more expensive but are better suited to partially shaded or complex roofs where the panels face different directions or are at different angles.
Because microinverters are connected to each panel, maintaining them requires a technician to climb to the roof. This means that maintenance can be a bit more expensive, although maintenance for solar panel systems is usually pretty low. Microinverters typically have a stronger 25-year warranty than string inverters, which are typically around 12 years.
A solar panel system can also use a string inverter with power optimizers. Power optimizers do not convert the current to AC. This still happens at one point on the string inverter. Instead, power optimizers allow modules to produce independently. If one is shadowed, the others can move on. More or less, power optimizers and microinverters accomplish the same task in different ways.
Choosing the best inverter
When you are deciding whether a string inverter or microinverter is best for your home, you want to be sure you are getting a good product. Within each category there are a few useful points of comparison: warranty and efficiency.
While typical microinverter warranties are twice as long as the typical string inverter warranties, there are differences between products in the same group. A longer warranty can make one inverter a much better choice than another.
Efficiency is a measure of how much energy (usually to heat) is lost while the inverter is doing its job. Efficiency values should be readily available for any inverter on the market. Higher efficiency means less energy loss between the panels and your home.
As with many things in 2022, you might be limited by supply. Supply chain issues have also arisen in the solar industry and your preferred equipment may not be available, but there’s no harm in asking. If you’re armed with information, make sure you get the best deal available.
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