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What's a solar inverter? The solar equipment you need to know

You can't use solar power without an inverter. Here's what you need to know when you're shopping.

A solar installer connects a panel to a microinverter.
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If you're thinking about sticking solar panels on your roof, you might be thinking of doing it soon. The federal tax credit for solar is set to drop from 26% to 22% at the end of this year, and an extension is difficult to predict at this point. In many circumstances buying rooftop solar makes long-term financial sense.

At the same time, the idea of navigating a solar purchase might be overwhelming. It's not something you buy regularly (you might buy it only once in your lifetime) and, while it's becoming more common, it's not quite mainstream. Making an informed decision is your best shot at making sure going solar is not only painless, but beneficial to your bottom line.

A solar inverter is essential to any solar power system. Your system literally won't work without it. Getting the right one can also have a big impact on your system's performance. Ensuring you're being sold a good inverter can make sure you're getting the best system for your house.

What does an inverter do?

An inverter's main function is changing the electricity from direct current to alternating current. Solar panels generate direct current electricity, which can't be used by the grid. An inverter ensures the power you generate is compatible with the grid by switching it to alternating current.

Inverters today do a lot more, though. They're the bit of equipment that monitors and reports power generation and usage. If a solar panel system offers monitoring online or through an app (it likely will), the inverters are collecting and sharing that information.

Advanced solar inverters can disconnect your home from the grid in case of a power outage. Solar arrays without storage and a capable inverter will shut down when the grid goes down, but with the right technology, you can keep the lights on.

What are the different types of inverter?

Inverters come in two types: string inverters and microinverters.

String inverters are the old guard of solar inverters. They do the direct to alternating current conversion for a group of solar panels (or a string, if you want to stick with the jargon) at one, centralized location. They're the cheapest option and, since they're usually installed somewhere easily accessible (like the side of your house), they'll be easier to service if they need it.

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The downside of string inverters is that they're a bit of a blunter tool than their microinverter counterparts. Because they handle whole groups of panels at once, a dip in production in one panel brings down the performance of all the panels. If one of the panels in a string is shaded and produces less power, every panel in the string produces at that lower level. A roof that's partially shaded throughout the day might be better suited to microinverters.

Microinverters perform the same direct current to alternating current switch, but at each individual panel. With microinverters at each panel, the production of panels aren't chained to each other. If one is shaded, another in full sun can keep producing at full-sun levels. Microinverters are more expensive, but better fits for partially shaded or complex roofs where panels face different directions or are set at different angles.

Because microinverters are connected to each panel, servicing them requires a technician getting up on the roof. That means maintenance can be a bit more expensive, though maintenance for solar panel systems is usually fairly minimal. Microinverters typically come with stronger, 25-year warranties, than string inverters, which are typically about 12 years.

A solar panel system might also use a string inverter with power optimizers. Power optimizers don't convert the electricity to alternating current. That still happens in one place at the string inverter. Instead, power optimizers make it possible for panels to produce independently of each other. If one is shaded, the others can carry on. More or less, power optimizers and microinverters accomplish the same job in different ways.

Choosing the best inverter

Once you know whether a string inverter or microinverters are most suitable for your house, you want to make sure you're getting a good product. Within each category, there are a couple of useful points of comparison: warranty and efficiency.

While typical microinverter warranties are twice as long as the typical string inverter warranty, differences exist between products of the same group. A longer warranty might make one inverter a much better choice than another.

Efficiency is a measure of how much energy is lost (usually through heat) as the inverter does its job. Efficiency ratings should be readily available for any inverter on the market. Higher efficiency means less energy lost between the panels and your house.

Like a lot of things in 2022, you might be limited by supply. Supply chain issues have come to the solar industry as well and your preferred equipment might not be available, but it can't hurt to ask. Going in armed with information will ensure you're getting the best deal available.