What is a solar inverter and how is it used?

Technical terms like "solar power inverter" tend to make people's eyes glaze over, but the idea behind this indispensable device is pretty simple. It turns one type of electrical energy into another. And if you have photovoltaic (PV) solar panels on your roof, that conversion is vital to powering your home.

First things first: There are two types of electrical energy – direct current (DC) and alternating current (AC). DC is great for powering smaller items over short distances, like a flashlight. AC travels better, so it's used in powerlines, and it's the stuff that comes out of wall sockets.

So how does a solar inverter work? When sunlight hits a solar panel on the roof, the panel converts that energy to DC electrical energy. But since homes are wired for AC, that DC energy has to be converted to AC. The SunPower solar inverter does that, allowing the energy to power your home. If you use net metering, the inverter also allows the energy to be fed into the electrical grid.

But inverters do more than that. They also provide protection against "ground faults" – basically an exposed or "hot" wire coming in contact with a grounded item. In some ways they're also the brains of a solar system, providing stats on voltage and current, energy production, and tracking maximum power.

For a long time, all home solar systems had one central inverter. Wires from all the solar panels on a roof ran into a big box installed in the garage or on the side of a house. But SunPower solar systems like the SunPower’s Equinox home solar system now rely on microinverters. A microinverter converts the power from DC to AC at the panel level, creating a serious boost in efficiency.

How? With central inverters, all the wires leading to the inverter usually connect the panels together, like lights on a Christmas tree. But just like lights on a Christmas tree, that set-up can go awry thanks to one small problem.

Say there are 24 panels on a roof. If shade covers just one of those panels for a couple of hours a day, the entire string of panels will underperform for those two hours. Though the other panels are producing maximum power, the problems of the one shaded panel will keep much of their energy from passing through the central inverter.

The Equinox system gets around this by putting microinverters under each panel. Each panel is independent, so if shade hits one panel for a couple of hours, then only that one panel is affected. As a result, much more power gets into the home.