The inverter is at the heart of a residential solar power system. It is an electronic device that converts direct current (DC) electricity into alternating current (AC) electricity which is used in your house. DC power is what you get from solar panels, and also what you have from any battery. In addition to changing the type of electricity from DC to AC, the inverter takes care of changing the voltage from the low (12+) volts up to the 110 volts of the mains power system.

Depending on the arrangement of your solar power system, you may have batteries to store the solar energy from the panels. In this case, the inverter is used from the batteries to provide the power to your house circuits. If you do not have batteries, but are tied directly to the utility grid, the inverter still changes the voltage, this time direct from the solar collectors, into the house and grid system.


Photo: by John Kasawa

Inverters are available in various sizes, depending on the power required. You may be familiar with the type of inverter that you can buy at a truck stop, which plugs into the outlet in your car, and allows you to run mains power equipment in your car. Of course, the power of your car is not enough to power your house, and the inverter will typically only power one or two receptacles, at 15 amps. Nonetheless, it will have a cooling fan as the action of changing the electricity generates a lot of heat, and it will have a cutout to stop it functioning if too much load is put on the receptacles.

The inverter which you have for your solar power system is, of course, much larger. It will need to be in an open space, and will be expected to get hot, depending on the load put on it. It is the one component of your system which cannot be easily upgraded to a higher duty – more batteries can be added easily for more power storage, more solar panels can be added easily for more power production, but you will need to replace your inverter with a larger unit if you decide to start small and gradually upgrade the size of your solar power system.

It’s best to keep the inverter fairly close to the DC power source. The AC wires can be run further if necessary. Incidentally, that’s why mains power is AC, not DC, as it’s easier to run it long distances.

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