What is a solar inverter and what is it for?

A solar inverter is one of the most crucial parts of a solar power system. A solar inverter converts the power output of solar panels into usable electricity for the area where the installation is made. In this post we explain how a solar inverter is installed on the solar panels.

A solar inverter works by taking variable direct current, or DC output, from your solar panels and transforming it into 120V/240V alternating current (AC), or AC output . Appliances in homes run on AC, not DC, so the solar inverter must adapt the energy captured by the solar panels to be used by those appliances.

The inverter takes power and passes it through a transformer, which is then injected into the alternating current (AC) output. Actually, the inverter “fools” the transformer into thinking that direct current is actually alternating current, by forcing it to act in a similar way to alternating current. The inverter runs direct current through two or more transistors that turn fast on and off and feed the two variable sides of the transformer .

Currently, there are 5 types of solar inverters, all of them with different benefits.

1.- Battery inverters 

A battery inverter is the best option if you need to retrospectively install a battery for the solar system, or if you want to keep the battery separate from the solar panels and run it through a different inverter. A battery inverter converts battery power to 230V and alternating current (AC) and feeds it to your distribution board (instead of the mains) whenever possible.

2- Central investors

A central inverter is a huge piece of equipment and is typically used for systems that require hundreds of kilowatts (or sometimes even megawatts) of volume. They are not for residential use and resemble a large metal cabinet, where each “cabinet” can handle around 500 kW of power. It is typically used commercially for large-scale installations or large solar farms.

3.- Hybrid Inverters

Hybrid inverters, also known as “multimode inverters” allow batteries to be connected to a solar installation. It connects to the batteries through “DC coupling” (when both solar power and batteries use an inverter and DC power from the solar panels charges the batteries via a DC charger) and its electronics organize the charging and discharging of the battery.

4.- Micro-inverters

Microinverters are relatively small, to give us an idea, they are the size of a book. The ratio of solar panel to microinverters is 1:1. The main benefit of a microinverter, among others, is that they optimize each solar panel individually, offering more power, especially in shady conditions.

5.- String inverters

Lastly, there are string inverters. String inverters are the most common inverter option for residential use, and there is typically 1 string inverter per solar installation. They are labeled “String Inverters” due to the fact that they connect to a string of panels.

The size of the inverters will depend on the power we want to install. For example, if we have a 3 kW system, 3 kW panels and a 3 kW solar inverter will be needed. However, there are exceptions to this proportional rule depending on the system, the technology used and other factors, but for pre-sizing it is usually valid.