Central inverter or micro-inverter: Which is right for me?

Central inverter or micro-inverter: Which is right for me?

Central inverter

Example of a central inverter installed on a rooftop solar system.

A solar photovoltaic (PV) system is just that, a system. There are several components that are needed to convert the sun’s energy into electricity to help you save money on your electricity bill. One key component in the system is an inverter. Inverters convert direct current (DC) electricity produced by your panels into alternating current (AC) so it can be used by your home or business electric devices.

To understand the process, a quick refresher on how solar panels convert sunlight to electricity is necessary. Photons from the sun hit electrons in solar panels. This interaction creates direct current. Your home and appliances use alternating current. So, an inverter is needed to ensure the DC electricity generated by your panels is turned into usable AC by your home.

There are two types of inverters: central inverters and micro-inverters.

Central inverters receive all of the energy generated by multiple panels and convert it to alternating current in one central location. Central inverters are usually located at ground level near the main electrical service panel, with a wire connection to the panels. Central inverters optimize energy conversion for the entire system. But, shading of one or more panels can bring down the performance of the rest of the system. Technologies such as maximum point power tracking (MPPT) can help to optimize central inverter performance in shaded conditions.

Micro-inverters are smaller inverters connected to each panel and convert DC into AC electricity at the point of the panel itself. So, if one panel is shaded, this shading won’t diminish the production of the other panels. Micro-inverters are also optimized for the production of each panel and can increase power production by 5% to 25% compared to central inverters. All inverters generally have online monitoring options that allow for the tracking and monitoring of whole system production and performance. Micro-inverter monitoring systems give the option for panel-level monitoring allowing showing data on individual panel performance. They also make it easier to add more panels once a system has been installed. Micro-inverters do have limitations. Most micro-inverters cannot accommodate high wattage panels (roughly greater than 285 watts). Micro-inverters may also complicate the process of connecting your system to a battery.

Compared to central inverters, micro-inverters generally (although not always) come at a higher cost. The decision to opt for micro-inverters should be based upon your system’s lifetime expected performance and your estimation of how much improvement you would see from using a micro-inverter.

Broadly, if you are using high-quality panels and have a completely unobstructed roof, you may be financially better off with a central inverter. If you have concerns about the performance of individual panels, or have partial shading, micro-inverters may be a wise investment.

Like any component of your solar system, the ultimate decision on which inverter to choose will be based on your site characteristics, budget and system expectations and goals. A reputable installer will walk you through the advantages and disadvantages of your inverter options.