A big question for homeowners when deciding to go solar is whether to choose a micro inverter or a string inverter. The answer for what is best for you really depends on the specifics of your project. To cover the basics, the function of an inverter is to convert the direct current your solar panels produce into alternating current so that you can use it in your home.
A string inverter functions in a series circuit, while a micro inverter functions in a parallel circuit. Simply put, a string inverter will cap the electricity production of each panel by the lowest producing panel on your roof. A micro-inverter, on the other hand, will take full advantage of the production of each individual panel. Therefore the functionality of a micro-inverter does outperform a standard inverter, but is it worth the extra cost?
That answer lies in the layout of your solar system. If a solar system is facing multiple angles, meaning some panels are facing south, some east, and some west, then micro-inverters are the way to go. Or, if you have shading issues from trees or a large chimney, again, micro-inverters would be best. In these situations, the solar panels will be producing different amounts of electricity at different times of the day, but micro-inverters will ensure you harvest all of the energy, while with a string inverter you will lose some of this production. With solar panels all facing one direction on your system, and you have marginal shading issues, then your best option is a string inverter. You’ll get about the same production, without paying the higher cost.
To throw more confusion in this, optimizers are an option for string inverters as well, which function very similarly to micro-inverters. With an optimizer, you still have a string inverter, but you also have optimizers for each individual panel combating production differences. The cost of optimizers fall in between that of micro and string costs.
Micro-inverters and the add-on optimizers both offer an additional perk in system monitoring as well. With either of these devices, you have the ability to track the production of each individual panel, while with a standard inverter you only can track the production of the whole system. If you were to expand your system in the future, micro-inverters are simple to add one at a time. However, with a string inverter, it would be more costly to add another full unit.
To sum it all up, micro-inverters are definitely a value-add, but are only recommended if you have panels facing multiple orientations or you have shading issues. Otherwise, the less expensive string inverter is the way to go.