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AC Micro inverter vs DC string inverters

A big question for home owner when deciding to go solar whether to choose micro inverters or string inverters? The answer for what is best for you really depends on the specifics of the solar project. To cover the basics the function of the inverter is to convert the direct current your solar panels produce into alternating current so that you can use the electricity in your home.

A string inverter functions in a series circuit while the AC micro-inverter functions in a parallel circuit. Simply put a standard string inverter will cap the electricity production of each panel by the lowest producing panel on your roof. A solar micro inverter on the other hand will take full advantage of the production of each individual panel. Therefore, the functionality of the AC micro inverter does outperform the string inverter in certain circumstances, but is it worth the extra cost?

If you have limited roof space and you are forced to have your solar system facing multiple angles, say some panels are facing north, some east and some west then solar micro inverters are the way to go. Also, if you have shading issues from trees or a large chimney again micro inverter will be best. In these situations, the solar panels will be producing different amounts of electricity at different times of the day, but AC micro inverters will ensure that you harvest all that energy.

While with string inverter will lose some of this production. If you have a solar system where all of the panels face the same direction and have no shading issues, then your best bet is string inverters. You will essential get the same production without paying the higher costs.

Optimisers are an option for string inverters as well. Optimisers function very similarly to microinverter with an optimiser you’ll still have your string inverter, but you’ll have optimisers for each individual panel combating the production differences. The cost of optimisers falls in-between that of the micro-inverter system and then string inverter system.

Explaining the Enphase AC Micro Inverter

At Watters we regularly use an Enphase AC micro inverter solution when we have clients who have shading issues. The mini inverters we commonly use are the Enphase S270 Microinverter pared with the Enphase Envoy-S Metered Communications Gateway. The Enphase Envoy-S Metered Communications Gateway is the brains of the AC system. It communicates with each micro inverter and your monitoring system.

When sizing an AC solar system each Enphase S270 Microinverter is a total of 270 Watts of output per micro inverter. So, a 15 panel AC solar system will have a total of 4kW’s of total inverter output. Paired with 330-Watt solar panels will have a total wattage of 4.95kW’s output. This is something to understand when considering an AC solar solution.

SolarEdge power optimizer

SolarEdge power optimizers offer a product for DC solar systems to have similar features and benefits to an AC micro inverter. Whereas each solar panel works as an individual solar system, and not effected by the performance of other panels. The monitoring available on the SolarEdge is also like the Micro Inverter with the ability to track the production of each individual panel.

Micro-inverters and optimisers also offer an additional perk in system monitoring as well. With both devices you’ll have the ability to track the production of each individual panel, but with a standard inverter you can only track the production of the entire system.

If you would like to expand the system in the future Micro inverters are simple to add-on one at a time. However, with string inverters it would cost more to add another full unit.

To sum it all up, micro inverters are definitely a value add but are only recommended if you have shading issues otherwise the less expensive string inverter is the way to go.

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