What About Micro Inverters?

In recent times micro inverters have become more popular. How do they work and whats the difference between them and traditional inverters? What are the pros and cons of using micro inverters? And most importantly are they right for you? These questions are answered below.

How do they work?

Traditional (string) inverters require panels to be electrically linked together in what's called a string (like a chain). Depending on the size of the system you can have one or more strings usually comprising of a minimum of six or so panels, but often quite a few more. Wiring is then taken back from the string of panels to the inverter, usually located near the switchboard. The inverter then works out the optimal operating point for the entire string.

Micro inverters are mini inverters that are usually placed under the panels (see accompanying picture). One micro inverter is used for each panel (or with some brands one for two panels). Each micro inverter then works out the optimal operating point for each panel. It thus gives more accurate, independent control of each solar panel.

What are the pros and cons of micro inverters?

There are several pros for top quality micro inverters. They include:

  • Longer life expectancy than string inverters.

  • More flexibility in designing systems - particularly valuable if you have several roof sections with limited space. While with traditional inverters you need a minimum number of panels together facing the same direction, with micros you can have any number you want - even one on its own.

  • Can easily add more panels later.

  • Much less affected by shading. With string inverters if one panel is shaded then all the panels in the string are affected. With micro inverters, only panels that are actually shaded are affected.

  • Come with online and remote monitoring as standard.

  • Allow you to monitor your electricity consumption as well as your solar production.

  • Allow you tell if any individual panels aren't working.

  • Higher safety as high DC voltages are avoided.

What are the cons? Firstly some of the cheaper micro inverters have had a high failure rate. For this reason we recommend using only top quality premium micro inverters. Also, as there are more components, there is more chance of something going wrong - and some of the warranties only cover the component - which means you would be up for the labour cost to replace faulty components. At least however, if one micro inverter fails, the rest of the system will keep working.

The other con is the price. Using premium micro inverters usually works out considerably more expensive than string inverters. That leads us to the final question. -

Are micro inverters right for me?

The biggest of the advantages of micro inverters is that they can provide better production in partly shaded conditions. So, where shading is a problem then micro inverters can be a good option.

However, optimizers are now also available (these are also fitted behind the panel but work with a normal string inverter). These provide at least as good mitigation of partially shaded conditions and usually work out much cheaper as you can use them selectively rather than on the whole system . In shaded conditions we strongly recommend using either optimizers or micro inverters

Where shading is not a factor, then it comes down to preference and budget. If some of the other features of micro inverters appeal to you, and its within your budget, then you may prefer micro inverters. Otherwise there are lots of good choices in string inverters.