What is a micro inverter?

A micro inverter performs the same function as a regular string inverter, in that it converts DC electricity coming from your solar panel into AC for use in the home, but instead of having one large inverter per 8-16 Solar PV panels, you have one micro inverter per panel. The micro-inverter is physically located on your roof.

A micro-inverter control unit will provide control of all the micro-inverters. This control unit will allow the user to monitor each individual micro inverter and its associated Solar Panel, since the control unit communicates with the manufacturer’s cloud-based monitoring service.

Advantages

Multiple orientations. Perhaps you might want to put solar panels on more than 2 roof orientations. You might have a South, West and East facing roof. To achieve this with a regular string inverter will likely require more than one string inverter to be installed, since most inverters can only accommodate 2 strings. With micro inverters, this problem disappears, since each Solar Panel is treated individually. Therefore the AC output from each micro-inverter can be wired up in series, with the total output routed to the consumer unit as normal.

Small Arrays. This is particularly useful when considering installing smaller Solar PV arrays. With a micro-inverter set up, you can even have just a few solar panels installed on a roof – there is no minimum viable size of array.

Fault finding. Since each panel is being monitored individually, it is easy to identify whether any individual panel is suffering a problem. With a string inverter, this isn’t possible, and there will be some detective work required to figure out where the problem is.

No Single Point of Failure. This all adds up to mean that there is no single point of failure. If a regular string inverter fails, it must be repaired or replaced, or whole array will suffer an outage. If on the other hand a micro-inverter or solar panel fails in a micro-inverter set up, then only that one element ceases to function, and it doesn’t affect the functioning of anything else.

Warranty period. The warranties associated with micro-inverters are longer, and can be up to 25 years – the same length of time as the solar panels themselves in fact. This is because the work that each micro-inverter is having to do is significantly less, meaning it is under less strain.

Optimising. The micro-inverters act as an optimiser, which means that it can help to limit the effect of shading on the power output of the solar panel under some circumstances. If the power output of part of the array is limited (whether by shading or by dirt on the panels) by having micro-inverters each panel will function at its own optimum capacity, whereas with a string inverter, the whole array will be limited, and only function at the capacity dictated by the worst performing panel.

Disadvantages

Cost of installation. At a rate of one inverter per Solar Panel, the cost of installing micro-inverters is inevitably higher since 16 micro-inverters cost more than one string inverter.

Cost of replacement. Whilst the micro-inverters might last longer than a regular string inverter, it they do malfunction, then a tradesperson will need to access your roof, since the micro-inverter is attached underneath your solar panel. If this involves scaffolding, then the cost of replacement will be significant – and likely more than replacing your string inverter at the end of its lifespan.

Conclusion

Currently the ‘Industry Standard’ is to use a string inverter. This might be a regular sting inverter, or a hybrid inverter if considering installing batteries alongside the solar.

Installers are usually comfortable installing what they know and what they have direct experience of. And there is much to be said for this.

As to whether the smart decision is to install a string inverter or a micro inverter, this is unfortunately not that straight forward. One key advantage of Solar Panels over other technologies is that they require virtually no maintenance (other than occasional cleaning, perhaps). The string inverter will likely need to be replaced once during the life of the Solar Panels – but this is an easy and quick job for an electrician, and therefore inexpensive to complete.

Failure rates on micro-inverters are reported to be very low, hence why the manufacturers can offer such long warranties. However, if it does require replacing, since it is up on your roof, any replacement will likely be a difficult and expensive job. If scaffolding is required to access your roof, then the costs will be dramatically higher than for a single story roof without scaffolding costs.

Like anything in life, there are pros and cons to each decision.

At Brimstone Energy, we’re here with you every step of the way, as we enter the Green Energy Revolution.

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