Shade



The conventional wisdom is that you need micro-inverters or DC optimisers fitted to your solar panels to combat shading.

"If one panel fails or gets shaded then all the panels on that string will be dragged down"

Sound familiar? It should do because for many years we and everyone else in the solar industry (and therefore all our customers) believed it to be true.


The truth though, is that in almost all cases the technology within the solar panels and inverter (if it's a good inverter) will get the job done without optimisers or micros.

Inverters that we know for sure that have the all important 'Global Maximum Tracking' feature are Fronius, SMA, and Huawei.

SMA dumbed it down for us and called it 'ShadeFix' but the feature is the same with all these good quality inverters and it is entirely probable that most other brands of inverter have this feature as well, because, to be frank, everyone copies a good idea in the solar industry.

The inverter capability, coupled with the diodes inside panels and the way that the cells inside 'half-cell' panels are strung together means that it is unlikely that you would ever need to install micros or optimisers to combat shade.

Whaaat?

If you are new to solar then you'll not be too bothered by the above information, but if you have already spent many thousands of dollars extra on micros or optimisers to combat shade, you are most likely reading this feeling a bit peeved.



Having written all that, I must put in a good word for micros and optimisers.

They usually DO combat shade better than a quality string inverter. Not always, but usually.
The more severe the shade the worse micros perform compared to string inverters because the defense mechanism of the solar panels (diodes) isn't always activated.
Micros can cause the bypass diodes in the panels to be bypassed which isn't a good thing.

Most of the various real World comparitive tests show a 1 to 3% advantage in various shading situations in favour of micros and optimisers. The big question is whether that small advantage can be cost-justified. In my experience it usually can't, but many people still go ahead and 'optimise' anyway.

I think Eddy May from NRG Solar has put together a good video showing a test between a good string inverter (in his case Fronius) and Enphase micros in his Adelaide business car park.

If you are a bit more technically minded, Mark at MC Electrical in QLD explains WHY in his video(s) but I recommend you watch Eddy's video first.

The cost for a Huawei, Tigo or SolarEdge optimiser is about $90. Enphase micros are about $180 each. The micros cost double because they contain electronics to do another job...converting the DC electricity from the solar panel to AC right there on your roof, not down at the ground inside a central 'string' inverter.

We install quite a lot of DC optimisers, mostly Huawei with the Huawei inverters. Sometimes we DO optimise strings where some of the panels get shading, even though as described above, it's not strictly necessary, but at least we all then have PROOF that the shade isn't hurting the system because with Huawei, once a panel has an optimiser fitted, the individual output of the optimised panel shows up in the reports.

Enphase, via their 'Envoy' monitoring box have this panel level reporting feature for their micros, as do some, but not all of the SolarEdge products (Genesis inverter, no, Energy Hub and three phase hybrids, yes). Tigo optimisers, which can be fitted to panels connected to any string inverter also have this feature if you also buy the optional control box.

There are other benefits with optimisers and micros that go beyond shading and panel level reporting. Safety is one (e.g. arc fault detection), and another is the ability to manipulate string voltages to create 'super long strings' and 200% and sometimes even more, inverter oversizing when a battery is connected, but the most common reason is to allow panels to be fitted anywhere, any orientation North, West, East, South and all points in-between in any quantity, and at any tilt.


Solar4Ever have been selling and installing solar in Perth, WA since 2011.

(08) 6102 2527


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This review was written by Andrew MacKeith, Solar4Ever service manager since 2011.
Most recent update April 2021