SolarEdge Inverter Efficiency

[Dawnweaver]

Maximizing the efficiency and longevity of the inverter seem to be worthwhile goals. Running an inverter below capacity may prolong the lifespan of the inverter. But the question is how does this affect efficiency. Conventional wisdom seems to be that the efficiency is maximized near the rated capacity. Looking at the actual efficiency curves, however, efficiency actually goes up as load goes down for some inverters, with a peak efficiency at some point in the middle of the range. For the SolarEdge 3-phase inverters, the peak efficiency seems to be at approximately 50% of rated capacity. For some SunnyBoy inverters, the peak efficiency seems to be even lower. For example, see this efficiency curve for the SunnyBoy 10000TL-US, where the peak efficiency seems to be at approximately 25% of capacity:

sunny_boy-sb8000tlus-sb10000tlus-efficiency-curve (jpeg).jpg

I am not able to find the efficiency curves for the SolarEdge single phase inverters, however. For example, the SE10000A-US or SE7600A-US.

Does anyone know where to find the efficiency curves for the SolarEdge single phase inverters? Alternatively, do you happen to know the load at which peak efficiency is reached?

[dougnet]

I was looking for the same information on the SolarEdge single phase inverters. I just found this PDF file on the SolarEdge web site:

http://www.solaredge.com/sites/default/files/application_note_solaredge_inverters_efficiency.pdf

Hopefully this will help someone. They seem to reach maximum efficiency around 50% load, but stay relatively flat at that point.

[thejumpingsheep]

We are talking about a 1% to 2% efficiency drop... a quick calculation will show that the difference is fairly small.

10kw * 6 (sun hours) * 365 days * .98 = 21,462 kwh per year
10kw * 6 (sun hours) * 365 days * .96 = 21,024 kwh per year

Thats about 440 kwh per year which is probably not a big deal... but in order to do this at max efficiency, you will need a much larger inverter. This can be reasonable to do if you have a very small system (say 2kw), but in my example (10kw), the cost would be significantly higher since you will likely need 4 10kw inverters to max efficiency. They dont make a 40-50kw inverter at low prices. Also, I think youre probably better off simply adding an extra panel and saving money on the inverter than buying a bigger inverter using the same panels.

Adding a single 200w panel to a 2kw system means 10% more power which is waaaaay better than 2% more efficiency.

That said, you might have a point about longevity but I am not 100% sure it will matter in 10 years when the price is cut in half and you can get micro inverters at Walmart for $15-$20. The argument reminds me of folks who used to invest in insane cooling systems for their CPU's back in the early 2000's. They would spend an extra $70 to protect an item that they can replace with a CPU that is double the speed for the same $70 just 2 years later. These inverters will likely be a relic in 5 years due to production scale which is still ramping up.

Again I am no expert.

[Eleceng1979]

Originally posted by sensij View Post
I would suggest ignoring what eleceng1979 wrote in the post above this one... lots of misinformation in there.

[sensij]

You can find test results for inverters here:

http://www.gosolarcalifornia.ca.gov/equipment/inverter_tests/summaries/

Keep in mind that a typical array will not "max out" for very much of the day. Looking at a 10 kW curve and saying a 5 kW array is most efficient because 50% is the peak of the efficiency curve is incorrect. The part of the curve that matters is the steep dropoff in efficiency below 20%. The more you oversize the inverter, the more of each day your system will spend in that low efficiency zone.