View the thread, titled "size of inverter on a 2.9kw pv system" which is posted in Solar PV Forum | Solar Panels Forum on Electricians Forums.

i`ve just had a 2.94kw solar pv fitted and the inverter is a sunnyboy 2500hf(2.5kw) which means i`ll never get more than 2.5kw output i understand efficiency of the system x.8 etc which brings it under 2.5kw if i had a 3kw inverter would i on a sunny day acheive more than 2.5kw if so why do you think the fitting company choose the smaller inverter
 
The key is that the inverter will be more efficient at lower power. Your 2.94kWp system will only produce that figure every now and then - while it will be around 2-2.5kWp most of the time. The installer, in my opinion, fitted about the right size (bearing in mind I have no idea what panels have been used)
 
Inveters are also designed to be 'overated' because they are unlikely to produce the maximum power very often, 25% over-rating is usually just fine even on a South facing roof @ 37 degrees.

The panels, location, orientation and inclination will have an influence on any one specific installation.
 
I had a similar question - we have a 12 panel Sanyo HIT 240W HDE4 = 2.88kwh systemo on a Sunny Boy 2500. Despite the beautiful weather we had during May the max we got was 2.562. We also have a problem that the inverter is reading 9kwh higher than the generation meter (the one we get paid by) against a total generation of 532 since May 4th. Can anyone tell me if this seems right?
 
You setup looks OK (from this distance). If you are familiar enough with the terminology then you can download Sunny Design yourself and try out your set up to see whether SMA think it is a good match. It will be. A SB 2500 would not be expected to output more than ......... 2500W.

Your total generation meter has to be calibrated to a particular standard whereas the one in the inverter does not. So a percent or 2 difference is not unreasonable. Bear in mind also that the total generation meter will not be measuring any power lost in the cable between the inverter and the total generation meter. If that is any length it could account for say 1%.

Regards
Bruce
 
Thanks for that I have looked at the SMA site. Obviously the SMA site only deals with the SMA Range so will produce the best fit from their availability and will not tell you whether another make of inverter would be a better match. It just seemed a bit strange to put an inverter on that will never allow the system to generate to its full capacity.

You setup looks OK (from this distance). If you are familiar enough with the terminology then you can download Sunny Design yourself and try out your set up to see whether SMA think it is a good match. It will be. A SB 2500 would not be expected to output more than ......... 2500W.

Your total generation meter has to be calibrated to a particular standard whereas the one in the inverter does not. So a percent or 2 difference is not unreasonable. Bear in mind also that the total generation meter will not be measuring any power lost in the cable between the inverter and the total generation meter. If that is any length it could account for say 1%.

Regards
Bruce
 
Thanks for that I have looked at the SMA site. Obviously the SMA site only deals with the SMA Range so will produce the best fit from their availability and will not tell you whether another make of inverter would be a better match. It just seemed a bit strange to put an inverter on that will never allow the system to generate to its full capacity.

Yes, I thought that at first sight many months ago. But if you look at some of the technical papers on the subject, the inverter spends much more of its time generating at say half power than it does at full power. Slightly undersizing it means it works more efficiently at the half power times because of the relatively higher voltages. Overall, more is gained there than lost at maximum power. This is reflected in the SMA model (and others) if you play with it.

Different inverter makes might do slightly better (or worse), but they cannot make something out of nothing - laws of physics apply. You are likely to be dealing with very small differences and where do you think that you can get independent performance data you can trust? More significant I suspect is the technology you choose: ordinary transformer, hf transformer or transformerless; and how recently designed.

Regards
Bruce
 

Reply to the thread, titled "size of inverter on a 2.9kw pv system" which is posted in Solar PV Forum | Solar Panels Forum on Electricians Forums.

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