Solar panel production figures

DarkBahamut said:
2 MPPTs just means it can track 2 strings of panels independently. Doing 3.6 kW to both AC and DC together is a different thing - though these days inverters tend to have both of those abilities.

I think if you can easily and cheaply get the bigger inverter you probably should, though I don't think you'll get some of the mentioned improvements either. The best day improvement you might see is realistically more like 20-25% IMHO, certainly not 40-50% (and remember "best" days are uncommon, not the norm, either). SE SW split systems end up with a somewhat flat generation curve in the middle of the day, so clipping by 9am sounds like you'd be making tons of power at midday, but in reality, your generation climbs quickly, then stalls and you sit at a lower level than you might otherwise expect. We also have a SE SW split, and by 10am the SE panels are already at their peak, and by 11am power on that MPPT is already starting to fall away noticeably. It does mean you get a nice long useful generation period though - but all this reduces the effects of clipping.

You end up with curves like this. Almost looks like we had clipping, but this is a fully unclipped day. Cloudy start but the PV peak was at 10:05 am then a flat pancake for nearly 3 hours.



That isn't just a once off either. Here's today so far:



Generation at 11:47 was the same as 9:03! (8.33 kW vs 8.34 kW), again no clipping today, just SE SW things :D

We do have more panels SE than SW, so the opposite to your situation, but we do have a similar clipping situation. We have 9.46 kWp on a 6 kW inverter. Less as a ratio, but we are 3.46 kW over our inverters AC rating, a little more over in raw power than you. As we have a large battery I can avoid actually clipping by charging the battery from the "clipped" power only, which also allows us to exactly measure how much power would have been clipped on any given day. Up until midday today that total was 3.8 kWh. So by the time we drop below "clipping" generation power I suspect the total will be 7-8 kWh. So keep that in mind, you might make ~7 kWh more on a sunny day if you avoided clipping. Not to be sniffed at, but I bet that doesn't add 50% to your good generation days! And to make an extra 1000 kWh a year you'd need 143 such days which I don't think is realistic with our UK weather! It's possible the very best days in June will clip even worse, but the vast majority of the days will clip less than this even.



tldr: Bigger inverter good, just keep expectations for gains realistic! :)
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Here's my 3.6kW inverter yesterday
40.2kWh produced.
27.7kWh exported

Looks like heavy clipping to me through the ac export. We use our battery different now too. For the first year we were on a fixed tarif. 28p in/15p out. Now we’re on Agile so I’ve set it to prioritise battery if unit price >16p.
This way we can stay off grid 16-19:00 when unit price is often >30p.

UtQuJ3Ol.jpg


Battery is teal, full from cheap rate grid
Green is PV which reaches peak at 10:10 on the SE side with 7 panels. I think they’re 395w ea.
 
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200sols said:
Looks like a lot of clipping to me, a good 6 hours. You'd have to do some sums and price up inverters and calculate the ROI.
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I'm not paying for the upgrade.
Mercenary Keyboard Warrior said:
For sure you got some clipping but remember the top of the generation is a curve not a peak.

You could if you really wanted to prove it run only one string one day and run the other the next. You would see the potential of each string of panels that way.
Although each string may be capped individually as well (likely) as in total.
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I understand, but neither end of my curve show signs of slowing down. I expect my peak might hit 5kW with ease
 
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