Solar panel production figures

Agreed, but I was duped by the fancy shpeel on the 2 MPPTs meaning it’ll do 3.6kW ac and 3.6kW dc concurrently. Which is fine if I had 30kWh of battery storage, but the suppliers knew I didn’t.
So by 9am, battery is full and it’s pegged at 3.6kW ac all day.
 
NoNameNoNumber said:
Agreed, but I was duped by the fancy shpeel on the 2 MPPTs meaning it’ll do 3.6kW ac and 3.6kW dc concurrently. Which is fine if I had 30kWh of battery storage, but the suppliers knew I didn’t.
So by 9am, battery is full and it’s pegged at 3.6kW ac all day.
Click to expand...

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.

zJbq1ze.png


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

nGrg1Mc.png


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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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.

zJbq1ze.png


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

nGrg1Mc.png


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! :)
Click to expand...
He's 82% over-panelled though compared to your 57% and only has a 5.2kWh battery. His generation will be skewed towards the afternoon when the battery is already full. Depending on the inverter, he might be maxing out the wattage on the MPPT with the SW facing panels on too. I don't think on the right inverter it's too much to expect 6500kWh (1000kWh more than now) on 6.7kW of panels facing SE and SW. I don't know where he's located, but even here in Yorkshire my 4.8kW SE array made 4767kWh in 2023, which wasn't a great year for sunshine either.
 
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