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Posted a thread earlier this year giving a comparison of total outputs of a friends 4kW system to that of mine. We are located within 200yds of each other in north Essex. He has 10 Suntech 250W panels, 8 facing due east the othe 8 due west connected to a SMA 4000TL Inverter. Mine 16 Hyundai 250W panels all face due west again connected to a SMA 4000TL (2 strings of eight)
Friends system operational for a week longer than mine, but both fitted last November. Generation meter readings as of last Friday 27th July. Friends - 2017 KwH. Mine - 2303 KwH.

The figures taken earlier in the year favoured myself by some 100 plus Kw but we thought that the summer (if you can call it that) might start to normalise the readings to similar amounts, but it differnce now increased to 286 KwH.

Could it be down to Inverter mismatch on the east west split or is it best to have all panels to one aspect, east or west?

Welcome your comments on similar experiences.



There may be other factors why they are different, personally I would have used a smaller inverter on the east west split as it would be more efficient.

Still you both have what you have, you have produced more KWH so you will gain on the FIT payments, but you friends system will produce a longer, more even power curve throughout the day, making his power more usable therefore probably saving him more on his electricity bill, and your system will probably "peak" higher than his at around 1pm, but if you are not using 4KW it just gets exported.

I hope this helps.


Not immediately obvious why the difference. You could try and see whether Sunny Design predicts it. Perhaps you have better afternoon/evening sun where you are than morning sun. West coast?


I would argue east over west to make advantage of coolness in the mornings and less haze due to less polution than at the end of the day.
If you were able to look at the differences between the east and west strings it would be more useful.
The difference may be down to the hyundi panels, but, as above many factors are involved.


Since your last thread your Friends system to 27th has produced 1040kWh

My 3.84kWp south east essex 16 Suntech 240W 8East/8West on a 4000TL has produced 1099kWh in the same period (assuming the readings you gave were at the end of the day you posted).

So a difference of 49kWh, not much assuming weather is very similar then maybe his roof is steeper pitch.

I also have some shading on the west side from a tree between 18:15 to 19:30 at this time of year that takes a chunk out.

As for the difference between your systems, Your Inverter will be running more efficiently for a shorter time period so will produce more (assuming the weather averages out). But us with split systems will have more savings on our bills due to startup at 5:15am and shutdown at 20:40 at the moment. (If this will translate to a shorter inverter life who knows).
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I would go for a 50-50 split with a slightly under-spec inverter if the installation cost is roughly the same. If you're looking at a few hundred quid extra for scaffolding etc, sticking them all on the same roof surface might well make more sense.
Agree on scaffold cost there .

it will reduce overall cost if scaffold price is halfed.

So your over all ROI will be better and payback quicker with panels all on one roof unless you can get scaffold very cheap.
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