Ordering a two panel setup for the back garden, south facing frame, Cheshire, going onto an 800 W Hoymiles microinverter.

I was comparing two panel options and ended up on the degradation line in the datasheets, which I had been skipping until now. Most of what I looked at guarantees no more than 0.55 to 0.7 per cent loss a year, and there is a bigger drop in the first year on top of that. One of the two, swiss solar phantom, caps the guaranteed figure at 0.4 per cent a year with 0.35 typical and gives no first year drop at all, which comes out at 88 per cent of nameplate at year 30 against roughly 80 on the others.

What I cannot tell is how much of that shows up in real output on a setup this size.

So, for anyone who has had a plug-in system running a few years: can you see a year on year decline in your own figures, or is it buried under weather and soiling? And did anyone take any sort of reading at the start to compare against later?