Solar PV questions from a newbie...

Verdigris

Can a 390W panel ever produce more than 390W, or is there some reporting error somewhere?

Panels have an output tolerance stated on them as +/-x%. The more reputable makers only have a positive tolerance, typically 5%, so a 390Wp panel may produce up to 420W in optimal conditions. This will gradually decline over the years by the percentage stated on the specification, although it has recently been found that degradation is often slower than previously forecast.

Also, temperature affects output. The cooler the panel the higher the output, so if you have an optimal angle for winter sun you may get your highest spot outputs in the colder months. You don't get it for so long, obviously.

QrizB

Officer_Dibble said:

Thanks for the kettle recommendations, I'll do some research - the neostar permatherm looks ideal at a glance.

The panels have generated over 5kW on a couple of occasions between clouds today, so it looks like they're all working. Could have been a battery filling thing as Magnitio suggests. Can a 390W panel ever produce more than 390W, or is there some reporting error somewhere?

You can (briefly) benefit from cloud edge effect, where nearby clouds scatter sunlight and make it *brighter* than full sun:

https://sky-lights.org/2020/04/20/cloud-edge-effects-on-solar-arrays/

Also, at this time of year a panel in the UK can be colder than STC which will increase its output fractionally.

Magnitio

QrizB said:

You can (briefly) benefit from cloud edge effect, where nearby clouds scatter sunlight and maske ut *brighter* than full sun:

https://sky-lights.org/2020/04/20/cloud-edge-effects-on-solar-arrays/

Also, at this time of year a panel in the UK can be colder than STC which will increase its output fractionally.

That might explain why the peak output from my array yesterday with a completely cloudless sky was about 4.25kw and yet today with some clouds it spiked at well over 5kw on a number of occasions.