Payback is a division sum. Both numbers in it are currently unknown, and one of them is unknowable without knowing your household.
Payback is the all-in cost divided by what you save each year. Every plug-in solar payback figure you have read is someone filling in both of those.
This is the part that changes payback the most, and you can't opt out of it.
The output arrives between late morning and mid afternoon. Plenty of households are out for exactly that window, and anything not used in the moment goes back down the wire for nothing. A battery is the usual fix for that.
It is also the one fix the rules do not allow. Batteries sit outside the approved class entirely, sold alone or built into a kit. Consultation respondents said withholding storage cut what consumers could expect to get back. The exclusion stayed.
The households with the best payback are the ones at home during the day. If your house is empty from eight to six, a plug-in panel without storage is exporting most of what it makes, and no advertised payback figure accounts for that.
If you have had one running long enough to see it on a bill, we would like to know.
This is the only way this site gets real UK numbers. We will publish ranges once we have enough of them to be worth publishing, with the date they were collected, and we will say how many they are based on. Nobody's details are published and no seller sees your message.