Plug-in solar kits are new enough that UK retail prices aren't settled yet. So instead of guessing a number, here's the method you can use on any kit you find. It also has real numbers for the savings side.
How much power can an 800 W kit make?
ByMySun's own figures put a well-sited UK solar array at about 900 kWh per kWp each year. An 800 W kit is 0.8 kWp, so at that rate it makes about 720 kWh a year. That's the ceiling for a kit angled well, like a roof-mounted panel.
Why leaning it on a wall makes less
A panel angled toward the sun catches far more light than one leaning flat against a balcony rail or wall. That's how a roof panel is normally angled. The 720 kWh a year figure assumes good, roof-like angling. A propped-up balcony panel will make less than that, so treat 720 kWh as a best case, not a guarantee.
What is that power worth on your bill?
Because an 800 W kit is small, it mostly covers power your house is already drawing. That includes things like the fridge and standby devices. So you use nearly all of it yourself rather than exporting it. At the Ofgem cap import price of 26.11p per kWh, 720 kWh a year works out to about £188. That's an estimate built on the assumptions above, not a promise.
A worked example, step by step
Here's the maths in one place, clearly labelled as an example, not a real quote. Say a compliant kit costs around £600, just to have a number to work with. At an estimated £188 a year in savings, that's a payback of a little over three years. That's before you even count the 0% VAT relief on qualifying kits, which runs until 31 March 2027. Swap in the real price you're quoted and redo the sum.
The quick version
- An 800 W kit can make about 720 kWh a year if well angled.
- That's about £188 a year at the Ofgem cap price.
- 0% VAT applies to qualifying kits until 31 March 2027.