Key takeaways
- • Plug-in solar in Great Britain is limited to a maximum output of 800W.
- • Savings depend heavily on how much electricity you use during daylight hours.
- • Permission may be required if you rent, lease or live in a managed building.
Savings come from electricity you do not buy. That makes self-consumption, not panel size, the main driver.
The basic sum
Annual saving = generated kWh x share you consume x your unit rate. An 800W system generating 650 kWh, with 70 percent self-consumed at 25p, saves about £114 a year. The same system with only 40 percent self-consumption saves about £65.
Typical UK ranges
- 400W portable kit: £35-£70 a year
- 600W garden or wall kit: £60-£110 a year
- 800W balcony or roof kit: £90-£165 a year
Improving the number
Run the dishwasher, washing machine and tumble dryer in daylight. Charge laptops, tools and e-bikes during the day. If you have a battery station or home battery, store the midday surplus. Every one of these moves shifts consumption under the generation curve.
What you should not count on
Export payments. Most small plug-in systems are not registered for a Smart Export Guarantee tariff, so exported units earn nothing. Treat any export income as a bonus, not part of your payback plan.
Use the savings calculator to enter your region, orientation, shading and tariff and see a low, central and high scenario over ten years.
Frequently asked questions
Sources
Fact-check status: reviewed. Read our editorial policy. General information only — not electrical, legal or financial advice.