In short
Usually, yes. An 800 W plug-in kit facing south on a railing (90°) makes about 592 kWh a year in London. If your home uses 2,500 kWh a year, about 336 kWh of that output is used at home (57%). At 26.32 p/kWh, that saves about £88 a year, so a £700 kit pays for itself in 8.1 years. Facing east or west, shading or low use in the day all stretch that out.
How the calculator works
- Yield: PVGIS, the solar tool of the European Commission's Joint Research Centre (JRC), PVGIS-SARAH3 database, 2005–2023 average, with 14% system losses (cables, inverter, dirt).
- Hour by hour: For each month we use four typical days, from dull to sunny, and cap every hour at the inverter limit. Anything above it is lost. Short spikes within an hour aren't modelled, so the loss to the 800 W limit can be a little higher.
- Demand: No openly licensed British household profile was available, so we use the German BDEW H25 standard profile (2025) to spread your annual use over months and hours. Within each hour there is an always-on load plus short peaks (kettle, washing machine). That's why not every unit from the balcony replaces one from the grid.
- Always-on load: If you leave it empty we assume 57 W. We set this, and the peaks, so that the calculator gives self-use shares similar to the government's two worked examples (62% at 30° south and 72% at 90° east/west) under the same conditions. If you know yours, enter it: a smart or digital meter shows the current power in W at night.
- Savings: Every unit you use at home saves the unit rate. Exported power earns nothing unless you enter an export payment. Panels lose 0.5% of their output a year. After 15 years we add a new inverter, at a third of the kit price, costed at 75% of today's price, as HTW Berlin does; the UK impact assessment assumes £100 after 10 years instead.
- Kit price: The default follows the number of panels: £700 for two, about £200 for each extra panel, based on the kits Which? listed in September 2026. It's an estimate, so enter what you actually pay.
- Verdict in the result: paid back within 10 years means “worth it”, later but within the period “only just”, otherwise “not worth it”. The 10-year threshold is our own assumption.
- Accuracy: The yield is a long-term average, so single years differ. Self-use comes from a standard profile, and your home may differ a lot. Shading and how much you use during the day matter most.
Yield by city and orientation
Annual yield of 800 W of panels in kWh, PVGIS 2005–2023 average, without shading and before the 800 W limit, so a few kWh more than in the calculator above.
| City | South 90° | South-east 90° | East/west 90° | South 35° | Flat |
|---|---|---|---|---|---|
| London | 594 | 559 | 408 | 815 | 676 |
| Birmingham | 568 | 530 | 390 | 774 | 644 |
| Manchester | 517 | 484 | 361 | 709 | 596 |
| Leeds | 567 | 525 | 384 | 761 | 626 |
| Newcastle | 575 | 525 | 379 | 760 | 615 |
| Bristol | 591 | 546 | 410 | 818 | 684 |
| Plymouth | 635 | 584 | 441 | 897 | 750 |
| Cardiff | 596 | 540 | 412 | 833 | 696 |
| Glasgow | 505 | 461 | 345 | 681 | 568 |
| Edinburgh | 543 | 496 | 360 | 720 | 588 |
| Aberdeen | 541 | 489 | 347 | 712 | 575 |
The rules in Great Britain
- Legal since 27 August 2026 in England, Wales and Scotland (SI 2026/848). A plug-in kit may have an AC output of up to 800 W and must meet the government's product specification (inverter up to 800 VA).
- Plug it straight into a wall socket. The product specification does not permit extension leads or multi-way, RCD or travel adaptors, and the plug must carry that warning.
- Panels: up to 2,000 W of panels (at most four) on the one 800 VA inverter. Above 960 W, makers must advise you to consider a professional check of your wiring before you install the kit.
- One kit per household (EREC G98). The product specification says telling your network operator (DNO) when you connect or disconnect the kit is mandatory; the kit's instructions explain how.
- No battery: the product specification excludes plug-in solar with batteries, so the calculator has no battery option for Great Britain.
- Export: the Smart Export Guarantee needs MCS (or equivalent) certification and an export meter, so plug-in kits usually get nothing for exported power.
- Northern Ireland: as of 4 November 2026, Northern Ireland had not changed its rules, so plug-in solar is not legal there yet.
Frequently asked questions
Are plug-in solar panels worth it?
Mostly, if they face roughly south and you use power during the day. In London, an 800 W kit facing south on a railing saves about £88 a year at 26.32 p/kWh and pays back a £700 kit in 8.1 years.
How much are plug-in solar panels?
In Great Britain, two-panel kits listed by Which? in September 2026 cost about £456–£899. The government's impact assessment, based on European prices, puts 800 W kits at about £400–£600 before installation. Enter your own price in the calculator.
Sources
- PVGIS 5.3, European Commission Joint Research Centre (JRC)
- SI 2026/848 (legislation.gov.uk)
- DESNZ: Plug-in Solar Device Interim Product Specification v2 (July 2026)
- DESNZ: Plug-in solar, final-stage impact assessment (2026)
- Which?: Plug-in solar panels, everything you need to know (updated 16 September 2026)
- Ofgem: energy price cap unit rates (1 Oct – 31 Dec 2026)
- Ofgem: typical domestic consumption values, decision (May 2026)
- Ofgem: Smart Export Guarantee, guidance for generators
- BDEW: standard load profiles (H25, 2025)
- HTW Berlin: plug-in solar simulator, method (2024, German)
- GeoNames (CC BY 4.0): postcodes and cities