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UK Plug-In Solar Savings Calculator

Pick your nearest city and describe where the panel would go. You get a yearly saving, a payback time and a month by month picture. Every assumption is shown, and you can change all of them.

Verified 21 Sep 2026
Verified 21 Sep 2026

How much does plug-in solar save in the UK? For an 800 W kit on a south-facing balcony in London, our estimate is about £125 a year at today's 26.32p per unit, if you use 80% of what it makes. That is a best case. Shade, a north-facing wall or an empty house in the daytime all bring it down, and the calculator below shows by how much.

Calculator

Sun data is for the city centre. Somewhere within about 50 miles will be close.

Panel size (watts)

The rules cap the inverter at 800 W, so 800 W is the biggest kit this page covers.

Where it goes
Which way it faces
Shade

We take off 10% for some shade and 25% for heavy. Those are our round numbers, not measured ones.

Ofgem cap, 1 Oct to 31 Dec 2026. Check your own bill.

A placeholder. Put in your real quote.

Our assumption. 80% suits a home where someone is in most of the day. If everyone is out from 8am to 6pm, try 50%.

Estimated yearly saving
£125
Payback
3.2 yrs
Output
595 kWh
10-year net
£852
Output by month (kWh)
JFMAMJJASOND

An estimate, not a quote. It counts only the power you use yourself.

Check the UK rules before you buy

How we work out the number

There are three steps, and you can check each one yourself.

  1. Output. We asked the EU's PVGIS tool how much an 800 W panel makes in each of 12 UK cities, for each tilt and direction, then scaled it for the panel size and shade you pick.
  2. Saving. Output, times the share you use at home, times the price you pay per unit.
  3. Payback. The kit price divided by the yearly saving.
saving = kWh per year × share used at home × price per kWh
payback = kit price ÷ saving
10-year net = saving × 10 - kit price

What we assumed

ItemValueWhere it comes from
Sun dataPVGIS-SARAH3PVGIS v5.3, fetched 2026-09-21
System losses14%The PVGIS default for cables, inverter and dirt
Electricity price26.32p per kWhOfgem cap, 1 Oct to 31 Dec 2026, Direct Debit, average for England, Scotland and Wales
Used at home80%Our assumption. You can change it.
Shade0%, 10%, 25%Our assumption. Rough steps, not measurements.
Kit price£400A placeholder, not a shop price
Export payment£0We have found no UK scheme that pays for it

We also leave out panel ageing and any change in energy prices. Electricity prices move every three months, and the government has taken VAT off electricity only until 31 Mar 2027, so the number on your bill may look different next year.

Why your real saving may be lower

The saving only counts power that your home uses at the moment it is made. An 800 W kit peaks around midday in summer. If the house is empty then, you are relying on the fridge, the router and standby loads to soak it up, and whatever is left flows out unpaid.

Direction matters more than most people expect. A vertical panel facing north makes about a quarter of what the same panel makes facing south. Try it in the calculator.

The government's own line is that households could save "up to £110" a year. Treat it as a ceiling. Our best case for London comes out a little higher because it assumes no shade and 80% use, and we do not know what GOV.UK assumed.

What to do with the answer

If the payback is under five years, the kit is probably worth a serious look. Between five and ten, it depends on how long you will stay in the home. Over ten, you are better off spending the money elsewhere. Then check the rules, and make sure the model you want is on the approved register before you pay. The cost page explains where the £400 price came from.

Questions people ask

How much can plug-in solar save?
It depends on where you live, which way the panel faces and how much power you use while the sun is out. With the starting values on this page (800 W, London, vertical and facing south, 26.32p per unit) the estimate lands around £125 a year. Move the inputs to match your home and it can go a good deal lower.
How much energy does a plug-in solar panel produce?
An 800 W kit on a south-facing balcony rail in London makes roughly 595 kWh over a year, going by PVGIS. A flat or angled panel makes more. A panel facing north makes well under half of that. How a plug-in panel makes power
Are plug-in solar panels worth it?
For a lot of homes the answer comes down to two numbers: what you paid for the kit and how much of its power you actually use. Put both in the calculator and look at the payback line. If it says more than ten years, think twice. Check you are allowed to fit one first
Why does the calculator say more than the government’s £110 a year?
Our starting values are generous on purpose so you can see the top end: a south-facing panel with no shade and 80% of the power used at home. GOV.UK calls its figure "up to" and we have not seen the assumptions behind it, so we cannot say why the two differ. Lower the "used at home" slider and the number drops fast. See the cost page
Does the calculator include payment for power I send back to the grid?
No. We have not found a UK scheme that pays for surplus from a plug-in kit, so the sum counts only the power you use yourself. If that changes we will add it and say so.
Is the £400 kit price real?
It is a placeholder for you to change. We do not have a checked shop price for an approved kit yet. Type in whatever you have been quoted. Where the £400 figure comes from
This is general information, not legal or electrical advice. If your socket or wiring is old, ask a registered electrician first.
Sources
  1. European Commission JRC: PVGIS v5.3 PVcalc API, PVGIS-SARAH3 radiation data, called for 12 UK cities on 21 Sep 2026. re.jrc.ec.europa.eu accessed 21 Sep 2026
  2. Ofgem: Energy price cap unit rates and standing charges, 1 Oct to 31 Dec 2026 (26.32p per kWh, Direct Debit, England, Scotland and Wales average). www.ofgem.gov.uk accessed 21 Sep 2026
  3. GOV.UK: Households can save as plug-in solar panels come to market, 26 Aug 2026. www.gov.uk accessed 21 Sep 2026
  4. DESNZ: Plug-in Solar Device Interim Product Specification, version 2.0, July 2026. assets.publishing.service.gov.uk accessed 21 Sep 2026