UK Solar Savings Calculator
See your payback period, 25-year net saving and ROI - updated with current Ofgem price cap rates.
Solar pays back - eventually. This calculator turns your roof direction, system size, electricity usage and battery plans into a concrete payback figure and a 25-year ROI estimate. You can even model DIY vs professional install costs, so you see which path actually makes financial sense for your home.
Your Setup
Enter your electricity usage and system specs. We calculate everything else - payback years, annual and 25-year savings, ROI and self-consumption.
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⚡ How we model self-consumption
Without a battery, a typical UK home uses about 50% of the electricity its panels generate (the rest is exported at the SEG rate). Adding a battery pushes that to roughly 70%, so you use more of your own free power instead of buying from the grid. The calculator reflects that in your annual saving and payback figure - and it's why a modest 5kWh battery can cut payback by 1-3 years on winter-heavy usage patterns.
Frequently asked questions
How accurate is this solar savings calculator?
This calculator uses UK averages (950 kWh/kWp generation, Ofgem price cap electricity rates, typical direction factors) to give a realistic estimate. Actual savings vary with weather, your specific roof orientation and pitch, shading, and how much electricity you use during daylight hours. We'd expect the annual saving to be within about 20% of real-world results for a south-facing roof with no shading.
What payback period should I expect for UK solar?
A typical UK solar installation pays for itself in 8-14 years depending on system size, roof direction, installation type (DIY vs professional), and whether you add battery storage. DIY installations often achieve 8-10 year payback; professional installs tend toward 12-15 years. Adding a battery improves self-consumption and can reduce payback by 1-3 years in winter-heavy usage patterns.
Is a 4kW solar system enough for a UK home?
4 kWp is the sweet spot for a typical UK 3-bed semi-detached house. It generates roughly 3,400-3,800 kWh a year depending on direction and pitch, which covers 80-100% of a typical household's annual electricity needs. A 3-bed home with gas heating uses about 2,700-3,600 kWh of electricity per year, so 4 kWp is a good match.
Should I add battery storage to my solar system?
A battery boosts your self-consumption from about 50% to 70%, meaning you use more of the electricity you generate rather than exporting it cheaply. With SEG export rates around 12p/kWh versus electricity at 26.11p/kWh, every kWh you store and use yourself saves roughly 14p. A 5kWh battery costs around £2,000-2,500 installed and typically adds 1-3 years to payback while improving your long-term savings.
Do I need to tell my energy supplier about solar panels?
Yes. You must notify your Distribution Network Operator (DNO) before connecting any generation to the grid. For systems under 3.68 kW (single-phase) you use a G98 notification, which is a simple online form your installer or electrician can submit. Systems over 3.68 kW need a G99 application, which takes longer and may require a network study. You also need to register for the Smart Export Guarantee (SEG) with a participating supplier to get paid for exported electricity.
Get paid for your excess solar
Octopus Energy pays one of the most competitive SEG rates in the UK and makes switching simple. Use our referral link for Octopus credit when you switch, then sign up for their SEG import-only or export tariff to get paid automatically for every kWh you export.
Once you know your panel count, Sunstore's UK solar panel shop has matched kits from JA Solar, Longi and Jinko at trade prices.
Switch to Octopus Energy → Browse Sunstore solar kits →
Affiliate disclosure: DIY Solar UK earns a commission from qualifying purchases via these links, at no extra cost to you.
Rather have it installed?
If DIY is not your thing, tell us about your roof and timeline and we will come back to you with installer options for your area - we do not install anything ourselves, and right now your enquiry comes to us rather than straight to a network. See our privacy policy for the details.
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