This calculator is designed to give you a reliable, realistic estimate — accurate enough to help you decide whether solar is worth pursuing — before you spend time sourcing and comparing installer quotes. The figures are built on current MCS installer cost benchmarks, Ofgem’s Q2 2026 unit rate of 24.67p per kWh, and regional UK irradiance data. That said, it produces estimates, not exact quotes. Your actual results will depend on your specific roof condition, the precise panels and inverter your installer specifies, your exact daily energy usage patterns, and which SEG tariff you register on. For a precise, binding quote, you’ll need an MCS-certified installer to survey your property in person. Think of this calculator as step one — it gives you the confidence to know whether the conversation with an installer is worth having.

The calculator draws on four main data sources, all updated for 2026. Installed system costs are based on MCS-certified installer benchmarks sourced from industry data published in early 2026, reflecting the post-0% VAT pricing environment. Electricity savings are calculated using Ofgem’s Q2 2026 standing tariff unit rate of 24.67p per kWh — the figure most UK households are currently paying. Solar output estimates for each UK region use irradiance data from PVGIS (the EU’s Photovoltaic Geographical Information System), adjusted per the roof orientation you select. The Smart Export Guarantee income estimate uses a conservative mid-range SEG export rate of 15p per kWh — below the best available rate of 27p (Octopus Flux, June 2026) but above the lowest-paying suppliers. The 25-year projection applies a 3.5% annual energy price escalation and a 0.4% annual panel degradation rate, both consistent with current industry modelling. All data points are reviewed and updated whenever official figures change.

Solar panels generate electricity from daylight, and the amount of usable daylight hours across the UK varies significantly by region. The south of England receives meaningfully more solar irradiance per year than Scotland or the north of England — not because it is always sunnier, but because it accumulates more peak sunlight hours across the year. A south-facing 4kW system installed in London or the South East typically produces around 3,800 kWh per year. The same system in Scotland generates closer to 3,100–3,200 kWh. That difference of 600–700 kWh per year represents roughly £170 in annual bill savings — a significant gap over a 25-year system life. The calculator applies a regional irradiance multiplier specific to your selected UK region, so your results reflect where you actually live rather than a UK-wide average that could meaningfully overstate or understate your output.

Because it is real, ongoing income that the majority of solar calculators simply do not show you — and leaving it out significantly understates the financial case for going solar. The Smart Export Guarantee is a government-backed scheme, introduced in 2020, that legally requires licensed energy suppliers to pay you for every kilowatt-hour of surplus solar electricity you export to the National Grid. You need an MCS-certified installation and a smart meter to register, but once you are on a tariff, the income is automatic and ongoing. At a mid-range rate of 15p per kWh, a typical 4kW system without battery storage earns approximately £270–£290 per year in export payments on top of your bill savings. At the best available rate (currently 27p per kWh with Octopus Energy’s Flux tariff), that rises to over £600 per year. Including SEG income in your results gives you a complete and honest picture of what solar is actually worth to you financially.

Yes. If you select “include battery storage” in Step 2, the calculator makes two key adjustments. First, it adds an estimated £4,200 to your total installation cost, reflecting the current 2026 price of a typical 9–10 kWh lithium iron phosphate (LFP) battery unit fully installed. Second, it increases your self-consumption rate from 45% to 75%, meaning you use a much greater share of the solar electricity you generate during the day — storing it for evening use — rather than exporting it to the grid at the SEG rate. This results in higher annual bill savings, a different payback calculation, and a meaningfully larger 25-year return. Battery storage is also currently zero-rated for VAT in the UK until at least March 2027, so the installed cost shown already reflects this saving. If you are unsure whether battery storage makes sense for your household, our guide to battery storage covers the decision in detail.

No — and that is a deliberate decision on our part. This calculator gives you your complete results immediately: recommended system size, number of panels, estimated installation cost, annual bill saving, SEG export income, total annual financial benefit, payback period, 25-year return, and CO₂ savings. All of it, upfront, with no email address required, no account creation, and no phone number. We believe you should be able to access honest information and make an informed decision before anyone contacts you. If after reviewing your results you would like to take the next step, we signpost you to the MCS certified installer directory at mcscertified.com, where you can find vetted local installers and request quotes on your own terms.