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Solar Panel Savings Estimator — UK Generation & Cost Savings
Estimate how much electricity solar panels could generate on your roof and calculate potential annual savings based on UK conditions.
Roof Details
Usable south-facing (or nearest) roof area
Electricity & Usage
Ofgem Q3 2026 cap: 26.11p/kWh (1 Jul–30 Sep 2026; check your tariff)
30-50% without battery, 70-80% with battery
Best 2026 flat rates ~12p/kWh; up to ~30p on time-of-use tariffs
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How We Calculate This
This estimator calculates how many solar panels can fit on your available roof area, the total system size in kWp, and the expected annual electricity generation based on your UK location and roof orientation.
The calculations
Number of panels = Available roof area ÷ Panel area (m²)
System size (kWp) = Number of panels × Panel wattage ÷ 1000
Annual generation = System kWp × Regional kWh/kWp × Orientation factor
This follows the MCS MIS 3002 method (annual generation = kWp × Kk × shading factor). The regional kWh/kWp (Kk) figures below are derived from MCS / PVGIS irradiance data and are already net of system losses — the standard performance ratio (~0.8, covering inverter, cabling, temperature and soiling losses) is built into the published yield, so no extra loss factor is applied.
UK generation figures (net kWh per kWp per year)
- South England: ~1,050 kWh per kWp per year
- Midlands & Wales: ~950 kWh per kWp per year
- North England: ~900 kWh per kWp per year
- Northern Ireland: ~880 kWh per kWp per year
- Scotland: ~850 kWh per kWp per year
Savings calculation
Your savings come from two sources: electricity you use directly from the panels (saving you the full retail electricity price), and excess electricity exported to the grid under the Smart Export Guarantee (SEG). The self-use percentage depends on your daytime electricity consumption and whether you have battery storage — typically 30-50% without a battery and 70-80% with one.
Smart Export Guarantee (SEG)
We use a default SEG rate of 12p/kWh for exported electricity, reflecting the best flat rates available in 2026 (Octopus Outgoing and OVO around 12p/kWh). Rates are supplier-set and not capped, ranging from around 1p up to about 30p/kWh on time-of-use export tariffs. Check the latest SEG rates from your energy supplier and adjust the rate above to refine your estimate.
Frequently Asked Questions
In the UK, solar panels typically generate 850-1,050 kWh per kWp installed per year, depending on your location and roof orientation. These MCS yield figures are already net of system losses (inverter, cabling, temperature and soiling). A typical 4kWp system (10 standard panels) in the Midlands would generate approximately 3,800 kWh per year — enough to cover around half of an average household's electricity consumption.
The Smart Export Guarantee (SEG) is a UK government scheme that requires large energy suppliers to pay households for surplus electricity exported to the grid from solar panels and other small-scale renewable generation. Rates are set by suppliers (not capped by Ofgem) and vary widely — from around 1p up to about 30p per kWh on time-of-use tariffs. As of 2026 the best flat rates are around 12p/kWh (Octopus Outgoing and OVO SEG Beyond), with E.ON near 10.5p. You need a smart meter to claim SEG payments, and you can use a different supplier for export than for import.
A standard 400W solar panel measures approximately 1.7m x 1.0m (1.7-1.8m²). A typical UK semi-detached house has around 15-20m² of usable south-facing roof, which can fit 8-11 panels (3.2-4.4kWp). You need to account for roof windows, vents, and maintaining access space around the panels.
Yes, significantly. South-facing roofs get the most sunlight and generate the most electricity (100% output). South-east or south-west facing roofs generate about 95% of optimal. East or west facing roofs generate about 85%. North-facing roofs are generally not recommended as they only generate about 55% of optimal output.
As of 2025-2026, a typical 4kWp solar panel system (10 panels) costs approximately £5,000-£7,000 installed. VAT on solar panel installation in a residential property is currently 0% (zero-rated under the HMRC energy-saving materials relief) until 31 March 2027, reverting to the 5% reduced rate from 1 April 2027. Larger systems of 6-8kWp cost £7,000-£10,000. Battery storage adds £2,500-£5,000. Payback periods are typically 8-12 years depending on usage patterns. Solar PV can also improve your EPC rating — try our EPC rating estimator (/insulation/epc-rating-estimator/) to check.
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Last updated: June 2026
Verified against UK standards · estimates only, confirm with your supplier.