How to calculate your solar panel savings — UK guide (2026)
Solar panel savings depend on four variables: how much electricity your system generates (determined by your postcode’s irradiance, roof orientation, shading, and system size), how much of that electricity you consume yourself, how much electricity currently costs you, and how much your energy supplier pays you for surplus electricity via the Smart Export Guarantee.
Generation: postcode and orientation matter most
The UK’s solar irradiance varies significantly from north to south. Using PVGIS data from the European Commission, a 4 kWp system in Cornwall (TR) generates around 4,400 kWh/year, while the same system in Shetland (ZE) generates roughly 3,400 kWh — a 30% difference. Roof orientation is equally significant: a south-facing roof achieves 100% of the potential yield, while a north-facing roof achieves only 65%, making it rarely viable economically.
Self-consumption and battery storage
Without battery storage, a typical household self-consumes about 35% of the electricity their panels generate — the rest is exported to the grid. Battery storage can increase self-consumption to 55–75%, improving the economics significantly because import and export rates differ (you save 27p/kWh on electricity you would have bought, but only earn ~15p/kWh on electricity you export).
The 2026 Ofgem price cap
From April to June 2026, the Ofgem energy price cap sets the unit rate at 27.03p/kWh and the standing charge at 61p/day. The calculator uses this rate as the default. If your actual tariff differs, enter your own rate for a more accurate figure.
MCS certification — why it matters
To participate in the Smart Export Guarantee, your installation must be carried out by an MCS-certified installer. MCS certification also gives you access to the Boiler Upgrade Scheme grant (for combined heat pump and solar installations) and the installation will carry a minimum 5-year warranty on workmanship.