Estimate your potential savings.
Adjust the system, location, electricity use and tariff to see an illustrative result.
Your sunny spot
Your electricity & costs
Lower this if you’re out during daylight. It is an assumption about timing; annual household use alone cannot predict it.
YOUR ILLUSTRATIVE ANNUAL SAVING
Central estimate: £81 a year
No payment assumed for surplus electricity.
Yellow: used in the home · Grey: surplus
Explore the product database See every assumptionWhat this calculation assumes
This is a simple planning model, not a site survey or a live PVGIS calculation. Regional starting yields are our illustrative assumptions: south 1,000, Midlands/Wales 900, northern England 850, Scotland 800 and Northern Ireland 850 kWh per kWp each year.
We multiply by panel size and approximate factors for direction (south 1; south-east/west 0.93; east/west 0.8; north 0.55), angle (tilted 1; upright 0.75; flat 0.85) and shade (clear 1; passing 0.85; sustained 0.5). These generic factors cannot model the interaction of direction, angle, obstructions and season at your home.
Savings = generation used at home × your unit rate. Used generation cannot exceed the annual household demand entered. The ±20% range simply shows sensitivity to the central estimate; it is not a statistical confidence interval and actual outcomes can fall outside it. Payback uses the central estimate. We exclude export payments, batteries, tariff changes, degradation, finance, maintenance and time-resolved inverter clipping.
An input above 800Wp does not increase the permitted AC output. Use a detailed assessment for larger or more complex arrays. Try the European Commission’s PVGIS tool for a location-specific starting point.