Free UK Solar Yield Calculator
Estimate how much electricity your solar panels will generate using official MCS irradiance data. Enter your postcode, roof details, and system size for an accurate yield estimate based on your UK location.
Solar Yield Calculator
Estimate your annual solar generation using official MCS data
A solar yield calculator estimates the annual electricity output (kWh) of a solar PV system based on your location, roof orientation, tilt angle, system capacity (kWp), and shading conditions. In the UK, a typical 4 kWp residential system generates between 3,400-4,200 kWh per year depending on location, with south-facing roofs in southern England producing the highest yields. This calculator uses the MCS MIS 3002 methodology, the industry-standard approach used by all MCS-certified installers in the UK. Looking for business ROI instead? Try our ROI Calculator.
How we calculate your solar yield
Our calculator uses the official MCS (Microgeneration Certification Scheme) methodology from MIS 3002, the same standard that MCS-certified installers use to estimate solar PV performance for customers.
The formula: Annual generation (kWh) = System size (kWp) × Kk value × Shading factor
Location-specific data: The Kk value (kWh/kWp) comes from MCS irradiance tables derived from the European Commission's Climate-SAF PVGIS dataset. The UK is divided into 21 zones, each with irradiance values for every combination of roof pitch and orientation. Your postcode determines which zone is used.
Financial estimates: Savings are calculated using the Ofgem energy price cap rate (27.7p/kWh, Q1 2026) for electricity you use directly, plus the Smart Export Guarantee (SEG) rate of 12p/kWh for surplus energy exported to the grid. Lifetime figures account for 0.5% annual panel degradation over 25 years.
Frequently asked questions
What is the MCS Kk value?
The Kk value represents the expected annual electricity generation per kilowatt peak (kWh/kWp) for a specific location, roof pitch, and orientation. It accounts for local solar irradiance levels across the UK. South-facing roofs at 30-35° pitch typically have the highest Kk values, ranging from 900-1,100 kWh/kWp depending on region.
How accurate are these estimates?
The MCS irradiance data is derived from satellite measurements (PVGIS) and is the industry-standard method for estimating solar yield in the UK. Real-world performance varies with weather patterns, equipment quality, inverter efficiency, and installation factors. These estimates are typically within 10-15% of actual yields.
What is the Smart Export Guarantee (SEG)?
The SEG requires energy suppliers with 150,000+ customers to offer a tariff for small-scale renewable electricity exported to the grid. Rates vary by supplier, typically ranging from 3-15p per kWh. We use 12p/kWh as a typical mid-range rate.
What about the Boiler Upgrade Scheme (BUS) grant?
The Boiler Upgrade Scheme provides grants toward the cost of heat pumps and biomass boilers but does not cover solar PV directly. However, if you're installing solar alongside a heat pump, the BUS grant can reduce the overall project cost. For solar-only installations, the main financial benefits come from electricity bill savings and the SEG export income calculated above.
What self-consumption ratio should I use?
Self-consumption depends on your household's electricity usage patterns. A typical home without battery storage self-consumes around 30-50% of generated electricity. With a battery, this can rise to 60-80%. We default to 50% as a reasonable middle ground.