How the calculator works
Enter your typical annual electricity spend, the type of farm building you're considering, and your roof area. The calculator estimates a sensible system size, models annual generation based on UK irradiance, applies a self-consumption ratio appropriate to your building type, and produces an indicative cost, annual saving, simple payback, and 25-year cumulative return.
These numbers are indicative. Your actual install economics depend on roof orientation, shading, structural condition, DNO grid capacity, and the specifics of your meter data. We deliver full desk feasibility studies within 7 working days of receiving your half-hourly meter data — request one here.
How the calculator estimates your figures
The calculator uses 2026 UK averages: cost per kW £800 for system sizes above 100 kW (£900 below 100 kW); 900 kWh/kW/yr generation for UK mid-latitude orientation; grid retail price 24p/kWh; SEG export tariff 11p/kWh average; self-consumption ratio specific to your building type (dairy parlours at 92%, grain stores at 45%, etc.). The "after AIA" payback assumes you're an incorporated farm at 25% corporation tax claiming 100% Annual Investment Allowance — the largest single tax efficiency available for capital expenditure on solar PV.
The calculator deliberately doesn't model: battery storage (typically pulls payback in by 4–6 months for grain stores and seasonal-load farms); ground-mount lease income (a separate decision); SFI biodiversity stacking; supermarket supplier-audit value; or fleet electrification savings. These all push real-world economics in the right direction.