What this calculator models
Solar PV with a battery is now a financial decision rather than an environmental one — modern panels and batteries pay back well within their warranty period for most UK homes, given a sensible tariff. The complication is that the answer depends heavily on three things almost no public calculator surfaces: your real daily consumption profile, your tariff structure (flat rate vs time-of-use vs export-rich), and how much of your generation actually offsets imports rather than spilling cheap onto the grid. This calculator separates each layer so you can see what the panels do, what the battery does, and what tariff arbitrage adds on top.
Inputs
- Roof area available (m²) and orientation
- Roof pitch and shading
- Annual electricity consumption (kWh)
- Daily consumption profile (high-day, high-evening, mixed)
- Current import tariff (p/kWh)
- Export tariff under Smart Export Guarantee
- Battery capacity considered (0, 5, 10, 15, 20 kWh)
- EV charging at home (yes/no, miles per year)
Outputs
- Annual generation estimate (kWh)
- Self-consumption rate (PV-only, PV+battery)
- Annual import-cost saving
- Annual SEG export revenue
- Annual time-of-use arbitrage revenue (where battery applicable)
- Payback period (PV-only, battery-only, combined)
- 25-year NPV
- Carbon-saving estimate (tCO2e over 25 years)
Typical payback band: 6-10 years for PV-only on south-facing UK roofs, 9-13 years for combined PV+battery, sub-6 years for export-rich arrangements with EV charging on time-of-use tariffs
Best for: Owner-occupiers with south, southeast, or southwest-facing roof aspect, an annual electricity consumption above 3,500 kWh, and either an EV or willingness to shift consumption to align with generation.