What could solar, a battery or a heat pump save you?

Answer a few questions about your home and see an estimate of your yearly savings and carbon saved. Figures update as you go.

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How we work this out
  • Solar output uses 850 kWh per kWp per year for a south-facing roof in South Yorkshire, adjusted for direction and shading.
  • The battery stores spare solar for the evening at 90% round-trip efficiency, and on a cheap-hours tariff also charges from the grid. The suggested size is where going bigger stops paying: an extra kWh would add less than £6 a year.
  • Heat pump efficiency (SCOP) for each design flow temperature is averaged from real-world monitored heat pumps on HeatpumpMonitor.org: 4.7 at 35°C, 4.2 at 40°C, 3.7 at 45°C, 3.2 at 50°C and 2.7 at 55°C. Hot water is heated to 55°C at 3.0.
  • Boiler efficiency: 87.5% under 10 years old, 82.5% at 10–20, 75% over 20 (70% for oil). Gas 7.97p/kWh and 29.68p/day standing charge (Ofgem cap, Oct 2026), oil about 120p/litre, LPG about 75p/litre.
  • Tariff rates are typical figures checked in October 2026 and vary by region. Solar and battery figures over 25 years and heat pump figures over 20 years assume prices rise 3% a year.
  • This is an estimate, not a quote. Your real savings depend on your home, how you use energy and your tariff.