Water Heating Energy, Time & Cost
Find the energy, time and cost to heat a volume of water with an electric heater or boiler, free online.
About this calculator
Energy = mass × 4.186 kJ/kg·K × temperature rise (≈ 1.163 Wh per litre per °C). Divide by heater power and efficiency for time. Heating a 150 L tank by 40 °C needs about 7 kWh. Heat-pump water heaters use 2–4× less electricity.