Water Heating Calculator

Your details

Total volume of water to be heated. 1 US gallon = 3.785 L.
L
Temperature of the water before heating starts.
°C
Desired final water temperature. 60 °C is typical for a domestic hot-water tank.
°C
Rated heating power of the element, burner, or heat pump.
kW
How much of the rated power actually heats the water. Electric elements: 95-99 %. Gas water heaters: 60-80 %. Heat pumps: 200-400 % (COP mode).
%
Cost of electricity per kWh. Used to calculate the running cost. Leave at 0 to skip cost.
$/kWh
Energy requiredFast (under 30 min)
1,883.7kJ

Total heat energy the water must absorb

Energy (kWh)0.5233kWh
Heating time11.6min
Heating time (hours)0.19h
Running cost0.0872$
Temperature rise45°C
Energy (kJ)1,883.7
Time (min)11.6

Raising 45.0 °C requires 1884 kJ over 12 min.

  • Your heater needs to deliver 1884 kJ (0.523 kWh) of heat to the water.
  • At the rated power and 90 % efficiency, heating takes about 12 minutes.
  • The estimated electricity cost for this heating cycle is $0.087.

Next stepTo reduce heating time, increase heater power. To cut running costs, improve insulation or switch to a heat pump.

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