Water Heating Calculations

Energy consumption kWh for water heating

Cold water temperature,

=  °C, °F or K

* Tap water: winter 4-15°C (39-59°F), summer 16-20°C (60-68°F)

Warm water temperature, °C

=  °C

* Comfortable temperature for body and handwashing is 35-40°C (95-104°F), boiling point is 100°C (212°F)

Volume or mass of water,

=  L

* Volume in liters is equal to weight in kilograms. Gallon US = 3.78541178 L. Gallon GB = 4.54609188 L.">Volume or mass

Efficiency factor of heater, %: 

=  %

* Efficiency factor: electric kettle 95-98%, boiler 95-99%, electric range 50-70%

Energy consumption:  kW·h ( Gkal)

* How much energy will count by electricity meter

Water Heating Costs

Electricity Tariff, per kWh: 

=  $ / kWh

Energy Cost:  $

Heating time

Heater Power, kW: 

= kW   ( W)

Time:  h  m  s  (or  h)

Link to this calculation:  

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This calculator helps to know how much money, energy and time one spends to heat the water. You don't need any formulas or coefficients: simply enter your data and receive the answer.

To calculate the consumed electricity is necessary to specify the temperature of the hot and cold water, as well as its volume (mass). You can specify the efficiency of the heating device, if you know it. If you set 100% efficiency, then the calculation shows only useful power that you spend on water heating. The calculation will give the full power consumed from the network if you specify the real eficiency factor.

In order to calculate the full cost of water heating, you must specify your electricity tariff in $ € £ ¥.

To estimate how much time it takes for heating you should enter power of electrical device which you use to heat water. The power indicates in kilowatts (kW). The power is often shown on the device, as well as its user manual or passport.


Boiling water in an electric kettle

I usually pour into the kettle water at room temperature of 20°C to the level of 1 liter and always I bring to boiling (100 degrees). Power of the kettle is 2 kW. A simple calculation shows that the boiling spent approximately 0.1 kWh (kilowatt hours) of electricity, 3 minutes of time, and according to Germany rates, 2 cents of money.

So, every tea drinking adds 2 cents to the electricity bill, but it is much less than the price of tea or coffee.

Water heating in storage water heater

When I taking a shower I completely use all hot water from the storage heater. In winter, the heater warms the cold water from the 5 to 45 °C. The volume of the reservoir is 80 liters. With power of heaters 2 kW, fresh water in the tank will heat for 2 hours, it takes approximately 4 kW of electricity and 1 € for its payment. In summer the water heates from 18 to 45 °C.

This means that every showering takes 1 € in the winter, and in the summer – 0.7 €, not counting the cost of cold water.