Enter the mass of water, specific heat capacity of water, and the change in temperature, along with the voltage, current, and time into the calculator to determine the kettle efficiency.

Kettle Efficiency Formula

The following equation is used to calculate the Kettle Efficiency.

E = V*I*T / (m*c*ΔT) *100

  • Where E is the efficiency of the kettle (%)
  • V is the voltage (volts)
  • I is the current (amps)
  • T is the time (seconds)
  • m is the mass of water (g)
  • c is the specific heat capacity of water (4.184 J/g*C)
  • ΔT is the change in temperature (C)

What is a Kettle Efficiency?


Kettle efficiency refers to the ratio between the amount of steam generated when boiling water in a kettle and the amount of heat energy used. Kettle efficiency is expressed as a percentage.

The higher the percentage, the more efficient the kettle. A kettle’s efficiency may be affected by its lid, shape, material and more. Kettle manufacturers often state their own kettle efficiency on product packaging or online.

A kettle is a heat transfer device to boil water. It is also called a boiler, an urn or a hot water urn. The purpose of the heat transfer device is to boil water to make it ready for use in different processes.

To calculate kettle efficiency, you must know how much energy is required to boil the water. This varies by volume of water and atmospheric pressure.

The U.S. Department of Energy recommends using 454 joules (the equivalent of 100 kilowatt hours) to boil 1 liter of water at sea level at 101 degrees Celsius (atmospheric pressure averages 14.7 pounds per square inch). This amount is known as the “specific energy.” Specific energy is multiplied by 100 to determine kwh efficiency ratings for kettles.

For example, a 1-liter kettle uses 454 x 100 = 45,400 joules to boil 1 liter of water. To calculate kwh efficiency at sea level, divide 45,400 by 454 = 90 percent.