Enter the mass of the water (kg), the change in temperature (T), and the total energy input into water heater (J) into the calculator to determine the Water Heater Efficiency.

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## Water Heater Efficiency Formula

The following formula is used to calculate the Water Heater Efficiency.

**Ewh = m*C*dT / Q * 100**

- Where Ewh is the Water Heater Efficiency (%)
- m is the mass of the water (kg)
- C is the change in temperature (C)
- Q is the total energy input into water heater (J)
- C is the specific heat of water (4.186 J /kg-C)

## How to Calculate Water Heater Efficiency?

The following example problems outline how to calculate the Water Heater Efficiency.

**Example Problem #1**

- First, determine the mass of the water (kg). In this example, the mass of the water (kg) is given as 16 .
- Next, determine the change in temperature (C). For this problem, the change in temperature (C) is given as 20 .
- Next, determine the total energy input into water heater (J). In this case, the total energy input into water heater (J) is found to be 2200.
- Finally, calculate the Water Heater Efficiency using the formula above:

Ewh = m*C*dT / Q * 100

Inserting the values from above and solving yields:

Ewh = 16*4.186*20 / 2200 * 100 = 60.88 (%)

**Example Problem #2**

Using the same method as above, determine the variables required by the equation. For this example problem, these are provided as:

mass of the water (kg) = 24

change in temperature (C) = 30

total energy input into water heater (J) = 5000

Enter these given values yields:

Ewh = 24*4.186*30 / 5000 * 100 = 60.278** **(%)