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

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)

To calculate the water heater efficiency, multiply the mass, specific heat, and change in temperature together, then divide by the total energy input into the water heat.

How to Calculate Water Heater Efficiency?

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

Example Problem #1

  1. First, determine the mass of the water (kg). In this example, the mass of the water (kg) is given as 16 .
  2. Next, determine the change in temperature (C). For this problem, the change in temperature (C) is given as 20 .
  3. 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.
  4. 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 (%)

FAQ

What factors can affect water heater efficiency?

Several factors can affect water heater efficiency, including the insulation of the water heater, the temperature setting, the age and condition of the water heater, and the initial temperature of the water. Additionally, the efficiency can be influenced by whether the water heater is gas or electric, as well as the overall maintenance and cleanliness of the system.

How can I improve my water heater’s efficiency?

Improving your water heater’s efficiency can be achieved by insulating the water heater and the pipes, lowering the temperature setting, performing regular maintenance to prevent sediment build-up, installing a timer to control its operation, and considering a tankless water heater for more efficient on-demand water heating. Additionally, ensuring that your water heater is the correct size for your household can prevent unnecessary energy consumption.

Is it worth upgrading to a more efficient water heater?

Upgrading to a more efficient water heater can be worth the investment, especially if your current water heater is old and less efficient. Newer models are designed to be much more energy-efficient, which can significantly reduce your energy bills. Additionally, some governments offer rebates or tax incentives for installing energy-efficient appliances, which can help offset the initial cost of the upgrade. Consider the long-term savings and environmental benefits when deciding whether to upgrade.