Water Heater Energy Cost Calculator

How to calculate water heater energy costs?

To accurately estimate the energy consumption of a water heater, you must consider the volume of water used daily, the temperature rise (the difference between incoming cold water and the thermostat setting), and the Energy Factor (EF), which represents the overall efficiency of the appliance.

Energy = (Gallons × 8.33 × Temp Rise) / Energy Factor

Using the calculator: an example

Imagine a typical household that consumes 50 gallons of hot water daily. If the incoming cold water is 55°F and the tank is set to 120°F (resulting in a 65°F temperature rise), with a water heater Energy Factor (EF) of 0.90, we can determine the daily cost by following these steps:

Step-by-step calculation:

1. Find total BTUs: Multiply 50 gallons × 8.33 (weight of water) × 65°F rise to get 27,072.5 BTUs.
2. Adjust for efficiency: Divide the BTUs by the 0.90 EF to find the total energy input needed (30,080 BTUs).
3. Convert to units: For electric heaters, divide BTUs by 3,412 to get 8.82 kWh; for gas, divide by 100,000 to get 0.30 Therms.
4. Calculate cost: Multiply the units used by your local utility rate (e.g., 8.82 kWh × $0.15/kWh = $1.32 per day).

Frequently Asked Questions

What is an Energy Factor (EF)?

The Energy Factor (EF) is a metric that measures the overall energy efficiency of a water heater. A higher EF indicates a more efficient unit with less energy loss during the heating process and through the tank walls.

How can I lower my heating costs?

You can reduce costs by lowering your thermostat to 120°F, installing low-flow faucets, insulating your hot water pipes, or upgrading to a high-efficiency Heat Pump Water Heater.

Why does my geographic location matter?

Location determines your groundwater temperature. In colder climates, the heater must work harder to raise the water temperature from 40°F compared to a warmer climate where incoming water may be 70°F.