Calculate your cost
Start with the example below, then replace the wattage, daily runtime, and rate with the numbers for your electric water heater.
This setup uses about 405 kWh in a 30-day month.
Please enter valid values within the ranges shown.
| Schedule | Hours/day | Cost/month |
|---|---|---|
| Half runtime | 1.5 | $38.13 |
| Page example | 3 | $76.26 |
| Longer runtime | 4.5 | $114.39 |
Same 4,500-watt input and 18.83¢/kWh rate; only runtime changes.
Formula for the page example
4.5 kW × 3 hr × $0.1883 = $2.54 per day
Convert watts to kilowatts, multiply by the active hours used each day, then multiply by the electricity price in dollars per kWh. Multiply the daily result by 30 for the monthly estimate shown above.
How to read this estimate
A conventional electric tank heater cycles a high-power element to warm incoming water and make up for standby heat loss. Most of its cost follows household hot-water use, not the number of hours it remains connected.
Use this as a baseline until you can check the label or measure the electric water heater directly. Model, settings, condition, climate, and household routine can all change the result.
What changes the cost?
- 01
Tank size, element wattage, insulation, and thermostat setting
- 02
Number and length of showers and other hot-water draws
- 03
Incoming water temperature and standby heat loss
Ways to spend less
- Repair hot-water leaks and use efficient showerheads.
- Choose a safe, moderate temperature setting.
- Insulate accessible hot-water pipes where appropriate.