How this calculator works
Estimate electric water-heating energy and cost from hot-water volume, temperature rise, efficiency, and electricity price.
Volume and temperature rise drive the load
Heating more water or starting with colder inlet water increases the required energy. The calculator converts the water mass and temperature rise into thermal energy, then divides by equipment efficiency.
- Use mixed hot-water volume, not total household water use.
- Inlet-water temperature varies by season and location.
- A tank can also lose heat while stored water waits to be used.
Tank and heat-pump models need different efficiency inputs
A conventional resistance tank is commonly modeled near 0.90 for a simplified operating estimate. A heat-pump water heater can deliver more heat than the electricity it consumes, so its effective value may be above 1.0. Use manufacturer or EnergyGuide information when available.
How to improve the estimate
Compare the result with measured circuit energy, an EnergyGuide annual kWh figure, or a utility interval-data pattern. Recirculation, standby losses, long pipe runs, leaks, and backup heating elements can materially change actual use.
Frequently asked questions
How many gallons of hot water does a household use?
It varies with household size, shower length, fixture flow, laundry, dishwashing, and behavior. A measured or audited value is better than a generic assumption.
Does this include tank standby loss?
The efficiency input can approximate it, but the tool does not model tank insulation and standby loss separately.
Can I model a heat-pump water heater?
Yes. Enter an effective efficiency or COP appropriate to the operating mode and conditions.
Use equipment documentation, your utility rate schedule, and measured data when they are available.