How much electricity does an electric water heater use per month?

A typical electric tank water heater for a family of 4 using 60 gallons per day uses about 310 kWh per month. At $0.15/kWh this costs about $46/month. A heat pump water heater does the same job for about 80 kWh/month, saving $34/month.

How many solar panels does it take to power a water heater?

A heat pump water heater using 80 kWh/month needs about 2-3 solar panels (400W each) to cover its electricity use. A conventional electric tank using 310 kWh/month would need 8-10 panels. The heat pump water heater is the more efficient pairing with solar.

Hot Water Energy Calculator

Calculate how much energy your water heater uses — and compare gas tank, electric tank, tankless, and heat pump options.

Hot water usage

Hot water usage?

gal/day

Water heater type?

Inlet water temp?

°F

Hot water setpoint?

°F

Electricity rate?

$/kWh

Tank — Natural gas

$1,820.49/month

Daily energy11.86 kWh

Daily cost$60.68

Annual cost$21,846/yr

Solar to offset~8 panels

Link copied to clipboard

How to Use This Calculator

Set your daily hot water usage

The US average is about 20 gallons per person per day for all domestic uses (showers, bathtubs, dishwasher, laundry, faucets). A family of 4 typically uses 50-80 gallons per day. A short shower uses ~10 gallons; a bath uses ~35-40 gallons; dishwasher cycle ~6 gallons; clothes washer ~13 gallons per load.

Select your water heater type

The biggest factor in hot water energy cost is your water heater technology. A heat pump water heater (UEF ~3.5) uses 3-4 times less electricity than an electric resistance tank (UEF ~0.92). A gas tankless heater (EF ~0.96) is more efficient than a gas tank (EF ~0.67) because there's no standby heat loss. The calculator uses published efficiency factors (EF/UEF) for each type.

Set temperatures

Enter your cold water inlet temperature (groundwater temperature for your region — typically 45-55°F in the northern US, 65-75°F in the South) and your hot water setpoint (120°F is standard). A larger temperature rise requires more energy; switching from 140°F to 120°F setpoint saves 6-10% on water heating energy.

The Formula

Daily BTU needed = Gallons/day × 8.34 lb/gal × (Outlet °F − Inlet °F) Daily BTU input = Daily BTU needed ÷ Efficiency (EF/UEF) Daily kWh (electric) = Daily BTU input ÷ 3,412 BTU/kWh Daily cost (electric) = Daily kWh × electricity rate Monthly cost = Daily cost × 30 days Annual cost = Monthly cost × 12

The 8.34 lb/gal is the weight of water. Heating 1 pound of water by 1°F requires 1 BTU (definition of BTU). So heating 1 gallon from 55°F to 120°F requires 8.34 × 65 = 542 BTU.

Gas costs are estimated at $1.50/therm (1 therm = 100,000 BTU). Electric costs use your entered rate. Heat pump water heater cost = electric tank cost ÷ 3.5 (the approximate UEF).

Example

Family of 4 — comparing tank electric vs heat pump water heater

A family uses 60 gallons per day. Cold water enters at 55°F; hot water is set to 120°F. They pay $0.15/kWh for electricity.

Daily usage60 gal/day

Temperature rise65°F (55°F to 120°F)

Daily BTU needed32,526 BTU

Electric tank (UEF 0.92)

Daily kWh10.4 kWh

Monthly cost$46.80/month

Annual cost$562/year

Heat pump water heater (UEF 3.5)

Daily kWh2.72 kWh

Monthly cost$12.26/month

Annual cost$147/year

Annual savings vs tank$415/year

Switching to a heat pump water heater saves $415 per year. With an installed cost of ~$1,200 (after the 30% IRA tax credit on a ~$1,800 unit), the payback period is under 3 years. The unit will then save $415/year for its 10-15 year lifespan.

FAQ

How much of a home's energy bill is water heating? ▼

Water heating accounts for 14-18% of a typical US home's energy bill, making it the second-largest energy expense after space heating and cooling. For households with an electric water heater, it's often 15-20% of the electricity bill. Upgrading to a heat pump water heater or tankless gas heater is one of the highest-ROI home efficiency investments available.

Can solar panels power a water heater? ▼

Yes. An electric or heat pump water heater can be powered by solar panels through your home's electrical system. A heat pump water heater using 3 kWh/day needs about 2 solar panels (400W) to cover its energy use. Some homeowners install "solar water diverters" that automatically redirect excess solar production to an immersion heater element, eliminating the need to export that energy to the grid. Solar thermal (evacuated tube or flat plate collectors) is another option specifically designed for water heating, with no electricity conversion losses.

What temperature should I set my water heater? ▼

120°F (49°C) is the EPA and DOE recommended setting for most homes — it's hot enough to prevent Legionella bacteria growth, reduces scalding risk, and minimizes standby heat loss. Lowering from 140°F to 120°F saves 6-10% on water heating energy. If you have a tankless or heat pump unit with on-demand heating, you can sometimes set to 115°F safely. For homes with immune-compromised residents, stay at 120°F minimum.

Is a heat pump water heater worth it? ▼

For most electric water heater owners: yes. Heat pump water heaters (HPWH) use 3-4x less electricity and typically pay back their cost premium in 3-5 years. The IRA provides a 30% federal tax credit (up to $2,000) for qualifying models. They work best in unconditioned spaces like garages or basements where they can extract heat from ambient air. In a conditioned living space, they shift some heating load to your HVAC system — which is fine in summer (free cooling), but in winter in cold climates, this can offset some savings.