Water heater
How much electricity does a water heater use?
3,500–4,500 W element · 300–500 kWh/month · $50–$85 per month
A tank water heater holds 150–300 litres at 50–60°C all day. The element is typically 3,500–4,500 W and runs 2–4 hours a day in total, which adds up to 300–500 kWh a month — often the largest line item on an all-electric bill.
Where the energy goes
- Heating new water: the majority, and unavoidable for the hot water you actually use
- Standby loss: 10–20% in a typical tank, radiating heat through the walls 24 hours a day
- Distribution loss: hot water cooling in the pipes between heater and tap
Cheapest fixes, in order
- Turn the thermostat down to 55°C. Every 10°C reduction saves 3–5%, and 55°C is still hot enough for a shower.
- Insulate the tank and the first two metres of pipe. Cheap, and cuts standby loss noticeably.
- Fix dripping hot taps. A hot tap dripping once a second wastes thousands of litres of heated water a year.
- Shorter showers. A ten-minute shower uses about 100 litres; halving it is the single biggest reduction available.
Heat pump water heaters
A heat pump water heater moves 2–3 kWh of heat per kWh of electricity instead of one. It costs two to three times as much up front and needs a cool space to draw from, but it typically halves the running cost — the payback is usually three to five years.
Frequently asked questions
How many watts does a water heater use?
3,500–4,500 W element. The figure on the rating label is the maximum draw; actual use varies with settings, age and usage pattern.
How much does it cost to run a water heater per month?
With the defaults above it comes to the monthly figure shown in the calculator. At 16.5¢/kWh — the US residential average — that is a realistic middle estimate. Your own bill may be 30% lower or higher depending on state.
Is it cheaper to run a water heater at night?
Only if your utility offers a time-of-use plan and you avoid the 4pm–9pm peak window. On a flat-rate plan, the time of day makes no difference to the total.
Does the calculator account for real-world duty cycles?
Not automatically — you enter the effective hours yourself. For compressing appliances like refrigerators and AC units, enter the running watts and roughly the proportion of time the compressor is on, which is usually 30–50%.
Will a newer water heater actually save money?
Compare the kWh figure in the calculator against an Energy Star model's stated annual use. If the difference is a few hundred kWh a year, the payback on a replacement is usually long; if it is over 500 kWh, it is worth pricing out.