Costs and pricing
Hot water running cost calculator
What heating your water actually costs over a year, from your usage and your energy rate.
Per kilowatt-hour. Total bill divided by kWh used gives your real rate.
Electricity used per year
3,816 kWh
Add your rate above to see what that costs.
- Per month
- 318 kWh
An estimate based on the figures you entered. Your actual costs will differ.
The invisible quarter of your electricity bill
Heating water is usually one of the two largest electrical loads in a home, and unlike lighting or appliances it is completely invisible — there is nothing to switch off, and nothing that looks like it is costing money.
Putting a number on it is mostly useful for perspective. Once you know what it costs a year, decisions about insulation, fixing a hot tap that drips, or what a heat pump water heater would save stop being guesswork.
Where the volume comes from
Showers dominate. A standard showerhead uses roughly two gallons a minute, so a ten-minute shower is around twenty gallons — most of a single person's daily use in one go. Baths, dishwashing and laundry make up most of the rest.
The presets above are a household-size guide, not a measurement. If you want a real figure, the number of showers a day multiplied by their length and your showerhead's flow rate will get you close.
Why there is no temperature setting on this page
Almost every other hot water calculator invites you to enter your tank temperature and then shows you what you would save by lowering it. This one deliberately does not, and it never will.
Tank temperature is a safety setting with danger at both ends. Too low and the tank can grow bacteria, including legionella. Too high and the water scalds — a particular risk with children and older people, and fast enough to injure before anyone can react.
That is a plumber's decision about a specific system in a specific household, not a slider on a savings calculator. The figures here use a fixed assumption about temperature rise purely to convert gallons into kilowatt-hours, and it is not something to adjust.
What actually reduces the cost safely
All of these reduce how much hot water you use, which is the lever that carries no risk. None of them involve touching the thermostat.
- Fixing a dripping hot tap — you are paying to heat every drop
- A lower-flow showerhead, or shorter showers
- Insulating the first few feet of pipe leaving the tank
- Washing laundry cold where it makes no practical difference
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