Hot water cost calculator
An estimate of what you pay each month to heat water for showers and the kitchen.
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Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Enter hot water per day, cold water temperature, hot water temperature, heater efficiency, days in month and price per kwh.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
Daily kWh = liters per day × 4.186 × temperature rise ÷ 3600 ÷ efficiency. Monthly = daily × days. Cost = energy × price.
Example
Inputs: Hot water per day = 150 L, Cold water temperature = 25 °C, Hot water temperature = 50 °C, Heater efficiency = 90 %, Days in month = 30. Result: Monthly cost: 26.16; Daily energy: 4.84 kWh; Monthly energy: 145.3 kWh.
Limits and caveats
- It assumes water specific heat of 4.186 kJ per kg per °C and density of 1 kg per liter.
- Tank and pipe standby losses are not included and can be significant in older heaters.
- It uses a flat electricity price with no tiers.
Questions about this tool
How much hot water does a household use?
It varies a lot with family size and shower length, so estimate your own use and enter it.
How can I cut water heating cost?
Lower the set temperature a little, use a low-flow shower head and insulate pipes; every degree less cuts energy directly.
Why does the cold water temperature matter?
Energy is proportional to the temperature rise; in Gulf summers the supply is warm, so less energy is needed.