When to use this calculator
Estimate ideal energy required to raise water temperature. Assumes water density of 1 kg/L and heat capacity 4.184 kJ/(kg·K), without losses or boiling.
Explore the electricity use & bills calculators for other questions in this topic. For a related calculation, use the Heating Fuel Input Calculator: Estimate input fuel energy for a useful-heating demand.
PUTTING IT INTO PRACTICE
Heating Energy: a worked example
The values below are an illustrative example, not a recommendation. Replace them with measurements or assumptions that match your question.
| Input | Example value |
|---|---|
| Water volume (litres) | 100 |
| Temperature rise (°C) | 40 |
| Result | 4.648889 kWh |
- Check the input labels and enter the example values above.
- Apply the relationship: Energy (kWh) = litres × 4.184 × temperature rise ÷ 3600.
- The result is 4.648889 kWh, rounded for display.
How to interpret your result
Assumes water density of 1 kg/L and heat capacity 4.184 kJ/(kg·K), without losses or boiling.
Watts describe power and kilowatt-hours describe energy. Fixed charges do not vary directly with consumption. Devices with thermostats or cycling loads need measured average energy or realistic operating time.
Frequently asked questions
Can I multiply rated watts by 24 hours for every appliance?
Only if it actually draws that power continuously. Cycling and variable-power appliances require a better average-use estimate.
How do I use the heating energy calculator?
Enter water volume (litres), temperature rise (°c). The result updates automatically. Use the units shown beside each input; the example values illustrate the method.
Which formula does this calculator use?
Energy (kWh) = litres × 4.184 × temperature rise ÷ 3600.
What should I check before using the result?
Assumes water density of 1 kg/L and heat capacity 4.184 kJ/(kg·K), without losses or boiling.
How are results rounded?
Scalar numbers display up to six decimal places, with scientific notation for very large or small values. Text, fraction, date and schedule outputs use the format described on the tool. Intermediate calculations use JavaScript floating-point arithmetic. Keep sensible precision for your measurements.
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