When to use this calculator
Estimate energy spending for a water-temperature increase under a stated efficiency. Assumes 1 kg/L water and constant heat capacity, with no phase change; storage losses are excluded.
Explore the electricity use & bills calculators for other questions in this topic. For a related calculation, use the Carbon Emissions Calculator: Estimate emissions from activity multiplied by a chosen emission factor.
PUTTING IT INTO PRACTICE
Water Heating Cost: 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 (K) | 40 |
| Heating efficiency (%) | 100 |
| Energy price per kWh | 0.3 |
| Result | 1.394667 currency units |
- Check the input labels and enter the example values above.
- Apply the relationship: Cost ≈ litres × 4.184 × temperature rise/3600/efficiency × price.
- The result is 1.394667 currency units, rounded for display.
How to interpret your result
Assumes 1 kg/L water and constant heat capacity, with no phase change; storage losses are excluded.
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.
When is the water heating cost calculator useful?
Estimate energy spending for a water-temperature increase under a stated efficiency. Assumes 1 kg/L water and constant heat capacity, with no phase change; storage losses are excluded.
How do I use the water heating cost calculator?
Enter water volume (litres), temperature rise (k), heating efficiency (%), energy price per kwh. The result updates automatically. Use the units shown beside each input; the example values illustrate the method.
Which formula does this calculator use?
Cost ≈ litres × 4.184 × temperature rise/3600/efficiency × price.
What should I check before using the result?
Assumes 1 kg/L water and constant heat capacity, with no phase change; storage losses are excluded.
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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