When to use this calculator
Estimate steady heat transfer through an envelope area using an overall U-value. Steady conduction estimate; ventilation, infiltration, solar gains and thermal storage are excluded.
Explore the electricity use & bills calculators for other questions in this topic. For a related calculation, use the Heat Pump Electricity Calculator: Estimate heat-pump electricity from delivered heat and an assumed COP.
PUTTING IT INTO PRACTICE
Heat Loss From U Value: 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 |
|---|---|
| Overall U-value (W/m²·K) | 0.4 |
| Area (m²) | 100 |
| Temperature difference (K) | 20 |
| Result | 800 W |
- Check the input labels and enter the example values above.
- Apply the relationship: Steady heat loss = U-value × area × temperature difference.
- The result is 800 W, rounded for display.
How to interpret your result
Steady conduction estimate; ventilation, infiltration, solar gains and thermal storage 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 heat loss from u value calculator useful?
Estimate steady heat transfer through an envelope area using an overall U-value. Steady conduction estimate; ventilation, infiltration, solar gains and thermal storage are excluded.
How do I use the heat loss from u value calculator?
Enter overall u-value (w/m²·k), area (m²), temperature difference (k). The result updates automatically. Use the units shown beside each input; the example values illustrate the method.
Which formula does this calculator use?
Steady heat loss = U-value × area × temperature difference.
What should I check before using the result?
Steady conduction estimate; ventilation, infiltration, solar gains and thermal storage 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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