Boiler Size Calculator
Rough boiler output in kW for a home from floor area, insulation and hot water demand.
Compare Your Options And Get Clear Answers
Rough boiler output in kW for a home from floor area, insulation and hot water demand.
Boiler Size Estimator
Enter your numbers below for an instant estimate.
How It Works
Key concepts behind this calculator
Enter Values
Fill in each field with your own numbers.
Calculate
Results update as you change the inputs.
Review
Read the breakdown and the explanation.
Adjust
Change values to compare scenarios.
Boiler Quick Guide
Typical values for reference.
| Area m2 | Insulation | Bathrooms | kW |
|---|---|---|---|
| 60 | 2 | 1 | 3.6 kW |
| 110 | 2 | 2 | 8.6 kW |
| 160 | 2 | 3 | 15.6 kW |
| 220 | 2 | 4 | 21.2 kW |
| Rule of Thumb | Check inputs | Use as a guide | Round sensibly |
Boiler Size Calculator FAQ
Answers to common questions about this calculator.
Space heating is often 6-12 kW, but combi boilers are rated 24-30 kW mainly for instant hot water. A heat loss survey gives the right size.
No, oversizing reduces efficiency.
kW = area x W/m2 for the insulation level + hot water allowance.
It is an estimate based on the inputs you enter. Check real quotes, labels or official guidance for important decisions.