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Boiler Size Estimator
Ctrl+D to bookmark this toolEstimate total heating load from property size and insulation level, then match to standard boiler outputs. Free, instant results.
Estimated boiler output
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Heating load
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DHW allowance
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Formula: Output (kW) = (Area × Rate / 1000) + DHW allowance
Indicative sizing only. Not a substitute for a full heat loss calculation per BS EN 12831. Oversizing factor not included.
Typical boiler sizing guide
Approximate output ranges for UK gas boilers. System and combi boilers may differ due to DHW demand.
| Property type | Floor area (m²) | Typical output (kW) | Notes |
|---|---|---|---|
| 1–2 bed flat | 40 – 65 | 12 – 18 | Combi often sufficient |
| 2–3 bed terrace | 65 – 90 | 18 – 24 | Combi or system |
| 3–4 bed semi | 90 – 130 | 24 – 32 | System with cylinder |
| 4–5 bed detached | 130 – 200 | 32 – 45 | System or regular boiler |
| Large detached | 200+ | 45+ | May need multiple boilers |
MEP Desk includes full property-level heat loss calculations, boiler sizing with margins, and links to real product data and project schedules.