Boiler Size Calculator
UK/Europe-focused boiler sizing estimate based on radiators, age/insulation, and hot water demand (for combi).
Units
Boiler type
Insulation quality
Number of radiators
8radiators
Number of bathrooms
1bathrooms
Hot water add-on applies to Combi only: 1 bath = +3kW, 2 bath = +8kW, 3+ bath = +11kW.
Insulation upgrades
Deductions: loft −0.5kW, cavity −0.8kW, both −1.2kW.