Whole-Home Heat Loss Calculator
Estimate your home's room-by-room heat demand, radiator suitability, and indicative boiler or heat pump size using detailed property inputs.
Whole-Home Heat Loss Calculator
Estimate your home heat demand room by room, check likely radiator suitability, and understand whether lower-temperature heating could work in your property.
Start with the main inputs for a fast estimate, then open advanced options if you want a more tailored result.
1. Home and Climate Inputs
Location-Based Climate Defaults
Use your postcode to pull in climate conditions that affect estimated heat demand and flow temperatures.
Design temperature uses the published MCS reference station with a 0.6 C correction for each whole 100m above station altitude. Annual mean external temperature is used for floor transmission losses, and heating degree days follow the official MCS postcode-area table.
Advanced Assumptions
Advanced options include EPC lookup and bill-based calibration. Most homeowners can leave these alone unless they want a more tailored result.
4. Room-by-Room Heat Loss and Emitters
Emitter Inputs
Emitter Inputs
Emitter Inputs
5. Download Your Home Heating Summary
Create a customer-friendly PDF summary of the current heat-loss results, assumptions, and indicative system sizes.
Home Heating Summary
Run the calculator to see estimated heat demand, room-by-room suitability, and indicative system sizes.
Radiators and Flow Temperatures
Radiator suitability and flow-temperature guidance appear here after calculation.
Indicative System Sizes
Indicative equipment sizes will appear after the first run.
How This Estimate Is Built
Wall, roof, floor, window, and door heat loss are estimated from the areas and insulation values you enter.
Ventilation loss is estimated from air-change rate, room volume, and any MVHR efficiency entered.
Radiator output is adjusted from standard DT50 data to estimate how it performs at lower flow temperatures.
Annual demand is estimated from the total heat-loss coefficient, local heating degree days, and any bill or manual calibration inputs applied.