Heat Pump Sizing for 40 m² (431 sq ft) — UK & Temperate Maritime (-5°C Design, UK/IE/NZ)
Thermal heat loss calculation, recommended heat pump capacity (kW, BTU/h & HVAC Tons), SCOP efficiency, and annual electricity consumption.
Recommended Heat Pump2.7 kW9,213 BTU/h (0.77 Tons)
Annual Electricity Usage918 kWh/yrDelivers 3,762 kWh Heat (SCOP 4.1)
Savings vs Direct Electric2,844 kWh/yrSpecific Load: 52.2 W/m²
Electrical Circuit (230V)6 A BreakerPeak Compressor Input: 0.82 kW
Thermal & Electrical Specification Table (40 m² / 431 sq ft)
| Heated Floor Area | 40 m² (431 sq ft) |
| Climate Zone & Design Outdoor Temp | UK & Temperate Maritime (-5°C Design, UK/IE/NZ) |
| Building Insulation Envelope | Standard Double-Glazed Insulation (55 W/m² Base) (52.2 W/m² Peak) |
| Peak Space Heating Load | 2.09 kW Thermal |
| Recommended Heat Pump Output (Incl. DHW) | 2.7 kW (9,213 BTU/h · 0.77 Tons) |
| Seasonal Coefficient of Performance (SCOP) | 4.1 (340%–450% Seasonal Efficiency) |
| Annual Heat Demand vs Electricity Consumed | 3,762 kWh Heat → 918 kWh Electricity |
Frequently Asked Questions
What kW size heat pump do I need for a 40 m² (431 sq ft) house?
For a 40 m² (431 sq ft) building with Standard Double-Glazed Insulation (55 W/m² Base) in UK & Temperate Maritime (-5°C Design, UK/IE/NZ), the peak space heating load is 2.09 kW (52.2 W/m²). Including domestic hot water allowance, a 2.7 kW (9,213 BTU/h / 0.77 Ton) heat pump is recommended.
How many kWh of electricity does a 2.7 kW heat pump use per year?
With a Seasonal Coefficient of Performance (SCOP) of 4.1 over 1800 full-load equivalent heating hours, the heat pump consumes approximately 918 kWh of electricity per year to deliver 3,762 kWh of heat — saving 2,844 kWh/year compared to direct electric radiators.
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