Heat Pump Sizing for 118 m² (1,270 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 Pump4.5 kW15,355 BTU/h (1.28 Tons)
Annual Electricity Usage1,721 kWh/yrDelivers 7,056 kWh Heat (SCOP 4.1)
Savings vs Direct Electric5,335 kWh/yrSpecific Load: 33.2 W/m²
Electrical Circuit (230V)10 A BreakerPeak Compressor Input: 1.36 kW
Thermal & Electrical Specification Table (118 m² / 1,270 sq ft)
| Heated Floor Area | 118 m² (1,270 sq ft) |
| Climate Zone & Design Outdoor Temp | UK & Temperate Maritime (-5°C Design, UK/IE/NZ) |
| Building Insulation Envelope | Modern / New Build Insulation (35 W/m² Base) (33.2 W/m² Peak) |
| Peak Space Heating Load | 3.92 kW Thermal |
| Recommended Heat Pump Output (Incl. DHW) | 4.5 kW (15,355 BTU/h · 1.28 Tons) |
| Seasonal Coefficient of Performance (SCOP) | 4.1 (340%–450% Seasonal Efficiency) |
| Annual Heat Demand vs Electricity Consumed | 7,056 kWh Heat → 1,721 kWh Electricity |
Frequently Asked Questions
What kW size heat pump do I need for a 118 m² (1270 sq ft) house?
For a 118 m² (1270 sq ft) building with Modern / New Build Insulation (35 W/m² Base) in UK & Temperate Maritime (-5°C Design, UK/IE/NZ), the peak space heating load is 3.92 kW (33.2 W/m²). Including domestic hot water allowance, a 4.5 kW (15,355 BTU/h / 1.28 Ton) heat pump is recommended.
How many kWh of electricity does a 4.5 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 1,721 kWh of electricity per year to deliver 7,056 kWh of heat — saving 5,335 kWh/year compared to direct electric radiators.
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