What size heat pump for a 150 m² house?
A 150 m² house insulated after 2000 needs about 8.0 kW for heating in zone III and about 8.4 kW with hot water for four people: a 10 kW class heat pump. With a backup heater for the coldest days an 8 kW class is enough. The calculator starts at 150 m².
Example: 150 m² house, insulated, zone III
Heat pump output needed at −20°C: about 8.4 kW
heating about 8.0 kWhot water about 0.4 kW
Heat pump size for comparing quotes
10 kW class
- 4
- 6
- 8
- 10
- 12
- 14
- 16
The number in the model name is the output at one operating point, for example +7°C. In frost the pump gives less: the Buderus Logatherm WPLS8.2 delivers 9.34 kW at +7°C and 7.82 kW at -7°C. Check in the datasheet that the pump gives at least 8.4 kW at −20°C.
Electricity for heating and hot water
about 5,314 kWh a year, about 5,527 PLN
about 461 PLN a month on average
Prices from 11 October 2026, estimate
| Item | Value |
|---|---|
| Heat for space heating | 15,000 kWh/yr |
| Heat for hot water | 3,600 kWh/yr |
| Full-load hours | 1,871 h |
| House heat loss per degree | 0.20 kW/K |
| Heating load at −20°C | 8.0 kW |
| Hot water allowance | 0.4 kW |
| Design load | 8.4 kW |
| Heat pump size class | 10 kW class |
| Electricity per year | 5,314 kWh/yr |
| Electricity cost per year | 5,527 PLN |
Assumptions and formulaPrices from 11 October 2026
t = 3,118.9 × 24 h ÷ (20 - (−20)) = 1,871 h P = 15,000 kWh ÷ 1,871 h = 8.0 kW Pdhw = 4 people × 900 kWh ÷ 8760 h = 0.4 kW E = 18,600 kWh ÷ 3.5 = 5,314 kWh, cost = 5,314 kWh × 1.04 PLN = 5,527 PLN
The hot water allowance is the yearly hot water heat spread over the hours of the year: the minimum the pump must add to heating on a frosty day. Yearly use comes from SCOP. A datasheet SCOP (EN 14825) already includes the heater's work in a typical season, so switching the heater on does not change the kWh result here.
- Degree days per year
- 3,118.9Eurostat, heating degree days (nrg_chdd_m), Poland, 2015-2025 average
- Design temperature, zone III
- −20 °CPN-EN 12831 and PN-B-02403, via Gramwzielone.pl (25 Oct 2024)
- Room temperature
- 20 °C
- Hot water per person
- 900 kWh/yr
- Heat pump size classes
- 4-16 kW in 2 kW stepsrounded up, manufacturers' ranges differ
- Heat pump SCOP
- 3.5
- Electricity price
- 1.04 PLN/kWhURE G11 tariffs 2026 (PGE, Tauron, Enea, Energa), average with distribution
An estimate based on yearly heat demand. The output to buy is set by a designer or installer from a heat load calculation to PN-EN 12831. The cost excludes fixed charges.
How electricity, gas, pellet and coal prices have changed, month by month. Price history
Ready-made calculations
8 or 10 kW
For heating alone the house needs about 8.0 kW at -20°C, so without hot water an 8 kW class is enough. Hot water for four people adds about 0.4 kW, giving about 8.4 kW in total, a 10 kW class.
An 8 kW heat pump also works if a backup heater helps it in frost. At a bivalent temperature of, for example, -9°C the pump has to give about 6.2 kW and the heater about 2.2 kW at -20°C. In zone I the same house needs about 7.6 kW with hot water, in zone V about 9.2 kW.
New house and uninsulated house
A new 150 m² house built to WT 2021 needs about 5.2 kW with hot water, a 6 kW class. An uninsulated house needs about 16.4 kW, more than common domestic heat pumps. With a heater and a bivalent temperature of -9°C a pump of about 12.0 kW (12 kW class) plus a heater of about 4.4 kW is enough.
Electricity at SCOP 3.5: the house insulated after 2000 uses about 5,314 kWh a year, about 5,527 PLN. The uninsulated house needs about 33,600 kWh of heat, so about 9,600 kWh of electricity and about 9,984 PLN. With old radiators SCOP is often lower, so enter the datasheet value for 55°C in the calculator.
Frequently asked questions
8 kW or 10 kW heat pump for a 150 m² house?
For a house insulated after 2000 in zone III the result is about 8.4 kW with hot water for four people, so a 10 kW class. An 8 kW heat pump is enough if its datasheet shows at least that output at -20°C or if a backup heater helps it in frost.
What heat pump output does an old 150 m² house need?
Without insulation about 16.4 kW at -20°C including hot water for four people. After insulating to the standard of houses from the 2000s about 8.4 kW, roughly half.