What size heat pump for a 100 m² house?
A 100 m² house insulated after 2000 needs about 5.8 kW in zone III including hot water for four people: a 6 kW class heat pump. A new house built to WT 2021 needs about 3.6 kW and an uninsulated one about 11.1 kW. The calculator starts at 100 m², change the insulation and zone.
Example: 100 m² house, insulated, zone III
Heat pump output needed at −20°C: about 5.8 kW
heating about 5.3 kWhot water about 0.4 kW
Heat pump size for comparing quotes
6 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 5.8 kW at −20°C.
Electricity for heating and hot water
about 3,886 kWh a year, about 4,041 PLN
about 337 PLN a month on average
Prices from 11 October 2026, estimate
| Item | Value |
|---|---|
| Heat for space heating | 10,000 kWh/yr |
| Heat for hot water | 3,600 kWh/yr |
| Full-load hours | 1,871 h |
| House heat loss per degree | 0.13 kW/K |
| Heating load at −20°C | 5.3 kW |
| Hot water allowance | 0.4 kW |
| Design load | 5.8 kW |
| Heat pump size class | 6 kW class |
| Electricity per year | 3,886 kWh/yr |
| Electricity cost per year | 4,041 PLN |
Assumptions and formulaPrices from 11 October 2026
t = 3,118.9 × 24 h ÷ (20 - (−20)) = 1,871 h P = 10,000 kWh ÷ 1,871 h = 5.3 kW Pdhw = 4 people × 900 kWh ÷ 8760 h = 0.4 kW E = 13,600 kWh ÷ 3.5 = 3,886 kWh, cost = 3,886 kWh × 1.04 PLN = 4,041 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
Output for three insulation standards
Zone III (-20°C), hot water for four people. House insulated after 2000: about 5.3 kW for heating and about 5.8 kW with hot water, a 6 kW class. New house built to WT 2021: about 3.6 kW, less than the smallest common 4 kW heat pumps. Choose a model with a low minimum output so it does not run in short cycles in autumn.
An uninsulated house needs about 11.1 kW, a 12 kW class. With a backup heater and a bivalent temperature of, for example, -9°C a pump of about 8.2 kW (10 kW class) is enough, and the heater adds about 2.9 kW at -20°C.
Electricity use in a 100 m² house
A house insulated after 2000 with hot water for four people needs about 13,600 kWh of heat a year. A heat pump with SCOP 3.5 uses about 3,886 kWh of electricity for that, about 4,041 PLN a year or about 337 PLN a month on average. In a new house built to WT 2021 it is about 2,743 kWh and about 2,853 PLN.
Frequently asked questions
Is a 4 kW heat pump enough for a 100 m² house?
In a new house built to WT 2021, roughly yes: it needs about 3.6 kW at -20°C including hot water for four people. A house insulated after 2000 needs about 5.8 kW, so with a 4 kW pump the heater would run a lot in frost.
What does heating a 100 m² house with a heat pump cost?
In a house insulated after 2000 with hot water for four people, about 4,041 PLN a year at SCOP 3.5 and the calculator's electricity price, before fixed charges. That is about 3,886 kWh of electricity.