What does it cost to heat a house with a heat pump? A worked example for 150 m² near Poznań
We work out the annual cost of heating a 150 m² house near Poznań with a heat pump, with every assumption stated. We compare G11 and G12 tariffs, the effect of solar PV, and gas and coal.
"How much will I pay for electricity?" comes right after the question about installation price. Honestly, it depends on the house. Below I show how to work it out, with every assumption in the open. You can plug in your own numbers.
Since 1 January 2026 the household electricity price freeze no longer applies. So I am using market prices, not the rates from 2023-2025.
Assumptions
- House: 150 m², near Poznań, built in the last 10-15 years or a well-insulated older house, underfloor heating or large radiators.
- Annual heat demand: 15,000 kWh, including hot water for 4 people. For houses like this we see 14,000-16,000 kWh in practice, so I take the middle.
- Heat pump SCOP: 3.5 in a cautious case and 4.0 in a good case. SCOP is the ratio of heat delivered to the house to electricity used by the heat pump over the whole season.
- G11 electricity price: about PLN 1.10/kWh gross, including all variable charges. This is an assumption, not a price list. In 2026 the G11 price is roughly PLN 1.00-1.30/kWh, depending on supplier and network operator. The Poznań area is served by Enea.
- I leave out standing charges, which the house pays anyway.
The basic calculation
Electricity use = heat demand / SCOP.
- SCOP 3.5: 15,000 / 3.5 = about 4,290 kWh of electricity, so 4,290 × 1.1 = about PLN 4,700 a year.
- SCOP 4.0: 15,000 / 4.0 = 3,750 kWh of electricity, so 3,750 × 1.1 = about PLN 4,100 a year.
SCOP alone moves the result by about PLN 600 a year. That is why we talk so much about flow temperature.
The G12 tariff
On a two-zone tariff, electricity is cheaper at night and for part of the afternoon, and more expensive than G11 the rest of the time. A heat pump with a buffer tank, or with underfloor heating that stores heat well, can move a good share of its running time into the cheap hours. That is also when we schedule hot water heating.
Assumptions: PLN 0.75/kWh in the cheap zone, PLN 1.25/kWh in the expensive zone, 60% of consumption in the cheap zone. Average: 0.6 × 0.75 + 0.4 × 1.25 = PLN 0.95/kWh.
- SCOP 3.5: 4,290 kWh × 0.95 = about PLN 4,100 a year.
That is about PLN 600 less than on G11, but only if the system can really shift the heat pump's running time. Without a buffer and with radiators, the cheap-zone share is often below 60%.
Solar PV
A heat pump works hardest in winter and panels produce most in summer, so PV covers less of the heat pump's use than many clients expect. The heat pump uses power straight from the panels mainly for hot water in summer and for heating in spring and autumn. With a system of about 6-8 kWp, I assume self-consumption covers 20% of the heat pump's use.
- SCOP 3.5, G11: 4,290 × 0.8 = about 3,430 kWh from the grid, so 3,430 × 1.1 = about PLN 3,800 a year.
That saves about PLN 900 a year. I do not count net-billing for exported surplus here.
Comparison with gas and eco-pea coal
For the same 15,000 kWh of heat:
- Natural gas: condensing boiler with 90% seasonal efficiency, gas including distribution at about PLN 0.35/kWh (an assumption, without the standing charge for the connection). 15,000 / 0.9 = about 16,670 kWh of gas, so 16,670 × 0.35 = about PLN 5,800.
- Eco-pea coal: class 5 boiler with 75% seasonal efficiency, about 7.2 kWh per kilogram of fuel, PLN 1,600 per tonne (an assumption). 15,000 / 0.75 / 7.2 = about 2,780 kg, so 2.78 t × 1,600 = about PLN 4,400.
The table
Option | Consumption | Annual cost | Cost per kWh of heat |
|---|---|---|---|
Heat pump, G11, SCOP 3.5 | 4,290 kWh electricity | about PLN 4,700 | about PLN 0.31 |
Heat pump, G11, SCOP 4.0 | 3,750 kWh electricity | about PLN 4,100 | about PLN 0.28 |
Heat pump, G12, SCOP 3.5 | 4,290 kWh electricity | about PLN 4,100 | about PLN 0.27 |
Heat pump, G11, SCOP 3.5, PV 20% | 3,430 kWh from grid | about PLN 3,800 | about PLN 0.25 |
Condensing gas boiler | 16,670 kWh gas | about PLN 5,800 | about PLN 0.39 |
Eco-pea coal boiler | about 2.8 t | about PLN 4,400 | about PLN 0.30 |
On paper, eco-pea coal comes out close to a heat pump on G11. The table leaves out carrying sacks, cleaning the boiler, ash, fuel storage, and summer hot water, which coal-heated houses often heat with an immersion heater. Czyste Powietrze does not fund coal boilers either.
What moves the number
- Insulation. Heat demand is the biggest item in the calculation. A house that needs 25,000 kWh instead of 15,000 will pay proportionally more.
- Flow temperature. Every degree lower improves heat pump efficiency, roughly by 2-3%. Underfloor heating at 35 °C instead of radiators at 55 °C makes a SCOP difference you will see on the bill.
- Habits. 22 °C instead of 20 °C throughout the house usually means somewhere above 10% more heat. Turning the temperature down by several degrees at night does not usually help with a heat pump.
- Hot water. Heating water to 50-55 °C runs at lower efficiency than underfloor heating. A big family and a bath can add several hundred kWh of electricity a year.
- Settings. A badly set heating curve or a backup heater switching on for no reason can wipe out what good sizing saved.
When a heat pump costs more
Take a 1980s house, 150 m², uninsulated, with old radiators. Heat demand can reach 30,000 kWh, and SCOP at 55 °C can fall to about 3.0. Then: 30,000 / 3.0 × 1.1 = about PLN 11,000 a year. Gas in the same house: 30,000 / 0.9 × 0.35 = about PLN 11,700, and eco-pea coal about PLN 8,900. The heat pump's advantage almost disappears, and against coal it costs more.
In a house like that we first work out what insulation and a few larger radiators would achieve. Often a heat pump only makes financial sense after that work. Before asking anyone about costs, find out your fuel use over the last few seasons. That is where we start every conversation.
