Short answer: in an insulated 100–150 m² house, air conditioners heat for 269–404 € of electricity per season, while an air-to-water heat pump with underfloor heating costs 309–465 €. Add hot water for the bathroom and the bill flips: the heat pump with underfloor heating comes out 240–260 € cheaper per year. Air conditioners, on the other hand, cost less to buy and install. Why an air conditioner is also a heat pump is explained in air-to-air heat pump. Here we count the money for a whole house.
The question usually comes from people who are building or renovating a house. There are two routes. One is an air conditioner in every room, or a multi-split with a single outdoor unit on the facade; the other is an air-to-water heat pump that heats water for underfloor heating or radiators and, along with it, hot water for the bathroom. For a flat the numbers are different, and you will find them in heat pump for a flat.
Two scenarios for a 100–150 m² house
| Air conditioners or multi-split | Air-to-water heat pump | |
|---|---|---|
| What it heats | the air in rooms with an indoor unit | water for underfloor heating, radiators or fan coil units |
| Hallway, bathroom, staircase | only with a unit there or with doors open | the whole house |
| Hot water for the bathroom | no, the boiler stays | yes, with a cylinder on the heat pump |
| Cooling in summer | yes, in every room with a unit | only with underfloor heating or fan coil units |
| Installation | about a day, no renovation | hydraulic installation, after a site visit |
For the calculation we take two insulated houses. At 100 m² the heat needed per season is 8 250 kWh, at 150 m² it is 12 400 kWh. The basis is the same as in how much electricity a heat pump uses: 55 W per square metre, 1 500 hours per season in Varna and electricity at 0.15 €/kWh. For an old uninsulated house the figures there are almost double.
Equipment and installation cost
For the 100 m² house we assume a living room with kitchen of about 35 m² and three bedrooms. For the 150 m² house we assume a living room of 40–50 m² and four rooms. Room-by-room capacity follows how many BTU I need. Prices are from our stock as of 26.10.2026.
| Option | 100 m² house | 150 m² house |
|---|---|---|
| Separate air conditioners, Nordic series down to −25 °C | 1 950 € + installation 600 € = 2 550 € | 2 700 € + installation 780 € = 3 480 € |
| Multi-split with one outdoor unit | 2 400 € + installation 280 € = 2 680 € | 2 738 € + installation 330 € = 3 068 € |
| Air-to-water heat pump (unit only) | 3 196 €, 8.4 kW | 3 600 €, 10 kW |
The separate air conditioners are Nippon NPC T-PRO NORDIC: one 12000 BTU and three 9000 BTU units for the smaller house, one 18000 BTU and four 9000 BTU units for the larger one. Their heating SCOP is 4.6–4.7. In the catalogue 9000 BTU air conditioners start from 300 €, 12000 BTU – from 315 €, 18000 BTU – from 540 €. Standard installation of an air conditioner bought from us is 150 € up to 14 000 BTU and 180 € for 16 000–24 000 BTU (up to 3 m of piping).
The multi-split is AUX AM4-H36 with four indoor units and AM5-H42 with five. Its installation is 80 € for the outdoor unit and 50 € for each indoor unit, without the pipe runs to the rooms, which we measure on site. These outdoor units have SCOP 4.1 and heat down to −15 °C. For 150 m² the multi-split comes out cheaper than five Nordic air conditioners, but it uses more electricity and is weaker in frost. We have compared multi-split and separate units on price in air conditioner with two indoor units. All sets are in the multi-split systems category.
For the heat pump the table shows the unit only: AUX ACHP-H08 and ACHP-H10, both single-phase. The differences between a monobloc and a split, and which layout suits your house, are in the article monobloc or split heat pump. The rest depends on the house. We price installation, the hot water cylinder and the pipework after a free site visit, and if there is no water heating system, underfloor heating or radiators are a separate investment that often costs more than the unit itself.
The seasonal bill: heating
| Heating | 100 m² house | 150 m² house |
|---|---|---|
| Air conditioners, SCOP 4.6 | 1 793 kWh – 269 € | 2 696 kWh – 404 € |
| Multi-split, SCOP 4.1 | 2 012 kWh – 302 € | 3 024 kWh – 454 € |
| Heat pump + underfloor, SCOP 4.0 | 2 063 kWh – 309 € | 3 100 kWh – 465 € |
| Heat pump + radiators, SCOP 3.0 | 2 750 kWh – 413 € | 4 133 kWh – 620 € |
For heating alone, air conditioners win. They give heat straight to the air, while the heat pump first heats water to 35 °C for underfloor heating or to 50–55 °C for radiators. The hotter the water, the lower the coefficient. We explain this in detail in heat pump and radiators.
Hot water flips the bill
In a house with air conditioners, hot water stays on the electric boiler. For a family of four we assume 200 litres a day heated by 35 °C. That is about 2 970 kWh a year. The boiler takes it from the grid one to one, so 446 € a year. The heat pump heats the same water with about three times less electricity: 990 kWh, or 149 €.
| Heating + hot water per year | 100 m² house | 150 m² house |
|---|---|---|
| Air conditioners + electric boiler | 715 € | 850 € |
| Multi-split + electric boiler | 748 € | 900 € |
| Heat pump + underfloor | 458 € | 614 € |
| Heat pump + radiators | 562 € | 769 € |
With half the water, say for two people, the hot water line halves too: 223 € with a boiler against 74 € with a heat pump. With radiators the heat pump’s advantage shrinks to 80–150 € a year. And with a solar collector on the roof the water costs next to nothing, so air conditioners come out cheaper again.
The 10-year bill
Air conditioners cost less at the start, the heat pump spends less every year. So we count backwards: up to what amount the installation, pipework and cylinder of the heat pump keep it level with air conditioners over 10 seasons.
- 100 m² house with underfloor heating: up to about 1 900 €. With radiators: up to about 880 €.
- 150 m² house with underfloor heating: up to about 2 240 €. With radiators: up to about 690 €.
We count it like this: the price of the air conditioners with installation plus ten times the difference in the yearly bill, minus the price of the unit. A quote below the threshold means a cheaper heat pump over ten years. With radiators the threshold is low, because at SCOP 3.0 little of the yearly saving is left, especially in the larger house. Building underfloor heating or radiators, if the house has none, is not included.
The downsides of heating a house with air conditioners
An air conditioner heats the room it hangs in. The hallway, bathroom and staircase stay cooler unless the doors are open or there is a separate unit. The bathroom usually needs another heat source as well.
Warm air gathers under the ceiling and the ground floor can stay cool underfoot. Underfloor heating with a heat pump gives the opposite: heat from below, with no draught from a fan. In return, air conditioners cool fully in summer, and in Varna that counts.
When the air-to-water heat pump is the better choice
The heat pump wins when you heat the whole house and already have underfloor heating or radiators. It also wins when the family is large and uses a lot of hot water. Options by floor area and unit prices are in heat pump for a house – price, and all models in stock start from 3 196 € in the heat pumps category.
The heat pump distributes heat around the house through radiators, underfloor heating or fan coil units. Fan coils run on water from the heat pump like a radiator with a fan and can also cool. We often add a buffer tank to the system as well. We can supply and install both, the fan coil units and the buffer tank, priced after a site visit, because the price depends on the number of rooms and the installation. We describe the installation steps in heat pump installation in Varna.
The two routes often go together: the heat pump takes care of heating and hot water, and one or two air conditioners in the bedrooms cool in summer.
How to decide for your house
Answer four questions. Does the house have a water heating system? How many people live in it and how much hot water do they use? Do you want cooling in every room? What is the budget at the start?
If there is no water system, the budget is tight and you also need cooling, start with air conditioners. If there is underfloor heating or radiators and the family is large, the heat pump pays off. Book a free site visit in Varna and along the Black Sea coast: we will measure the house and work out both options with your numbers.
Frequently asked questions
Heat pump or air conditioner for a house: which is better value?
For heating alone, air conditioners use less: 269–404 € per season for an insulated 100–150 m² house against 309–465 € for a heat pump with underfloor heating. With hot water included, the heat pump with underfloor heating comes out 240–260 € cheaper per year.
Can a whole house be heated with air conditioners only?
Yes, if every living room has an indoor unit. The hallway and bathroom stay cooler, and hot water stays on the boiler.
How many air conditioners does a 100 m² house need?
Usually four: one 12000 BTU for the living room and three 9000 BTU for the bedrooms. With installation that is about 2 550 € for models that heat down to −25 °C.
Multi-split or separate air conditioners for a house?
For 100 m² separate air conditioners come out cheaper with installation; for 150 m² the AUX multi-split is cheaper than Nordic Nippon units. Separate units use less electricity (SCOP 4.6 against 4.1) and heat down to −25 °C. A multi-split makes sense when the facade can take only one outdoor unit.
How much does heat pump installation cost?
It depends on the house: whether there is a water heating system, a cylinder, a buffer tank and fan coil units. The site visit is free, and after it we give an exact quote.
