Short answer: for most apartments the best-value heat pump is an inverter air conditioner, that is an air-to-air heat pump in each living room. For 70 m², three Nordic models cost about 1 475 €, and the seasonal electricity bill is about 188 €. An air-to-water heat pump starts at 3 196 € for the unit alone and makes sense in three specific cases, described below.
Three options for an apartment
| An air conditioner in each room | Multi-split | Air-to-water heat pump | |
|---|---|---|---|
| Outdoor units | one per room | one for 2–5 rooms | one (monobloc) |
| Heats | the air | the air | water in radiators or underfloor heating |
| Hot water | no | no | yes, with a cylinder |
| Cooling | yes | yes | limited |
| Equipment for 70 m² | about 1 475 € | more than separate splits | from 3 196 € + installation |
| Renovation in the flat | no | no | yes, if there is no water heating system |
All three are heat pumps. The only difference is what they pass the heat to. Why an air conditioner is a heat pump is explained in air-to-air heat pump.
How much capacity you need
An apartment loses less heat than a house of the same size, because it has neighbours above, below and on the sides. A guide for an insulated or renovated block is 55 W/m². For a corner, top or ground floor without insulation, count on 80–100 W/m².
| Area | Capacity needed (55 W/m²) | Uninsulated, corner (90 W/m²) |
|---|---|---|
| 50 m² | 2.8 kW | 4.5 kW |
| 70 m² | 3.9 kW | 6.3 kW |
| 90 m² | 5.0 kW | 8.1 kW |
| 120 m² (maisonette) | 6.6 kW | 10.8 kW |
With air-to-water there is a catch: the smallest units in our catalogue are 4.3–6 kW. For an insulated apartment under 70 m², even these have spare capacity. That is why air conditioners usually match small homes more precisely. Capacity by room can be worked out with the how many BTU do I need calculator.
The electricity bill by floor area
Calculated for Varna and the Black Sea coast: 1 500 equivalent full-load hours per season, an insulated home (55 W/m²), electricity at 0.15 €/kWh. This is the same basis as in how much electricity a heat pump uses, so the figures are comparable.
| Area | Air conditioners (SCOP 4.6) |
Air-to-water + underfloor (SCOP 4.0) |
Air-to-water + radiators (SCOP 3.0) |
Convectors (1.0) |
|---|---|---|---|---|
| 50 m² | 135 € | 155 € | 206 € | 619 € |
| 70 m² | 188 € | 217 € | 289 € | 866 € |
| 90 m² | 242 € | 278 € | 371 € | 1 114 € |
| 120 m² | 323 € | 371 € | 495 € | 1 485 € |
In an apartment, air conditioners win both on equipment price and on the electricity bill. The reason is that they give heat directly to the air, without heating water to 35–55 °C. The hotter the water, the lower the heat pump’s coefficient. Why radiators bring SCOP down to about 3.0 is explained in heating with a heat pump and radiators.
Over ten seasons the gap grows. Three air conditioners come to about 3 355 € including electricity, while air-to-water with radiators comes to about 6 086 €, and that is before any water pipework. What air-to-water keeps in its favour is hot water, which air conditioners do not make. For a house where hot water weighs more, the calculation is in heat pump or air conditioners for a house.
But air conditioners heat only the rooms that have an indoor unit. The hallway and bathroom stay cooler if the doors are closed.
Option 1: an air conditioner in each room
For a typical 70 m² apartment with two bedrooms and a living room:
- 2 × Nippon NPC 09 T-PRO NORDIC for the bedrooms — 475 € each, heating class A++, heats down to −25 °C;
- 1 × Nippon NPC 12 T-PRO NORDIC for the living room — 525 €, SCOP 4.7, down to −25 °C.
In total 1 475 € for the equipment. Installation takes about a day per unit and needs no renovation. If you want a higher class and more reserve for cold spells, look at Gree Amber GWH09YD — 996 €, A+++ for heating, down to −30 °C. More models are in the ranking of the best air conditioners for heating.
Option 2: multi-split
One outdoor unit serves two to five indoor units. It suits you when there is room for only one unit on the facade or balcony, or the owners’ association does not allow more. The equipment usually costs more than separate splits, and if the outdoor unit fails, every room stops. Pros and limits are covered in what is a multi-split system, and ready sets with prices in air conditioner with two indoor units.
Option 3: air-to-water heat pump
In an apartment it makes sense in three cases:
- You have your own water heating system. For example, radiators or underfloor heating fed by a gas or electric boiler. The heat pump replaces the boiler without touching the radiators.
- You want underfloor heating. With low water temperature the heat pump works at its highest coefficient, and the heat is even and silent.
- A large family that uses a lot of hot water. The heat pump heats bathroom water with about three times less electricity than an ordinary electric water heater.
The models in stock best suited to an apartment are small and single-phase, so they do not need a three-phase supply:
| Model | Capacity | Outdoor noise | Price |
|---|---|---|---|
| Daikin Altherma EHBX04D6V + ERGA04DV, split | 4.3 kW | 44 dB(A) | 4 607 € |
| LG Therma V Monobloc HM051MRS | 5.5 kW | 54 dB(A) | 4 364 € |
| Gree Versati IV monobloc GRS-CQ6Pd | 6 kW | 52 dB(A) | 3 247 € |
| AUX ACHP-H08/4R3HA | 8.4 kW | 45 dB(A) | 3 196 € |
| Atlantic LORIA DUO 6003, with a 190 l cylinder | 3 kW | — | 5 368 € |
Atlantic LORIA DUO is the only model with a built-in cylinder, so you do not need a separate place for a hot water tank. Daikin is the quietest. AUX and Gree are the most affordable, but for an insulated apartment up to 70 m² their capacity is well above what is needed.
What to check in the building before you buy
- A place for the outdoor unit. Balcony, facade or roof. An air-to-water monobloc is larger and heavier than an air conditioner’s outdoor unit and needs a solid base.
- The owners’ association. In many buildings changes to the facade require consent. Check the house rules before buying, not after.
- Noise for the neighbours. Compare outdoor unit noise in dB(A). A 10 dB difference is perceived as twice as loud.
- The power supply. The models in the table are single-phase, but check that your fuse board copes together with a water heater and an oven.
- Condensate drainage. In winter the outdoor unit releases water when it defrosts. It must not drip onto the balcony of the neighbour below.
What to do now
If you have no water heating system, start with air conditioners: they are cheaper both to buy and to run. If you have radiators or underfloor heating and a boiler to replace, an air-to-water heat pump is worth calculating. What a complete system for a house costs is covered in heat pump for a house — price.
All models are in air conditioners for heating and heat pumps. We install in Varna and along the Black Sea coast. On a site visit we will see where the outdoor unit can go and give you a quote including installation. The site visit is free.
Heat pump installation in Varna: free site visit
Frequently asked questions
Does an air-to-water heat pump pay off in an apartment?
Rarely, if there is no water heating system. For 70 m², air conditioners cost about 1 475 € and use about 188 € of electricity per season. An air-to-water heat pump with radiators costs from 3 196 € for the unit alone and uses about 289 €.
What heat pump for a 60–70 m² apartment?
An insulated apartment needs about 3.5–4 kW. With air conditioners, that is two 9 000 BTU units and one 12 000 BTU unit. With air-to-water, the smallest 4.3–6 kW models are more than enough.
How much electricity does a heat pump use in an apartment?
In Varna, for an insulated 70 m² apartment: about 188 € per season with air conditioners, about 217 € with air-to-water and underfloor heating, and about 289 € with air-to-water and radiators. For comparison, convectors cost about 866 €.
Do I need permission from the owners’ association?
It depends on the building and where the outdoor unit goes. In many blocks changes to the facade require consent. Check your association’s rules before buying.
Can a heat pump be installed on a balcony?
Yes, if the base can carry the weight, there is airflow around the unit and condensate is drained. An air-to-water monobloc is heavier and larger than an air conditioner’s outdoor unit, so the spot is checked on a site visit.
Is a heat pump noisy for the neighbours?
The apartment-sized models in our catalogue are between 44 and 54 dB(A) at the outdoor unit. The quietest is the Daikin Altherma 4.3 kW at 44 dB(A).
Does an air conditioner make hot water?
No. If you also want hot water from a heat pump, choose air-to-water with a cylinder, for example Atlantic LORIA DUO with a built-in 190-litre cylinder.
