Installing an air source heat pump in a flat: step by step

Air source heat pumps are an efficient and sustainable solution that can be installed in flats, provided requirements such as space for the outdoor unit, community permits, and suitable radiators are met. Installation involves a preliminary survey, system selection, equipment assembly, and configuration for heating and cooling, with costs ranging between €8,500 and €16,000, depending on size and complexity.

Before deciding, it is worth assessing insulation, electrical power capacity, regulations, and potential subsidies to reduce the initial investment.

Can you install an air source heat pump in a flat?

Yes, you can install an air source heat pump in a flat, provided certain technical and regulatory requirements are met. The key is having space for the outdoor unit (terrace, balcony, patio, or roof) and for the indoor module (hydrokit and hot water cylinder). Furthermore, you need an adequate electrical installation and, in many cases, permission from the Community of Owners if the work affects common areas such as facades or rooftops.

Advantages of installing an air source heat pump in a flat

• Energy efficiency: the system harnesses energy from the air to generate heat, making it one of the most efficient technologies on the market. For every electrical kWh consumed, it produces between 3 and 4 kWh of thermal energy, reducing consumption by up to 70% compared to traditional systems like gas or oil boilers. This translates to lower costs and higher performance.
• Financial savings: although the initial investment is higher than other systems, the monthly savings on heating and domestic hot water pay off in the medium term. In flats with intensive usage, the system can pay for itself in a few years, especially if combined with specific electricity tariffs and good insulation.
• Sustainability: aerothermal energy uses a renewable source: the air. This reduces CO₂ emissions and contributes to the decarbonisation of your home, aligning with European energy efficiency and sustainability goals.
• Versatility: a single system covers three needs: heating in winter, cooling in summer, and hot water all year round. It also integrates easily with systems like underfloor heating, low-temperature radiators, or fan coils.
• Increased property value: installing an air source heat pump improves the home's energy certification, increasing its market value. It is an investment that not only brings comfort and savings but also makes the flat more attractive to future buyers.

Requirements for installing an air source heat pump in a flat

Interior space (hydrokit + Hot Water Cylinder)

You will need a space similar to that of a boiler or a large fridge, usually in the kitchen, utility room, or a technical cupboard. If the system includes a hot water tank, the space must accommodate it.

Exterior space for the unit (terrace, patio, roof)

The heat pump must be placed in a ventilated and accessible location: a terrace, balcony, open drying area, or communal roof (with prior permission). It occupies approximately 1m³, similar to an air conditioning unit.

Accessibility for maintenance

Access must be guaranteed (without obstacles) for periodic inspections and repairs, for both the outdoor and indoor units.

Community permits (LOE + statutes)

If the installation affects the facade, roof, or common areas, authorisation from the Community of Owners is required, and in some cases, a minor works license. Check the Technical Building Code (CTE) and the Regulation of Thermal Installations in Buildings (RITE) to ensure compliance.

Recommended heat emitters

Air source heat pumps work best with underfloor heating or low-temperature radiators. They can also be combined with fan coils. If you have conventional radiators, they may need to be adapted.

Installing an air source heat pump in a flat (step by step)

1. Energy survey and technical visit

To start the process, a professional analyses the insulation, thermal demand, and available space to correctly size the equipment.

2. Choosing the system

There are two main types:

• Monobloc: the entire circuit is in the outdoor unit; ideal for limited spaces.
• Split (Bi-bloc): includes an indoor unit (hydrokit); more efficient for hot water and heating.

3. Location of the outdoor unit

The unit is installed on a terrace, balcony, or roof, on an anti-vibration base with good ventilation.

4. Installation of the indoor hydrokit

It is placed in the designated space (utility room, kitchen, or cupboard) and connected to the home's water circuit.

5. Connection to the existing heating system

The emitters (radiators, underfloor heating, or fan coils) are integrated, and the flow temperature is adjusted.

6. Pressure testing, gas charging, and commissioning

The installer checks for leaks, charges the refrigerant, and tests operation.

7. Configuration for winter and summer

Heating, cooling, and hot water modes are programmed, and the smart thermostat is set up.

Indicative installation costs

The price of installing an air source heat pump in a flat depends on several factors: surface area, type of emitters (radiators, underfloor heating), and the complexity of the work. To give you an idea:

• 70m² flat: estimated between €8,500 and €12,000, including the heat pump, hot water tank, and labour.
• 100m² flat: could range between €11,500 and €16,000, especially if radiators need adapting or fan coils added.
• Premium installation with underfloor heating: can reach €20,000, as it involves building work and longer installation time.
• Although the initial investment is significant, energy savings and potential subsidies (such as the Energy Rehabilitation Plan) help recover the cost in a few years.

What if I can't install an outdoor unit?

The outdoor unit is key to an aerothermal system, but lack of space or community restrictions means it isn't always possible in a flat. If this is your case, there are alternatives so you don't have to sacrifice efficiency:

Centralised aerothermal energy in the community

Some buildings choose to install a shared system on the roof or in common areas, with individual distribution via meters. This is an ideal solution for buildings looking to improve energy efficiency collectively.

Hybrid systems (heat pump + boiler)

If you cannot install the standard outdoor unit, you can combine a heat pump with your current boiler. This hybrid system reduces gas consumption and uses aerothermal energy for hot water and part of the heating, without replacing the entire installation.

Efficient electric alternatives

Another option is air-to-air heat pumps (which function as reversible air conditioning) or smart electric water heaters. They don't offer all the full benefits of a complete aerothermal system, but they are practical solutions to improve efficiency without major building works.

Important considerations before deciding

Before installing an air source heat pump in a flat, you should analyse key aspects to guarantee performance and avoid surprises:

• Thermal insulation: the better insulated the home, the higher the system's efficiency. Good insulation reduces heat loss and allows the heat pump to work at lower power, translating to savings.
• Contracted electrical power: the system needs electricity to run, so you may need to increase your contracted power capacity. This adjustment should be calculated during the preliminary survey to avoid tripping the main breaker or incurring extra costs.
• Regulations and permits: if the installation affects the facade, roof, or common areas, it is mandatory to consult the Community of Owners and the Town Hall. Complying with regulations (LOE, CTE, and RITE) guarantees safety and avoids fines.
• Subsidies and grants: programmes exist, such as the Energy Rehabilitation Plan, which can cover up to 40% of the installation cost. Taking advantage of these aids reduces the initial investment and speeds up the return on investment.

Analysing these points before deciding will help you plan better and get the most out of your air source heat pump installation.

In summary, installing aerothermal energy in flats is a smart investment for those seeking efficiency, comfort, and sustainability. With a good preliminary survey and professional installation, you can reduce your energy bill and help care for the planet.