Can an air source heat pump heat a whole house?

can an air source heat pump heat a whole house
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    Energy efficiency is a hot topic for all homeowners as we strive to keep our homes consistently warm and minimise our energy bills. Heat pumps are gaining more popularity as a highly efficient, low-cost solution that also helps to reduce carbon emissions.

    However, many still have doubts about the effectiveness of air source heat pumps, particularly in the UK, where air temperatures are variable. As installers of heat pumps at Cinergi, we understand these apprehensions all too well. So, can a heat pump heat a whole house effectively?

    An air source heat pump can heat an entire house via a new or existing central heating system. How efficient a heat pump system is depends on factors such as how well-insulated the home is. To achieve the best results, it is important to consider a hybrid solution with a boiler.

    In this article, we will delve into how modern heat pump systems can be used with an existing heating system to warm an entire home, as well as reliably supply hot water. We’ll examine what factors determine how efficient heat pumps are and when a hybrid system is the best choice.

    For friendly, impartial advice on heat pumps, please get in touch with Cinergi.

    How does an air source heat pump generate heat for a house?

    Air source heat pumps work by converting heat energy from the outside air and transferring it inside to provide both heating and hot water for homes.

    Heat extraction

    An air source heat pump starts the heating process by extracting heat from the surrounding air via an outdoor unit. Despite outdoor temperatures, there is always some level of thermal energy present in the atmosphere, even in cold climates.


    A refrigerant gas is pressurised, increasing its temperature. This process intensifies the thermal energy within the gas, enabling it to transfer heat more efficiently. The compressed gas then moves to the condenser, where it releases heat into the indoor space.

    Heat transfer

    The pump transfers heat to indoor space using a network of pipes connected to an indoor unit and then to the new or existing heating system (e.g., radiators or underfloor heating).

    By efficiently cycling through these stages, an air source heat pump effectively harnesses ambient heat from the environment and converts it into a usable form for indoor heating.

    Not only is it reliable, it is energy efficient and can significantly reduce your carbon footprint when compared with traditional heating systems.

    What factors influence how well air heat pumps work?

    Several factors influence the efficiency and effectiveness of air source heat pumps:


    While air source heat pumps can extract warm air even in cold weather, they are more efficient in warmer temperatures.


    A poorly insulated home results in heat loss, leading to increased energy consumption and reduced overall efficiency. Good insulation helps minimise heat loss and contributes to increased heat pump efficiency.

    System size

    A professional survey and accurate heat loss calculations are crucial for determining the appropriate size of the heat pump required to ensure optimal performance.

    Installation quality

    Proper installation by qualified and MSC accredited heating professionals like Cinergi is crucial for maximising heat pump performance and longevity.


    Regular maintenance ensures the heat pump’s optimal functioning over time. Fortunately, maintenance costs for heat pumps are comparably low compared to a traditional boiler.

    Why a hybrid heating system should be considered

    Any combination of the factors mentioned above can make it unfeasible or financially unviable to use a heat pump to warm an entire house. In these instances, you may opt for a hybrid system.

    A hybrid system is a heat pump coupled with an additional fuel source, such as a gas or oil boiler. In this scenario, the heat pump delivers a percentage of the property’s heat demand, but when the external temperature drops too low, the boiler takes over.

    This may sound counterintuitive; however, the decreased reliance on fossil fuels means that homes can still significantly reduce their carbon emissions and enjoy energy savings.

    Hybrid system example

    The most important factor is determining the property’s heat requirement (or peak heat loss).

    Here’s an example of a property with a 20kW peak heat loss:

    On a standard 100amp domestic electricity supply (single phase), the largest single air source heat pump can provide in the region of 16.5kW and is therefore not capable of heating the property alone. Installing a 12kW heat pump will likely be more cost-effective.

    The below figures are based on a Vaillant aroTHERM Plus 12kW heat pump, at a design flow temperature of 50c.

    • Property total peak heat loss @ -2c = 20kW
    • Air source heat pump (ASHP) output at -2c = 12.6kW
    • The ASHP can provide 63% of the heat load. If coupled with a gas boiler with an output of around 30kW c adequately cover the property’s heat requirement
    • The ASHP can provide all the property’s heat requirements when the external temp of 5c or above (this is called the bivalent point). Below this temp, the heat pump will switch off, and the gas boiler will take over.
    • Despite the heat pump providing only 63% total coverage at -2c, it is not often that cold in the south of England. Therefore, the ASHP will provide approximately 89% of the property’s annual heat requirement.

    It is worth noting that in order to qualify for the Boiler Upgrade Scheme (BUS) voucher, a heat pump must be capable of heating the whole property and your old gas or oil boiler must be removed.


    Can I cool my house using an air source heat pump?

    In warmer weather, an air source heat pump has the capacity to cool the air in your home, but its effectiveness depends on how the cold water energy is transferred into the property.

    Conventional radiators are unsuitable for cooling as they generate condensation. Underfloor heating (UFH) can provide cooling, however, it typically only achieves a modest 2°C drop in room temperature.

    Using a heat pump to cool a house also requires its pipework to be insulated along its entire length. This is usually unfeasible in an existing property, but it is possible on new build projects.

    Do I need an air heat pump or a ground heat pump?

    Whether you need an air or ground heat pump depends on factors like space availability and budget. Air-source heat pumps are typically more affordable, easier to install and, therefore, suitable for most homes.

    Ground source heat pumps offer higher efficiency but require more space and a larger initial investment, making them better suited for larger properties with adequate land. See our ground source heat pump services.

    Consulting with a qualified HVAC professional like Cinergi can help determine the best option based on your specific needs, budget, and property characteristics.

    Talk to Cinergi for all your air source heat pump requirements

    If you are considering a new heat pump system or hybrid solution, Cinergi is here to help. With over 40 years of experience in domestic heating, we can provide independent advice on finding the right home heating solution for your property.

    Contact us today for a free discovery call, visit our FAQs page for more helpful advice, or read our ASHP reviews here.

    Picture of Dan Loveridge
    Dan Loveridge

    Dan is the managing director at Cinergi, a renewable energy company based in southern England specialising in air source heat pumps and EV charging solutions.

    Contact us to ask for advice