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Last updated: 11th April, 2024


Air Source Heating

Air Source Heating

Key takeaways

  • Air source heat pumps utilise outdoor air to efficiently heat homes and water.
  • They offer energy savings and low-carbon benefits, balancing initial costs with long-term financial and environmental gains.
  • Proper evaluation of installation requirements and performance expectations is essential for homeowner satisfaction.

Air source heating harnesses environmental warmth to heat homes efficiently, utilizing a device known as an air source heat pump.

Air source heat pumps represent a significant advancement in home heating technology, harnessing the energy from the outside air to heat domestic spaces and water.

These systems operate by extracting the natural warmth from the external air, even at low temperatures, and using a heat exchanger and refrigeration process to amplify and transfer this heat indoors.

As a low-carbon method of heating, air source heat pumps are becoming an increasingly attractive option for homeowners looking to reduce their carbon footprint and dependence on traditional fossil fuels.

The installation and operational costs of these systems are counterbalanced by their long-term energy savings and the potential for financial incentives.

By adopting air source heat pumps, homeowners can benefit from lower heating bills and increased energy efficiency compared to conventional boilers.

While the upfront costs can be noteworthy, the long-term savings, coupled with a typically lower maintenance requirement, make air source heat pumps a compelling option for modern, eco-conscious living.

Although generally considered less intrusive to install than their ground source counterparts, air source heat pumps require careful consideration of the property's insulation and the overall compatibility of the existing heating system. Users should also weigh the performance characteristics, such as their operation at lower temperatures compared to traditional boilers, and the impact this may have on comfort levels within the home.

Basics of Air Source Heating

Air source heating harnesses environmental warmth to heat homes efficiently, utilizing a device known as an air source heat pump. This section explores the heat pump mechanism, distinguishes between common system types, and identifies the key components.

Understanding Heat Pumps

An air source heat pump is a clever device that extracts warmth from the air outside even when temperatures are low. They operate on a basis that is akin to how a refrigerator works, but in reverse. Through the process, they manage to provide heat sufficient for both space heating and domestic hot water.

Types of Air Source Heat Pumps

Air source heat pumps come predominantly in two configurations:

  1. Monobloc Systems: These systems house all components in a single external unit. Pipes extend from this unit to convey water to your dwelling's central heating and hot water cylinder.

  2. Split Systems: Split systems distribute components between an indoor and an outdoor unit. Connectivity between the two allows heat transfer into your home.

Components of an Air Source Heat Pump

The primary parts of an air source heat pump include:

  • Compressor: Increases the temperature of the refrigerant by compressing it, thus increasing its heat.

  • Condenser: Here, the heated refrigerant transfers its warmth to the heating and hot water systems of the home.

  • Heat Exchanger: This apparatus facilitates the absorption of heat from the outside air into the refrigerant within the heat pump system.

By utilising these components, air source heat pumps provide an energy-efficient heating solution.

Key Features of Air Source Heating

Air source heating systems stand out for their remarkable energy efficiency and environmental benefits. They offer a promising avenue for reducing household carbon footprints while also being supported by government-backed financial incentives.

Energy Efficiency

Air source heat pumps (ASHPs) are lauded for their ability to deliver three times more energy than they consume. This is due to their high coefficient of performance (COP), which measures the ratio of heat output to electricity input. For instance:

This means that when a boiler may require 1kWh of energy input for less than 1kWh of energy output, ASHPs will typically produce 3kWh of heat for every 1kWh of electricity used.

Reduced Carbon Footprint

By leveraging the ambient air, ASHPs reduce reliance on fossil fuels, aligning with a low-carbon pathway. Since the heat is sourced from renewable energy in the exterior environment, this contributes to a significant reduction in a household's carbon footprint. The green nature of this technology is vital in combating climate change.

Eligibility for Government Grants

United Kingdom residents can access the Boiler Upgrade Scheme to make the transition to ASHPs more cost-effective. Financial incentives include:

  • Grants up to £7,500

  • Support for installations in both new and existing homes

This scheme is part of the broader move towards renewable heat solutions encouraged by the government's commitment to renewable energy. Homeowners are incentivised to adopt green heating systems, fostering the growth of sustainable and environmentally friendly practices.

Installation and Costs

A decisive factor for homeowners considering air source heat pumps is the balance between the initial outlay and long-term benefits. Accurate cost estimation and awareness of financial support mechanisms are essential for savvy investment in renewable heat.

Assessment and Installation

Prior to installation, a thorough assessment of the property is crucial to determine suitability. An installer will evaluate insulation, existing central heating systems, and electricity supply to ensure efficient integration. The process typically includes the placement of an external unit and any necessary modifications to the existing heating system.

Cost Analysis

Air source heat pumps present a significant upfront investment but can offer long-term savings. Typical installation costs range from £6,000 to £19,000, heavily influenced by the size and type of system. Running costs vary, hinging on the insulation quality of the home and the efficiency of the pump, estimated between £685 and £1,550 annually.

  • Initial Costs: £6,000 - £19,000

  • Annual Running Costs: £685 - £1,550

  • Potential Savings: Replacing a gas boiler with a heat pump can yield up to £340 in savings a year.

Grants and Incentives

The UK government provides financial incentives to mitigate the setup expenses:

  • Boiler Upgrade Scheme: Offers vouchers to offset installation costs.

  • Renewable Heat Incentive: Pays participants for the renewable heat generated.

  • Home Energy Scotland: Provides loans and grants specifically for residents in Scotland.

These schemes significantly reduce the net cost and accelerate the return on investment for homeowners adopting air source heat pump technology.

Operation and Performance

Air source heat pumps (ASHPs) represent a significant shift in home heating technology, challenging traditional systems with their ability to convert electricity into multiple units of heat. This section delves into the nitty-gritty of ASHPs, focussing on their efficiency, impact on household energy expenditure, and essential maintenance considerations.

Efficiency Metrics

Air source heat pumps are evaluated primarily on their Coefficient of Performance (COP) and Seasonal Coefficient of Performance (SCOP). COP measures the heat output to electricity input ratio at a given time, whilst SCOP assesses this over a season, providing a more realistic efficiency metric under varying weather conditions. Typical COP values for ASHPs range between 2 and 4, implying that the system can produce 2 to 4 units of heat for every unit of electrical energy consumed.

Impact on Energy Bills

The adoption of ASHPs can materially affect household energy costs. The operational efficiency of these systems, particularly when compared to traditional gas boilers, leads to lower energy consumption. Given that ASHPs can attain an efficiency upwards of 200% to 400%, households often observe a significant reduction in energy bills. However, initial installation costs and electricity prices are factors to consider in the overall financial impact.

Maintenance and Aftercare

Maintaining an air source heat pump involves regular check-ups and cleaning of filters, fans, and coils to prevent performance degradation. Although aftercare may incur costs, the continued efficiency and longevity of the ASHP rely on this upkeep. Typically, manufacturers offer a warranty, and service contracts may be available to help spread these costs over time, ensuring the system performs optimally and achieves its expected lifespan.

Air Source Heat Pumps vs New Boilers

When considering heating options, consumers are often faced with the choice between air source heat pumps and new boilers. Both systems have distinctive features that may sway a decision based on preferences for efficiency, sustainability, and cost.

Air source heat pumps (ASHPs) harness electricity and atmospheric warmth to heat homes. They are admired for their sustainability and have gained traction as a part of the Warm Home Promise. Advantages include lower carbon emissions and the potential to be fuelled by renewable energy, aligning with the UK's commitment to reducing greenhouse gas emissions.

However, ASHPs often come with higher initial costs compared to boilers. Installation can range from £14,000 to £19,000. Noise can also be a factor; while generally quiet, they do make some noise during operation. On the upside, Octopus Energy and other suppliers sometimes offer incentives to mitigate costs and promote the transition to sustainable solutions.

In contrast, new boilers typically involve a lower upfront expense, somewhere between £500 and £3,000, plus installation fees. Boilers can rapidly heat a space and work with existing high-temperature systems like radiators, which can make them a preferable retrofit option.

Nevertheless, boilers can have higher running costs and are less environmentally friendly, often relying on the burning of fossil fuels — such as gas or oil — to generate heat. Their efficiency is lower than ASHPs, as they do not leverage the heat multiplier effect that ASHPs do.


Air Source Heat Pumps

New Boilers

Initial Cost




More sustainable

Less so

Running Cost

Typically lower


Heat Production

Slower, at lower temps

Quick, high temps


Some operational noise

Generally quiet

In summary, while a new boiler might be less burdensome on the wallet initially, air source heat pumps offer a greener, cost-efficient solution in the long run. Deciding factors will include a user's sustainability goals, budget, and heating needs.

Exploring New Boilers and Their Efficiency

The landscape of domestic heating is evolving with efficiency taking centre stage. Innovations in boiler technology offer significant energy savings and reduced carbon emissions.

Modern Boiler Types: Combi/System/Heat-Only

Combi Boilers - These boilers combine central heating with hot water in one device. Upon demand, they deliver hot water directly from the mains without the need for a storage tank.

  • Pros: Space-saving, efficient, and provides hot water on demand.

  • Cons: Limited hot water flow which may not suit homes with multiple bathrooms.

System Boilers - These require a cylinder for storing hot water, but all other major components are built into the boiler.

  • Pros: Can provide hot water to multiple taps at once.

  • Cons: Hot water is not instant; cylinder space is needed.

Heat-Only Boilers - Also known as conventional boilers, they require a cold water tank and a hot water cylinder.

  • Pros: Suitable for homes with traditional heating systems.

  • Cons: More space required, not as efficient as combi or system boilers.

Why Are Combi Boiler So Popular in the UK?

Combi boilers have gained popularity across the UK for their efficiency and ease of installation. Three key factors contribute to their favoured status:

  1. Space-Saving Design: Ideal for smaller homes and flats with limited space.

  2. Energy Efficiency: They only heat water as it's used, reducing wastage and energy bills.

  3. Convenience: Instant access to hot water without waiting times.

In terms of professional development, engineers in the UK are trained rigorously to install and maintain these modern boilers. They are educated about the subtleties of each system, ensuring that the right type of boiler is fitted for each home, factoring in its size, usage patterns, and existing infrastructure. Continuous training keeps them abreast of the latest advancements in boiler technology, ensuring they're equipped to provide the most energy-efficient solutions.

Comparative Analysis

Evaluating air source heat pumps involves scrutinising their energy efficiency, cost implications, and environmental impact against alternative heating systems.

Energy Efficiency Comparison

  • Air source heat pumps (ASHPs), particularly air-to-water systems, can operate with a Coefficient of Performance (COP) of roughly 3.2 at 7°C ambient temperature. They harness low-grade heat from the air and upgrade it to provide heating.

  • In comparison, ground source heat pumps (GSHPs) typically achieve a higher COP, often around 4.0, given the more stable ground temperatures.

  • The efficiency of ASHPs can plummet in colder climates, hence they must work harder, at times reducing the COP to below 2.

Cost Implications

  • The initial expenditure for ASHPs is usually less than for GSHPs. Installation doesn't necessitate extensive groundworks, thus reducing the upfront costs.

  • Over time, households with ASHPs might see a raise in operational expenses during colder months, as reduced efficiency necessitates increased electricity use.

  • Despite these higher running costs, the investment may still be viable. The average return on investment (ROI) period for an ASHP is estimated at 7-10 years, depending on regional electricity prices and the pre-existing heating system replaced.

Environmental Impact

  • ASHPs lessen dependency on fossil fuels by utilising electricity, which can be generated from renewable sources.

  • The environmental advantage of ASHPs intensifies as the grid becomes greener, with increased renewable energy sources leading to further reductions in carbon emissions.

  • Yet, their efficacy and, by extension, their environmental benefits diminish in extremely cold climates. Therefore, supplementing ASHPs with other low-carbon or renewable heat sources may be necessary for those regions.

In depth Pros and Cons

This section delves into the detailed advantages and disadvantages of air source heating compared to modern gas boilers; examining their impact on hot water production, integration with systems like underfloor heating, and the financial and regulatory considerations involved.

Pros of Air Source Heating

  • Reduced Carbon Footprint: Air source heat pumps (ASHPs) have the capacity to lower household carbon emissions, with some units reaching an efficiency rating of 300%. This efficiency translates to more heat output per unit of electricity consumed compared to conventional heating methods.

  • Renewable Energy Utilisation: ASHPs harness heat from the air, an abundant and renewable energy source, diminishing reliance on fossil fuels.

Integration with Heating Systems:

  • Underfloor Heating: ASHPs pair well with underfloor heating, offering an even distribution of warmth at a lower operating temperature.

  • Radiators: They can also connect to a wet central heating system with larger radiators designed to operate at lower temperatures typical of heat pumps.

Costs and Grants:

  • While initial installation costs can be high (upward of £13,500 for a 10kW pump), potential government incentives and reduced operational costs can offset the price over time.

  • Permitted developments typically do not require planning permission for installing ASHPs, simplifying the installation process.

Cons of Air Source Heating

  • Higher Initial Outlay: Installation costs for ASHPs are considerable. An average 10kW system might cost £6,000 plus installation, which could total £13,500. Existing homes may incur higher installation expenses due to retrofitting challenges.

Inefficiency in Extreme Cold:

  • During frigid conditions, ASHP efficiency may decline, reducing effectiveness and increasing running expenses.

Space and Noise:

  • ASHP units require external space. Noise is a factor, which, although comparable to those made by modern gas boilers, needs consideration regarding placement and any impact on neighbours.

Pros of New Gas Boilers

  • Compatibility and Familiarity: Gas boilers are commonly used and compatible with existing heating systems, such as radiators and wet central heating.

  • Lower Initial Costs: The upfront costs for purchasing and installing a new gas boiler are typically lower than those for ASHPs, making it a more accessible option initially.


  • They offer reliable and robust performance, including high-temperature heating, suitable for traditional smaller radiators.

Cons of New Gas Boilers

  • Non-Renewable Fuel Source: Gas boilers burn fossil fuels, contributing to carbon emissions and not aligning with future carbon-neutral targets. Alternatives like oil or LPG boilers share similar issues and costs can be volatile.

  • Energy Efficiency: New gas boilers, while more efficient than older models, do not match the high efficiency of ASHPs, especially when considered over the longer term.

Regulatory Changes:

  • With increasing regulatory changes, the future installation of gas, oil, or coal boilers may be restricted, potentially impacting longer-term viability.

Cost of Fuel:

  • Although installation costs are less, the long-term cost of fuel, subject to market fluctuations, can make gas boilers more expensive to run over time compared to ASHPs that use cheaper, renewable electricity.

Ground Source Heat Pump Comparative Analysis

This comparative analysis examines the distinctions and relative advantages between air source and ground source heat pumps in the context of central heating systems.

Air Source vs Ground Source

Air source heat pumps (ASHPs) operate by extracting heat from the ambient air, which fluctuates with weather conditions, potentially affecting the system's efficiency. Conversely, ground source heat pumps (GSHPs) harness heat from the ground; this source remains at a more constant temperature, thus providing a consistent performance year-round. ASHPs generally need less installation space and can be fitted externally to buildings, presenting a more flexible solution in urban areas where outdoor space is at a premium.

While ASHPs transfer heat from the air to a building's interior directly in an air-to-air system, or to water in an air-to-water system, GSHPs require the installation of pipes in the ground, either via deep boreholes or horizontal trenches. These pipes form a loop containing a mixture of water and antifreeze, which absorbs ground heat and is compressed to increase its temperature before being passed into the central heating system.

Cost-Benefit Comparisons


Air Source Heat Pumps

Ground Source Heat Pumps

Initial Installation

Approximately £14,000

Around £28,000

Running Costs

Lower than conventional boilers

Typically lower than ASHPs when well-designed

Efficiency Improvements

Notable compared to gas boilers

Superior, leveraging stable ground temperatures

The purchase and installation costs of GSHPs are notably higher than those of ASHPs primarily due to the extensive groundwork involved. Although the initial financial layout can be significant, GSHPs often attract higher renewable heat incentives due to their efficiency and reduced environmental impact. When considering the running costs, the GSHP's proficiency can yield substantial savings on electricity tariffs, surpassing the air source variant, especially in areas with extreme climates. Both heat pump systems represent a considerable reduction in running costs when compared to conventional boilers fuelled by fossil fuels.

In terms of heat loss, ASHPs can be subject to reduced effectiveness during cold spells, leading to an elevated demand on electricity to maintain performance. GSHPs, with their use of constant ground temperatures, experience fewer issues related to external temperature variations, ensuring a more stable operation.

When evaluating the two, one must weigh the higher upfront cost of GSHPs against the lower running costs and potential for greater long-term savings. Investors are encouraged to consider both systems within the actual context of their energy needs, space availability, and up-front budget constraints.

Financial Considerations

When exploring the viability of air source heat pumps for home heating, financial implications sit at the forefront of the decision-making process. The upfront costs, the potential for long-term savings and available financial support schemes each play a crucial role.

Long-Term Savings

An air source heat pump (ASHP) brings significant long-term savings due to greater energy efficiency compared to conventional heating systems. An ASHP can convert 1 kWh of electricity into three times as much heat, reducing annual heating costs. For instance, heating a home with an ASHP could cost about £980 per year, versus £1,044 with an LPG boiler.

Initial Outlay vs Ongoing Expenses

The initial outlay for an ASHP fluctuates based on the system type and property size. Installation can range from £2,000 to £15,000, whereas a mid-sized home may incur costs closer to £3,000 to £4,000 for the unit itself. These expenses are offset by the ASHP's efficiency, leading to reduced electricity tariffs in the long term, thus balancing the initial investment against the ongoing expenses.

Financial Support Schemes

The UK government offers financial support through incentives like the Boiler Upgrade Scheme, which encourages homeowners to switch to more sustainable heating options. Those eligible could receive a grant of up to £7,500 towards the installation of an ASHP, underpinning the transition to renewable heat sources. Additional incentives previously available, such as the Renewable Heat Incentive, have been pivotal in easing the financial burden of adopting green technologies.

Integration with Other Systems

In the transition towards low-carbon heating, the integration of air source heat pumps with other systems presents an opportunity to enhance energy efficiency and manage energy costs in residential settings.

Combining with Solar Panels

Air source heat pumps (ASHPs) can be effectively combined with solar panels to create a highly efficient, renewable energy solution. Solar panels convert sunlight into electricity during the day, which can then be used to power ASHPs. This synergy not only reduces reliance on the grid but also trims down electricity bills and carbon emissions. The integration achieves an energy-independent setup that provides a buffer against energy price fluctuations.

  • Advantages:

    • Reduced energy bills

    • Increased energy independence

    • Lower CO2 emissions

Hybrid Heating Solutions

Integrating ASHPs with existing central heating systems can necessitate additional components to ensure compatibility and optimise performance. For instance, larger radiators or underfloor heating may be required to accommodate the lower operating temperatures of ASHPs. Additionally, the use of a buffer tank may prevent short cycling and ensure a consistent level of warmth is maintained.

  • Components for Integration:

    • Underfloor Heating: for distributing heat efficiently.

    • Buffer Tanks: to ensure consistent heating and minimise wear.

Smart Home Integration

The advent of smart technology enables sophisticated integration of ASHPs into smart home systems. Homeowners can now leverage smart thermostats and devices to dynamically adjust heating schedules and temperatures, optimising the performance of their heating systems for comfort and efficiency. Smart integration not only enhances user convenience but also contributes to energy savings and lower carbon footprint.

  • Smart Features:

    • Remote control of heating

    • Dynamic adjustment to weather patterns

    • Usage tracking for informed decision-making

The UK's approach to integrating air source heating into the energy mix is shaped by an evolving legal and policy framework. This framework aims to balance the promotion of renewable energy uptake with sound regulatory oversight.

Regulations and Standards

The UK Government mandates that the installation of air source heat pumps (ASHPs) comply with certain regulations and standards to ensure safety, efficiency, and minimal environmental impact. Planning permission may be required for ASHPs, particularly in conservation areas or on listed buildings. Noise emissions are a key concern, as outlined by the Department for Energy Security and Net Zero, which commissioned a review of noise emissions in 2023. ASHP installations must adhere to:

  • Noise Emissions: Conformity with the UK's permitted development regulations, which include specific sound level limitations.

  • Building Regulations: Compliance with parts L (Conservation of fuel and power) and F (Ventilation) for energy efficiency and system ventilation requirements.

Incentive Programmes

The UK Government encourages the uptake of renewable heating technologies through various incentive programmes. Government grants, such as the Renewable Heat Incentive (RHI), support the shift towards renewable energy by providing financial incentives for those who install renewable heating technologies. Key points include:

  • Renewable Heat Incentive: A scheme designed to financially reward users of renewable heat, aiming to offset the cost disparity between conventional and renewable heating systems.

  • Government Grants: Availability of grants to help cover the upfront costs of installing ASHP systems, subject to eligibility criteria.

This framework underpins the UK's commitment to reducing emissions and transitioning to a more sustainable heating future.

New Boiler Costs

Boilers can be a daunting purchase for many people as they’re an appliance with a lot of responsibility, providing heat for you and your family is something you want to get right. Boilers aren’t exactly a quickly disposable item either, potentially lasting you a decade.

Effectively, new boiler cost can be split into two segments: the first is the actual boiler itself (unit price), and the second is the cost of the boiler being installed (set up) in your property by an expert engineer. 

Here at iHeat, we want to remove all of this undue stress and make the decision making process of upgrading to a new central heating system, as easy as possible.

Boiler costs can vary depending on a number of factors including their brand, model, fuel, output, warranty, labour and installation type. Typically a new boiler will cost between £1,845 and £3,500, below is a list of average boiler installations offered by iHeat (guide only).

Installation Type

Price (inc VAT)

Combi to combi swap


Get a quote

System to combi conversion


Get a quote

New boiler install


Get a quote

Back boiler to a combi


Get a quote

System to system


Get a quote

Frequently Asked Questions

What are the disadvantages of air source heating?

Air source heat pumps may have higher upfront costs than conventional boilers and can be less effective in extremely cold temperatures. They also require space outside the property for installation.

Is air source heating expensive to run?

Running costs of air source heat pumps can be lower than those of oil or LPG boilers, though electricity prices affect overall expenses. The systems are generally more efficient, translating to potential savings.

Does air source heating use a lot of electricity?

Although air source heat pumps utilise electricity, they are efficient systems typically producing more heat energy than the electrical energy they consume, leading to a lower overall electricity usage compared to traditional electric heaters.

Is air source heating any good?

Air source heating is a good option for many, providing efficient heating and a reduction in carbon footprint. It is particularly effective when paired with underfloor heating or specially designed radiators.

Why are heat pumps not popular in the UK?

Heat pumps have historically been less popular in the UK due to the prevalence of gas boilers, insufficient consumer awareness, and the cost implications associated with transitioning to a heat pump system.

What homes are not suitable for heat pumps?

Homes without sufficient outdoor space for the heat pump unit, those with poor insulation, or properties that rely on high-temperature heating systems may not be ideal candidates for heat pump installation.

Why heat pumps may not be the future?

While heat pumps are a promising technology, their future dominance is not guaranteed. Potential hurdles include high installation costs, the need for better insulation standards in homes, and the current electric grid's ability to handle increased demand.

Stephen Day profile photo
Article by
Stephen Day | Co-founder
Gas Safe registered and FGAS certified engineer with over 20 years experience in the heating and cooling industry.