Air to Air Heat Pump Efficiency: The Truth About EPC Ratings (2025 Guide)

Air to air heat pump efficiency figures are truly remarkable, achieving 300-400% efficiency compared to the 88-94% efficiency of traditional gas boilers. This means they produce three to four units of heat for every unit of electricity consumed, making them significantly more environmentally friendly than conventional heating systems.

Despite their impressive performance, there's confusion about whether heat pumps actually improve EPC ratings. When comparing a heat pump or gas boiler for annual costs, the difference might surprise you—the total estimated annual bill for heating and hot water using a heat pump is £806, just £9 cheaper than a traditional gas boiler. Nevertheless, heat pumps are gaining popularity, with a 41% increase in installations over the last 12 months compared to the previous year. In fact, of the 113,555 government-supported heat pump installations across the UK in the last five years, 99% were air source heat pumps.

In this guide, we'll explore everything you need to know about air to air heat pumps, their true efficiency, how they compare to traditional heating systems, and what they really mean for your property's EPC rating.

How air to air heat pumps work

Unlike traditional heating systems that generate heat by burning fuel, air to air heat pumps move existing heat from one place to another. This fundamental difference makes them an increasingly popular choice for UK homes seeking energy-efficient heating and cooling solutions.

What is an air to air heat pump?

At its core, an air to air heat pump is a system that extracts heat energy from outside air and transfers it directly into your home via a fan-based ventilation system. These systems are sometimes referred to as air conditioning units that can switch between heating and cooling functions depending on the season.

The setup typically consists of two main components: an outdoor unit installed on the exterior of your property and one or more indoor units mounted on walls or ceilings. Importantly, these heat pumps don't provide hot water—they're designed solely to warm or cool the air in your rooms.

How it transfers heat from outside to inside

The heat transfer process follows a straightforward refrigeration cycle involving four main components: evaporator, compressor, condenser, and expansion valve. Here's how it works:

1. The outdoor unit pulls in outside air through the evaporator, where refrigerant absorbs heat energy

2. This refrigerant (now a gas) moves to the compressor, which increases its temperature and pressure

3. The hot gas flows to the indoor unit, where fans blow room air across the condenser coils, warming it

4. Finally, the refrigerant expands through the expansion valve, cooling down before the cycle begins again

What's remarkable is that modern heat pumps can extract heat from air even in temperatures as low as -25°C, debunking the myth that they don't work in cold weather.

Heating and cooling capabilities

Perhaps the most valuable feature of air to air heat pumps is their dual functionality. During summer, the system simply reverses the process—absorbing heat from inside your home and releasing it outdoors. This provides year-round comfort through a single installation.

For multi-room properties, a 'multi' system allows connection of up to five indoor units to just one outdoor unit. Each room can have different temperatures, although you can't simultaneously heat one space while cooling another.

Through this heat-moving principle rather than heat-generating process, air-to-air heat pumps can deliver two to four times more heat energy than the electrical energy they consume, making them substantially more efficient than conventional heating methods.

Efficiency vs traditional systems

"Essentially, ANSI/ASHRAE 40-2025 establishes a standardised procedure to assess the capacity and energy efficiency of such units; this standard is used to determine the proper rating for these types of equipment based on their performance under controlled testing conditions." — ANSI/ASHRAE, International standards organisation

When evaluating heating systems, efficiency is where air to air heat pumps truly excel over traditional options. Understanding these differences helps explain why many UK homeowners are making the switch.

Heat pump efficiency explained (COP ratings)

The Coefficient of Performance (COP) is the standard measure of heat pump efficiency. Simply put, it's the ratio of heat output to electrical input. A COP of 3 means the heat pump produces three units of heat for every unit of electricity consumed. Most air source heat pumps achieve COPs between 2.5 and 4.5, making them remarkably efficient.

For seasonal performance, we use the Seasonal Coefficient of Performance (SCOP) or Seasonal Performance Factor (SPF). This measures efficiency across an entire heating season under varying conditions. The median SCOP observed in UK installations is 2.8 (280% efficiency), with many modern systems performing even better.

Gas boiler vs heat pump: energy use comparison

The efficiency difference between these systems is substantial. Modern gas boilers typically operate at 85-94% efficiency, meaning some energy is inevitably lost through flue pipes. Conversely, heat pumps achieve 300-400% efficiency, providing 3-4 times more heat for each kilowatt of electricity used.

This stark difference exists because heat pumps transfer heat rather than create it. A gas boiler burning 11,500kWh of gas might produce about 9,200kWh of usable heat output, whereas a heat pump using just 3,286kWh of electricity could deliver the same heat.

Impact of insulation on performance

Insulation plays a crucial role in heat pump efficiency. In well-insulated homes, heat pumps maintain consistent temperatures with less energy, operating at lower temperatures than traditional systems.

According to the Energy Saving Trust, approximately 25% of heat is lost through an uninsulated roof and around 33% through uninsulated walls. Proper insulation ensures that once a room is heated, that warmth remains trapped inside, allowing the heat pump to work less frequently and extend its lifespan.

Heat pump or gas boiler: which is cheaper to run?

Initially, many assumed gas boilers were cheaper to run because electricity costs more per unit than gas. However, the efficiency advantage of heat pumps offsets this difference. Recent research by the Regulatory Assistance Project reveals that heat pumps can be less expensive than gas boilers when properly installed.

The average cost difference? Running a heat pump on a standard tariff might cost approximately £10 more per month than a gas boiler. Yet with special heat pump tariffs now available, homeowners can save around £21 per month (£253 annually).

Ultimately, your actual savings depend on your home's insulation, the efficiency of your current boiler, and the electricity tariff you choose.

Do air to air heat pumps improve EPC ratings?

Energy Performance Certificates (EPCs) provide a standardised measure of property efficiency, but their relationship with heat pumps isn't straightforward. Many homeowners install heat pumps expecting an automatic boost to their EPC rating, only to be disappointed.

How EPC ratings are calculated

EPCs use the Standard Assessment Procedure (SAP) to assess energy performance on a scale from A (most efficient) to G (least efficient). The calculation primarily considers energy costs rather than carbon emissions or efficiency. This methodology converts energy consumption into a score between 1-100, which then translates to the familiar letter bands: A (92-100), B (81-91), C (69-80), and so forth.

Why heat pumps may not always boost EPC scores

Surprisingly, replacing a gas boiler with an air to air heat pump can sometimes lower your EPC rating. This counterintuitive result stems from electricity costs being substantially higher than gas - approximately £0.2450 vs £0.0624 per kWh. Consequently, despite heat pumps being 300-400% efficient compared to gas boilers' 90-95%, the higher energy price can unfavourably impact the cost-based EPC calculation.

Other upgrades that impact EPC more

For meaningful EPC improvements, focus first on:

• Effective insulation - addressing roof, wall and floor heat loss

• Updated windows and doors with proper sealing

• LED lighting throughout

• Smart controls for existing systems

When a heat pump does help your EPC

Heat pumps positively impact EPCs when replacing less efficient systems like electric storage heaters or LPG boilers. Additionally, properties with excellent insulation can achieve A or B ratings with heat pumps. As the UK electricity grid becomes greener, the EPC methodology is likely to evolve, eventually recognising heat pumps' environmental benefits more accurately.

Cost, grants and long-term value

"These performance requirements serve as the basis of eligibility for federal 25C tax credits up to $2000 enabled by the Inflation Reduction Act, as well as for leading utility financial incentives." — John Taylor, Executive Director of Consortium for Energy Efficiency (CEE)

Making the switch to an air to air heat pump represents a significant financial decision with important long-term implications for homeowners.

Installation costs vs gas boilers

The upfront investment for air source heat pumps typically ranges between £7,000 and £14,000, substantially higher than gas boilers that cost around £2,500-£3,000. This price difference creates an initial barrier for many considering the switch to more efficient heating technologies.

Running and maintenance costs

For a typical three-bedroom house, annual heat pump running costs average £734.69 for air source models, roughly comparable to gas boilers due to their superior efficiency offsetting higher electricity prices. Maintenance is straightforward but essential—annual servicing costs approximately £150-£300, slightly higher than gas boiler servicing at £72-£130.

Boiler Upgrade Scheme and other grants

Fortunately, the £7,500 Boiler Upgrade Scheme grant makes heat pumps far more affordable. This scheme is available to property owners in England and Wales replacing fossil fuel heating systems. Scotland offers a similar £7,500 grant through Home Energy Scotland.

Lifespan and return on investment

Heat pumps typically last 15-20 years compared to gas boilers' 10-15 years. Furthermore, they can increase property values by 5-10%. With grant support, the break-even point occurs after approximately 12 years, making them increasingly attractive as fossil fuel prices rise.

Conclusion

Air to air heat pumps undoubtedly represent remarkable technology with efficiency rates three to four times higher than traditional gas boilers. Their ability to extract heat from outdoor air even in sub-zero temperatures makes them an impressive engineering achievement. Nevertheless, the relationship between these systems and EPC ratings remains complex and often misunderstood.

Despite their superior efficiency, heat pumps might not automatically boost your property's EPC score due to the cost-based calculation methodology. This counterintuitive outcome stems primarily from the higher price of electricity compared to gas. Therefore, homeowners should consider complementary upgrades like proper insulation, which often yields more substantial EPC improvements.

Financial considerations certainly play a crucial role when deciding between heat pumps and conventional systems. The significant upfront cost difference between £7,000-£14,000 for heat pumps versus £2,500-£3,000 for gas boilers creates an initial barrier. Thankfully, the £7,500 Boiler Upgrade Scheme grant makes this transition far more affordable for many property owners.

Looking at the bigger picture, heat pumps offer compelling long-term value. Their extended lifespan of 15-20 years, potential to increase property values by 5-10%, and gradually improving running cost economics as electricity generation becomes greener all strengthen their appeal. Additionally, their dual heating and cooling functionality provides year-round comfort through a single installation.

The truth about air to air heat pumps and EPC ratings requires nuanced understanding. While they might not always deliver the immediate EPC boost many expect, their exceptional efficiency, decreasing operational costs, and environmental benefits make them a forward-thinking choice for UK homeowners. As energy regulations evolve to better reflect carbon impact rather than just energy costs, these systems will likely receive the EPC recognition they truly deserve.