Air source heat pump efficiency explained
With so many different heating options available, it can be difficult to decide which one is the best for your home. In this guide, we’ll take a deep dive into air source heat pump efficiency. We’ll look into all your burning questions - whether it’s “What is CoP?” or “Is a heat pump better than a boiler?”. Let’s explore whether this low-carbon heating alternative is the right choice for you.
How efficient are air source heat pumps?
An air source heat pump can be over 300% more efficient than a standard gas boiler(1). This means that for every unit of electricity used, a heat pump can generate over three units of heat to warm your home. In contrast, an A-rated gas boiler is 90% efficient, which means 10% of the energy it uses is wasted. Whilst upfront air source heat pump costs may be high to begin with, you could save money on your energy bills in the long run, depending on the type of heating system you're replacing. For example, you could save up to £1,200 per year by switching from old electric storage heaters to a heat pump(2).
Factors affecting efficiency
- Heat pump design - the way a heat pump is designed has a big impact on performance. Certain models are made to deliver higher efficiency, helping you save energy whilst keeping your home warm.
- Home insulation - did you know 25% of heat can be lost through your roof if your home isn’t properly insulated?(3) Adequate insulation means less heat leaves your home, therefore your air source heat pump doesn’t have to work as hard to keep it warm.
- Outdoor temperature - just like a gas boiler, your heat pump will work a bit harder in colder weather - but don’t worry, your air source heat pump will keep you warm in the coldest of UK winters.
- Regular maintenance - it’s important to look after your heat pump with regular maintenance. This means having it serviced once a year and keeping the area around it clear of leaves, overgrown plants, or snow in winter.
- Heat pump size - Heat pumps come in different sizes, and making sure yours is the right fit for your home is key to keeping it efficient. Our installers will ensure you get a system that’s designed specifically for your home.
How is the efficiency of an air source heat pump measured?
CoP, SCoP and SPF are common terms used to measure heat pump efficiency. Let's take a look at what they all mean.
What is CoP?
CoP stands for Coefficient of Performance. It’s a measure for the efficiency of a heat pump at a given moment in time, and it tells you how much heat is created for each unit of electricity used. The CoP tends to be between 2 and 5 for air source heat pumps, which means that for each unit of energy used by a heat pump, 2 - 5 units of heat are made.
What is SCoP/SPF?
SCoP stands for Seasonal Coefficient of Performance. This gives a broader view of heat pump efficiency over an entire season as opposed to a given moment in time. It’s also known as SPF - Seasonal Performance Factor. This measure considers changes in outside temperatures throughout the year, which can give you a better idea of how efficient a heat pump will be on average compared to the CoP. The SCoP typically ranges between 3 and 4 for modern air source heat pumps, with a higher value meaning better efficiency.
Does temperature affect heat pump efficiency?
Outdoor temperatures can affect the efficiency of a heat pump. Since air source heat pumps take heat from the air, they'll work harder when it's colder outside. The SCoP can help determine heat pump efficiency while accounting for changes in outside temperatures. It's calculated based on the system design of your home, considering average temperatures in your location and the size of your radiators.
How efficient are heat pumps in the winter?
Air source heat pumps are designed to work efficiently all year round, even in the coldest UK winters. Like boilers, they work harder in colder weather, but even then, they remain roughly three times more efficient than a standard gas boiler(4).
Efficiency of heat pumps vs boilers and other heating systems
For every unit of electricity used, you can get three to four times as much heat created by an air source heat pump. In comparison, an A-rated boiler converts only 90% of its fuel into usable heat, demonstrating that heat pumps are a lot more efficient than even the best-rated gas boilers!
| Air source heat pump | A-rated gas boiler | G-rated gas boiler | Electric boiler | Biomass boiler | |
| Efficiency | 300 - 400 % | 90% | <70% | Up to 99% | 80 - 91% |
How to improve heat pump efficiency
Although heat pumps are very efficient, there are many things you can do to ensure your heat pump continues to run efficiently:
- Setting the correct heating curve - this is set during your air source heat pump installation; it determines how much the heat pump should work to heat your home based on the outside temperature. If this is set incorrectly, it could increase running costs.
- Keep your heat pump on for extended periods - it’s best to keep your heat pump on all the time, but lower the temperature when you’re out or asleep instead of turning it off. This is because they are more efficient when they run for longer periods at lower temperatures.
- Heat pumps and radiators - heat pumps work best with radiators that have a larger surface area. We will advise you if you need to upgrade your radiators during your consultation with us.
- Regular maintenance - it's important to keep the area around your heat pump clear of any debris, like overgrown plants or snow build-up in the wintertime. This allows for unrestricted airflow, maintaining a high CoP.
- Regular servicing - your heat pump should be serviced annually to make sure it's running efficiently.
How much could you save with an efficient heat pump system?
The amount you could save on your energy bills depends on the running costs of your heat pump system and the type of heating system you’re replacing. Running costs can depend on a few things:
- The size of your radiators
- How the heat pump is controlled
- Your electricity tariff - with EDF, you can sign up for our exclusive heat pump tariff featuring twice-daily discounts.
See how much you could save in the table below. We compare potential annual savings from installing an air source heat pump in a three-bedroom semi-detached home with necessary radiator upgrades(2):
| Existing System | Annual Savings |
| Old electric storage heaters | £1,200 |
| New electric storage heaters | £700 |
| Old (G-rated) LPG boilers | £700 |
| Coal | £700 |
| New (A-rated) LPG boilers | £270 |
| Old (G-rated) gas boilers | £260 |
| Old (G-rated) oil boilers | £65 |
| New (A-rated) gas boiler | £-40 |
| New (A-rated) oil boiler | £-220 |
With annual savings of up to £1,200 and the possibility of lowering your carbon footprint by 12%(5), installing an air source heat pump can help you save cash and carbon... want to find out more about the installation process? Check out our air source heat pump installation guide for a full overview.
As a Which? trusted trader, you can rest assured that EDF heat pumps will deliver on both performance and value. Still unsure? Switching to a heat pump is easy with our Heat Pump Promise - if it doesn't perform as promised, we'll give you your money back (T&Cs apply). You could also be eligible for an air source heat pump grant of up to £7,500 to assist with installation costs. Ready to make the switch?
Do air source heat pumps work efficiently with existing radiators?
Heat pumps can work with existing radiators, but they'll be most efficient with larger radiators, as they have a greater surface area to emit heat to warm your home.
How quickly does an air source heat pump heat a room?
This depends on various factors like home insulation, radiator size and the temperature you're trying to reach. It can take anywhere from 30 minutes to several hours to warm a room. It's best to keep your heat pump running constantly and lower the temperature when you aren't at home for the most efficient usage.
Are there any seasonal tips to improve heat pump efficiency?
Your heating curve should be adjusted according to the outside temperature to ensure the heat pump flow temperature is lowered in warmer outdoor weather conditions. This ensures your running costs aren't higher than they should be, as your heat pump will never be working harder than it needs to. Your installer will set this when you first get your heat pump. This is also known as outdoor weather compensation.
It's also good to be aware of any debris that could collect in your heat pump and disrupt airflow in different seasons, such as leaves in autumn, pollen buildup in summer, or snow in winter. Make sure you're clearing your heat pump seasonally to allow for uninterrupted airflow.
Do heat pumps require a lot of maintenance?
We recommend annual servicing by an MSC certified engineer to make sure the system is working efficiently and maintain your warranty. Other than that, all you have to do is keep the area around your heat pump clear and clean or change your filters as needed.