Why Is My Air Source Heat Pump Expensive to Run

Air source heat pumps are widely promoted as an efficient and environmentally friendly way to heat a home. They use electricity to transfer heat from the outside air into your property, making them a renewable alternative to traditional gas or oil boilers. However, many homeowners report that running costs can seem higher than expected, especially during colder months. If you are asking why your air source heat pump is expensive to run, the answer is often a combination of system design, property insulation, user habits, and tariff choices. Understanding these factors is the first step to improving efficiency and managing energy bills.

How air source heat pumps work

An air source heat pump extracts heat from the outside air and transfers it into your home through a refrigerant cycle. Even when outdoor temperatures are low, there is still usable heat energy that can be captured. The system then delivers this heat via radiators, underfloor heating, or hot water systems. Unlike a gas boiler that produces heat instantly at high temperatures, heat pumps work more efficiently at lower, steady temperatures. This means they are most effective when running continuously rather than being switched on and off.

Property insulation and heat loss

One of the biggest reasons why running costs feel high is poor insulation. Heat pumps are designed to provide low temperature heat consistently, but if the property loses heat quickly through walls, windows, or the roof, the system has to work harder to maintain comfort. Older houses with minimal insulation or single glazing can see significantly higher electricity use compared to modern, well-insulated homes. Improving insulation levels, sealing draughts, and upgrading glazing can make a noticeable difference to efficiency. Without these measures, a heat pump may appear costly because it is compensating for avoidable heat loss.

System design and installation quality

The design and installation of an air source heat pump have a major impact on running costs. If the system is undersized for the property, it will struggle to provide adequate heating and consume more energy. Similarly, if the heat distribution system is not suitable, such as radiators that are too small for low flow temperatures, the pump will need to run at higher settings, reducing efficiency. A correctly sized and properly designed system should keep running costs competitive with gas or oil, but poor installation often leads to disappointment. Using a qualified installer with knowledge of heat pump design is vital.

Electricity tariffs and costs

Because heat pumps are powered by electricity, the cost of running them is directly tied to electricity tariffs. In the UK, electricity is typically more expensive per kilowatt-hour than gas. This can make heat pumps look costly even if they are efficient. Homeowners can reduce costs by exploring time-of-use tariffs, such as Economy 7 or smart tariffs, where electricity is cheaper during off-peak hours. Pairing a heat pump with solar panels and battery storage can also help offset electricity costs. Without considering tariffs, the system may seem expensive simply because of the unit price of electricity.

Seasonal performance and weather conditions

The efficiency of an air source heat pump is measured by its coefficient of performance (COP). In mild conditions, a pump may achieve a COP of three or more, meaning for every unit of electricity it consumes, it delivers three units of heat. However, in colder weather, the COP falls because the pump has to work harder to extract heat from the air. This means that during winter, electricity use increases and costs rise. While this is normal behaviour, it can feel expensive compared to the steady costs of a gas boiler. The key is to remember that performance varies across the seasons.

User habits and system settings

Another factor in high running costs is how the heat pump is used day to day. Heat pumps are not designed to provide fast bursts of heat like a gas boiler. If the system is switched on and off regularly or set to high temperatures, efficiency drops. The most cost-effective way to run a heat pump is to keep it on continuously at a steady temperature, allowing the system to maintain warmth without overworking. Many households transitioning from a gas boiler approach find this difficult to adjust to and end up with higher bills because they are running the system in the wrong way.

Hot water production

Producing hot water with an air source heat pump can also add to running costs. Heating water to high temperatures requires more energy, particularly if the system is set above 50 to 55 degrees Celsius. Some households notice higher bills if they run frequent baths or showers, or if the cylinder is set to reheat water too often. Adjusting hot water schedules, insulating the cylinder, and keeping the thermostat at an efficient level can reduce unnecessary electricity use.

Maintenance and servicing

Like any heating system, heat pumps require regular maintenance to operate efficiently. Dirty filters, blocked airflow, or refrigerant issues can all cause the pump to consume more electricity than necessary. If your heat pump has not been serviced recently, running costs may rise simply because the system is not performing at its best. Annual servicing by a qualified technician ensures that the pump continues to deliver efficiency and reliability.

Comparing costs fairly

It is important to compare heat pump running costs fairly against traditional systems. While a gas boiler may appear cheaper to run because gas prices are lower, heat pumps are more efficient and have lower carbon emissions. They may also qualify for government incentives that offset installation costs. Over the long term, a well-designed system in an insulated home should provide competitive running costs, especially as the UK electricity grid continues to decarbonise and renewable generation expands.

Conclusion

If your air source heat pump feels expensive to run, the cause is often a mix of insulation quality, installation design, user behaviour, and tariff choice. Unlike boilers, heat pumps require a different approach to heating, one that values consistency and efficiency over rapid bursts of heat. By making sure your home is well insulated, your system is properly designed, and your electricity tariff is competitive, you can bring costs down and enjoy the full benefits of renewable heating. Regular servicing and careful control of hot water schedules will also help to manage expenses. While upfront costs may feel high, an air source heat pump remains one of the most sustainable choices for long-term home heating in the UK.