Air Source Heat Pump Systems

What Is an Air Source Heat Pump System?

An air source heat pump (ASHP) is a renewable heating system that extracts heat from the outside air to warm your home and provide hot water. Even when temperatures drop below freezing, ASHPs can efficiently extract heat energy from the ambient air. The system works by absorbing heat from the outside air into a liquid refrigerant, which is then compressed to increase its temperature before being transferred to your central heating and hot water system.

Modern air source heat pumps can achieve efficiencies of 300-400%, meaning for every 1kW of electricity used, the system produces 3-4kW of heat. This makes them significantly more efficient than traditional gas or oil boilers, which typically operate at 85-95% efficiency.

Types of Air Source Heat Pump Systems

There are two main types of ASHP systems: air-to-water and air-to-air. Air-to-water heat pumps are the most common in the UK, distributing heat through your existing wet central heating system via radiators or underfloor heating. They also provide domestic hot water, making them a complete replacement for your existing boiler.

Air-to-air heat pumps distribute warm air directly through fans and ductwork. While they're excellent for heating, they don't provide hot water, so you'd need a separate system for that. However, they have the advantage of also providing cooling in summer, acting as a complete climate control solution.

Running Costs and Savings

Air source heat pumps typically cost between 4-6p per kWh to run, compared to 7-8p for gas and 10-12p for oil. For an average UK home, this translates to annual heating costs of £500-£800, compared to £800-£1,200 for gas and £1,200-£1,800 for oil.

With the £7,500 Boiler Upgrade Scheme grant and potential energy savings of £300-£600 per year, most homeowners see a payback period of 7-12 years. After this, the system provides essentially free heating for the remainder of its 20-25 year lifespan.

Installation Process

Installation of an ASHP typically takes 2-3 days and involves mounting the outdoor unit, connecting it to your heating system, and commissioning the controls. The outdoor unit needs to be placed on a solid base with adequate airflow, typically at least 300mm from any walls.

Before installation, a qualified installer will carry out a detailed heat loss survey to correctly size the system for your property. This ensures optimal efficiency and comfort. All installations should be carried out by MCS-certified installers to qualify for the Boiler Upgrade Scheme grant.

Environmental Benefits

By switching from a gas boiler to an air source heat pump, a typical UK household can reduce carbon emissions by 2-3 tonnes per year. As the UK electricity grid continues to decarbonise, this saving will increase further over time.

Heat pumps produce zero direct emissions at the point of use, unlike gas and oil boilers. Combined with solar panels and a green electricity tariff, you can achieve near-zero carbon heating for your home.