Do Air Source Heat Pumps Heat Water

Air source heat pumps have become an increasingly popular choice for heating homes across the UK as households look for energy-efficient and sustainable alternatives to traditional boilers. They are often discussed in terms of providing heating through radiators or underfloor systems, but one of the most common questions asked by homeowners, landlords, and developers is whether air source heat pumps can also heat water for everyday use. The simple answer is yes, they can, but the way they do so and the level of efficiency depends on the system design and how it is installed.

How Air Source Heat Pumps Work

An air source heat pump operates by extracting heat from the outside air and transferring it into the home. Even when outdoor temperatures are low, the system can capture and upgrade ambient heat using a refrigerant cycle, much like a reverse refrigerator. This heat is then distributed around the property, typically through radiators or underfloor heating. A well-designed system can operate efficiently in most UK climates, although performance may vary depending on outside temperatures and property insulation levels.

Heating Water with an Air Source Heat Pump

Yes, air source heat pumps are capable of heating domestic hot water. Most systems are designed to connect to a hot water cylinder, where the heat pump raises the water temperature to a usable level for taps, showers, and baths. The process is similar to how a conventional boiler works with a cylinder, but instead of burning gas or oil, the heat pump uses electricity to transfer heat from the air. In many installations, a specialist hot water cylinder with a larger coil is required to ensure effective heat transfer from the pump.

Water Temperature Considerations

One important difference between air source heat pumps and traditional boilers is the maximum water temperature they can achieve. While gas and oil boilers can heat water to 70°C or more, air source heat pumps generally produce hot water at lower temperatures, often around 50°C to 55°C. This is perfectly adequate for most domestic uses, but it does mean that heating cycles may be longer and water storage is more important. To comply with UK building regulations and reduce the risk of legionella bacteria, systems are often fitted with an immersion heater that can raise the cylinder temperature to 60°C when required.

Efficiency of Water Heating

When it comes to efficiency, air source heat pumps can be more economical than direct electric heating and in many cases cheaper to run than gas or oil boilers. They work most efficiently when heating water to moderate rather than very high temperatures, which makes them well suited to modern well-insulated homes with low-flow showers and efficient taps. The coefficient of performance (COP) is an important measure of efficiency. For example, a COP of three means that for every unit of electricity used, three units of heat are delivered to the home or hot water cylinder. However, COP varies with outside temperature, so efficiency may drop during colder months.

Hot Water Storage and Demand

Because air source heat pumps operate most effectively at steady temperatures, they work best with hot water storage cylinders. This allows the system to gradually heat water and store it until required. In households with higher demand, such as families using multiple bathrooms, the size of the cylinder must be carefully matched to the needs of the property. Unlike combi boilers, which deliver hot water on demand, heat pumps rely on stored hot water. This means there is more planning involved, but when properly designed, the system can comfortably meet daily needs.

Integration with Other Systems

Air source heat pumps can be integrated with other heating solutions to improve hot water performance. In some properties, hybrid systems are installed, where a traditional boiler works alongside the heat pump to provide top-up heating when needed. In others, immersion heaters or solar thermal panels are used in combination with the pump to ensure sufficient hot water supply. These approaches allow households to balance efficiency with reliability, particularly in older properties or those with higher hot water requirements.

Cost Implications

The cost of heating water with an air source heat pump depends on installation and usage. While the upfront installation cost of a heat pump and hot water cylinder is higher than fitting a traditional boiler, running costs are usually lower if the system is designed correctly. The government has also introduced financial incentives through schemes such as the Boiler Upgrade Scheme, which helps offset initial investment. For landlords and property developers, the potential savings on running costs can make homes more attractive to tenants and buyers, particularly given growing awareness of energy efficiency.

Maintenance and Longevity

When it comes to hot water provision, air source heat pumps require regular maintenance to ensure efficiency. This includes checking the refrigerant cycle, cleaning filters, and ensuring the hot water cylinder operates correctly. The immersion heater, if fitted, should also be tested periodically. With proper care, a heat pump can last around 15 to 20 years, which is comparable to or longer than many traditional heating systems. This makes them a long-term investment for properties looking to reduce carbon emissions and running costs.

Building Regulations and Compliance

In the UK, any installation of an air source heat pump must comply with building regulations, particularly Part L, which deals with the conservation of fuel and power. Hot water systems connected to heat pumps must be designed to operate efficiently and to minimise energy loss through proper insulation of cylinders and pipework. Legionella risk management is also a regulatory requirement, which is why immersion heaters or other measures to boost water temperatures are included in system design. For landlords, compliance with regulations not only ensures safety but also demonstrates due diligence in meeting legal responsibilities.

Final Thoughts

So, do air source heat pumps heat water? Yes, they do, and when properly installed they can provide a reliable and efficient supply of hot water for everyday use. While they operate differently from traditional boilers and rely on lower water temperatures, they are capable of meeting domestic hot water needs in most UK households. With the right system design, appropriate cylinder size, and regular maintenance, an air source heat pump can be a cost-effective and environmentally friendly way to provide both heating and hot water.