What you need to know about your air source heat pump’s cylinder

An ASHP cylinder is specifically designed to work with the lower flow temperatures that a heat pump operates at. It does this by having a larger coil than would be used in a traditional boiler cylinder, allowing heat to be transferred faster to the water inside the cylinder even at lower temperatures. 

A heat pump provides a continuous supply of warmth to heat your home according to your selected temperature, using ambient heat from the outside air to do so. This same ambient heat is what is used to heat the water in your cylinder when required. 

An air source heat pump paired with a cylinder is a more efficient way of producing hot water when compared to a fossil fuel appliance. The system will be designed to maximise performance and deliver comfort for both your heating and hot water needs.

As is the case with standard hot water cylinders, space and location are key considerations for an ASHP cylinder. Most ASHP cylinders will be fitted in a utility room, airing cupboard, or loft. Your installer will consider any weight bearing and access requirements. If you need a cleaner, more compact, faster installation then a pre-plumbed, pre-wired cylinder may be a good option.

Another factor to consider is your typical heating and hot water usage. This will determine what capacity your cylinder needs to be, in order to meet these needs. Your installer will discuss your requirements with you as well as looking at the number of bathrooms and bedrooms. 

There are a wide range of cylinders available on the market. When speaking with your installer, please ensure it is set up for anti-legionella protection.

It is important when selecting an installer for an ASHP cylinder installation you confirm that they are G3 certified to safely commission and maintain unvented hot water systems in accordance with UK regulations.

An initial survey will be carried out as part of the heat pump design process, which will determine the specific cylinder that you’ll need for your property. You may also want to explore any grants that are available from your local authority or if you are eligible for support through incentives like the Boiler Upgrade Scheme.

Though a cylinder will be needed in the vast majority of cases, it may not be needed if you are using a hybrid system. This is where a heat pump works with a boiler or other alternative source to provide a flexible solution. 

For example, heating can be managed by the heat pump and hot water managed by a combi boiler. 

Hybrid systems essentially switch from one source to the other when temperatures drop below a certain level or in times of excessively high demand. This can help to optimise performance and potentially lower energy costs, depending on how the system is set up and your energy supplier. If you already have a combi boiler fitted, then you can continue using this for your hot water while the heat pump takes care of the heating requirements.

An important consideration is that hybrid systems are not eligible for grants such as the Boiler Upgrade Scheme (BUS).

An expert installer will work with you to assess your needs and your property’s specifications, so you can be sure that the solution is suitable for what you require. You can also start thinking about what steps you might need to take to get your home ready for a heat pump by using our checklist and guide, and look at any grants that might help you with the initial cost of the installation. 

See our full range of heat pumps and cylinders here.