Heat Pump Hot Water Cylinders
Heat pump hot water cylinders are specifically designed to work efficiently with air source and ground source heat pumps, providing reliable domestic hot water (DHW) storage at the lower flow temperatures typically associated with heat pump systems. Compared with a standard boiler cylinder, a heat pump cylinder normally uses a much larger heat exchanger coil to improve heat transfer and reduce recovery times.
They are suitable for homes, flats, apartments and commercial properties where a heat pump is being used to produce stored hot water.
Select a cylinder below to view its dedicated product page, technical information and specifications.
What Is a Heat Pump Hot Water Cylinder?
A heat pump hot water cylinder is an insulated storage vessel designed to store potable hot water and to receive heat from a heat pump system.
Unlike a conventional boiler, a heat pump generally operates most efficiently at lower water temperatures. This means the cylinder requires a larger coil surface area to transfer sufficient heat from the primary heating circuit into the stored domestic hot water.
A typical heat pump cylinder can include:
- Large surface-area heat exchanger coil
- High-performance insulation
- Immersion heater connection
- Temperature sensor pockets
- Cold water inlet
- Hot water outlet
- Tundish and safety controls on unvented systems
- Temperature and pressure protection
- Drain connection
The exact configuration will depend on whether the cylinder is vented or unvented and whether additional heat sources such as solar thermal are required.
Why Do Heat Pumps Need a Different Hot Water Cylinder?
The main difference is the heat exchanger coil size.
Traditional gas or oil boilers can often supply primary water at relatively high temperatures, allowing a smaller coil to transfer sufficient heat.
An air source heat pump typically operates at lower flow temperatures to maintain a high Coefficient of Performance, or COP. A larger coil provides the heat pump with more surface area to transfer energy into the stored water.
Using an unsuitable cylinder with a small coil can lead to:
- Slow hot water recovery
- Longer compressor operating periods
- Reduced heat transfer
- Lower system efficiency
- Difficulty reaching the required cylinder temperature
For this reason, the cylinder should be selected specifically for the output and operating temperatures of the heat pump.
Unvented Heat Pump Cylinders
Many UK heat pump installations use an unvented hot water cylinder.
An unvented heat pump cylinder is connected directly to the mains cold water supply and can provide high-pressure hot water to showers, baths and taps without requiring a cold water storage tank in the loft.
These systems must incorporate the required safety devices and be installed in accordance with UK Building Regulations, including the requirements applicable to unvented hot water storage systems.
Correct sizing is also important because the cylinder needs to provide enough usable hot water while allowing the heat pump sufficient time to recover the stored volume.
What Size Heat Pump Hot Water Cylinder Do I Need?
Heat pump cylinder sizing should be based on more than just the number of bedrooms.
Important factors include:
- Number of occupants
- Daily hot water demand
- Number of showers and baths
- Shower flow rates
- Cylinder storage temperature
- Heat pump output
- Coil performance
- Recovery time
- Peak hot water usage
Because heat pumps can have slower recovery rates than traditional boilers, sufficient stored water capacity is particularly important.
A larger cylinder can often allow the heat pump to operate efficiently for longer periods while reducing reliance on an electric immersion heater for boosting.
Heat Pump Cylinder Efficiency
A well-designed heat pump hot water cylinder improves overall system efficiency by maximising heat transfer and minimising standing heat losses.
High-quality insulation reduces the amount of stored energy lost from the cylinder, while an appropriately sized heat exchanger helps the heat pump operate at lower and more efficient flow temperatures.
The cylinder should therefore be considered an important part of the complete heat pump system rather than simply a hot water storage tank.
Heat Pump Hot Water Cylinders for UK Properties
Our range of heat pump hot water cylinders is suitable for domestic and commercial heat pump applications where efficient hot water storage, excellent recovery performance and compatibility with low-temperature heating systems are required.
Choosing the correct cylinder involves matching the storage volume, coil output, heat pump capacity and expected domestic hot water demand to the individual property.