How long does a heat pump take to heat water?

Key takeaways:

• Heat pumps heat water by efficiently transferring heat from outdoor air and have the ability to continuously heat water so you never go without
• While heat pumps produce lower temperature water, it’s still high enough to meet hot water needs
• During those rare periods of exceptionally high use, you have the option to make extra hot water

Heat pumps are known for their energy efficiency and are becoming increasingly popular for water and space heating. They work by transferring heat rather than generating it, providing an eco-friendly alternative to traditional systems like boilers. But you may be wondering if you’ll be left waiting a long time for fresh shower water.

How do heat pumps heat water?

Heat pumps transfer heat from ambient air to water by using a refrigerant cycle that absorbs heat from the air, compresses it to increase the temperature, and then transfers it to the water through a heat exchanger. This process achieves efficiency rates over 400%, or about four times more than gas boilers. Home air source heat pumps can reach temperatures of 35-55°C for heating and around 55-60°C for hot water use, making them ideal for homes with good insulation and low heating needs.

Factors affecting heating time

Several factors influence how quickly a heat pump heats water:

1. Target Temperature: Higher temperatures require more time.
2. Pump Efficiency: Heat pump models vary in performance; more efficient models work faster.
3. Ambient Temperature: Colder air reduces heating speed, as more energy is needed to achieve the desired warmth.

Efficiency & size

Heat pumps provide over 4 kWh of heat per 1 kWh of electricity, far surpassing traditional systems like gas boilers with an efficiency of around 90%. To maximise efficiency, pair a heat pump with an appropriate water cylinder and insulation. Heat pump cylinders include larger coils to better capture the pump’s lower heat output, ensuring ample hot water supply.

Accurate wattage of the pump and the size of the cylinder are also essential for efficiency. An outdoor heat pump unit typically measures about 1m x 1m x 2m, while the hot water tank should ideally be 2m x 1m x 1m. Proper sizing helps optimise heating, and heat-pump-specific cylinders help maintain hot water on demand.

Heating timelines

Hot water heating time from cold depends on many factors, like the wattage of your heat pump and the size of your hot water tank. For example, if you have a smaller system with a 6 kWh heat pump and a 100 litre hot water tank, it will take 50 minutes for your tank to reheat from cold. With a larger system, like a 12 kWh heat pump and a 300 litre tank, the reheat time from cold is 74 minutes. Keep in mind, however, that your system will start reheating hot water almost as soon as you begin using is, making it rare to runout.

Heat pumps reach 45-50°C comfortably, but it may take extra time to reach the storage-safe temperature of 55-60°C. For those special occasions when you need more hot water, the Aira Home Energy app gives you the option to make extra hot water to meet all your needs.

Tips to optimise heating

1. Limit heating sessions: Schedule water heating for 3-4 brief sessions daily, especially during low-demand hours and combine with a heat pump tariff like Cosy Octopus to heat your hot water at lower prices.
2. Temperature settings: In the Aira Home Energy app, you can choose between three different heating setting to meet your needs — Eco saver (42°C), Standard (52°C), and Luxe (62°C). The warmer the tank temperature, the more hot water you have available at any given time.
3. Making more hot water: Your Aira Heat Pump will learn your hot water needs over time so you always have enough. But on those special occasions when you really need more, it is possible to make more from the Aira Home Energy app. Keep in mind that using this feature will also use more energy, reducing the efficiency and energy savings of your pump. If you find yourself frequently needing more hot water, consider adjusting your tank temperature.

Conclusion

A heat pump is an efficient, eco-friendly solution for home water heating that effectively balances comfort and savings, especially with a well-planned system and optimised settings.