By Julie Curnow

Heat Pump Hot Water Reliability

Heat pump water heaters are relatively complex compared to other water heaters. This means that there is a variety of designs, energy efficiency and performance in available heat pump water heaters. Compared to a few years ago, heat pumps in today’s market are considerably more energy efficient. In general, heat pump water heaters are reliable if you choose the right system for your needs and taking measures to improve performance.

Heat pumps in colder climates

In the past heat pumps have been criticised for their inability to handle colder temperatures. However, innovators have today integrated new technologies into the systems to improve the reliability of heat pumps in colder climates. This along with other new integrations have improved the reliability of heat pumps.

If you live in a climate where frost is present in the colder months, you may experience performance issues with your heat pump. This is because high levels of moisture in the air on frosty days can hinder the evaporator’s heat transfer efficiency. For those who live in colder climates it is a good idea to invest in a system that is designed to handle these conditions. Some heat pumps, for example, have sub systems built into them that detect or predict the formation of frost and heat the evaporator coil to remove frost by reversing refrigerant flow periodically. Other heat pumps have an electric back up element that heats the water instead of the heat pump when the outside temperature is low.

Sacrificial anode replacement

Heat pumps contain a sacrificial anode that needs replacing every 2 to 5 years. If this is not done the tank life and thus the heat pump life will be shortened.

Find a balance between reliability and energy efficiency

Another factor which may impact the reliability of your heat pump is taking measures to improve energy efficiency. If you focus too much on energy efficiency you may compromise the performance of your heat pump. While reliability and energy efficiency are both significant factors when purchasing and installing a heat pump, you need to find a balance between them. You may, for example, achieve greater energy efficiency at the cost of a slower heat up time.

Use a timer

In some cases, using a timer can reduce the time spent heating the hot water to the required temperature. This reduces the hours the compressor has to work and can thus potentially maximise the life of the heat pump water heater.

If you are going away

If you are going away you can safely switch your heat pump off. If it has been left on for longer than two weeks without drawing hot water, you should open a tap to run your hot water for a few minutes to release a small amount of hydrogen gas that might have built up in the tank. Make sure there is no flame or electrical spark nearby that could ignite the gas.

The stored water may cool below 60 degrees Celsius while you are away. When you return, the water in the storage tank must be boosted to 60 degrees Celsius for 35 minutes before any hot water is used to kill any bacteria that may have grown. It could take several hours for the water to heat. Again reduced use will reduce the demand on the unit but the impact would be negligible over the life of the heat pump water heater.


To ensure your heat pump water heater will be reliable you should talk to the professionals and gather as much information as possible. This will reduce your risk of purchasing a product that underperforms because it isn’t right for your needs.


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