Heat Pump Hot Water Cylinder

Heat Pump Hot Water Cylinder

Heat pumps work by moving existing heat from the air into your hot water cylinder. This cuts your energy bill by around 70% compared with gas tank-types.

They can run on the cheaper off-peak electricity tariff overnight if the cylinder is large enough. When the cylinder gets low on hot water, the electric coils take over.

Energy efficiency

Heat pump hot water cylinders use electricity to move rather than make heat, making them the most energy efficient way to heat your water. They consume up to three times less energy than resistive electric hot water tanks, and they don’t produce greenhouse gases.

The heat pump uses an insulated storage tank to store the heated water, but it draws energy from ambient air (or sometimes ground or water bodies) to heat the cylinder, rather than heating the cylinder directly using electric resistance elements. The system has a fan to pull in warm air, and the evaporator coils inside the cylinder absorb the warmth from the surrounding air. The refrigerant then pumps the warm water into the compressor, where it’s compressed and heated, before it reaches the evaporator again, which releases the heat into the cylinder.

Some models are able to take advantage of cheaper night-rate electricity, which can significantly reduce the operating cost. Check with your electricity supplier to see if this is available in your area.

You’ll also want to consider the energy factor of any HPWHs you’re considering, which is a number based on heat pump hot water cylinder how much hot water your heater can produce per unit of power used over a day. The higher the energy factor, the more efficient your HPWH is. Here at Elephant Energy, we only install HPWHs with an energy factor of over 2, since they’re the most sustainable and lowest overall cost options.


A heat pump hot water cylinder absorbs heat from the air, ground or water bodies and then uses a compressor to raise the temperature of the stored water in an insulated cylinder. The system is more energy efficient than a traditional electric storage tank and can operate in areas that aren’t suitable for solar water heaters. However, the electricity consumption of a heat pump water heater is more variable than that of a standard storage system, and operating costs will depend on your daily water usage patterns and the time of day you use it.

Like all hot water systems, heat pump cylinders lose some heat through the cylinder walls when they’re not being used. This is known as “standing losses” and contributes a significant proportion of total hot water energy consumption. To minimise these losses, you can reduce your electricity use by using a timer to restrict your water heating to the middle of the day when cheaper night-rate electricity is available.

As with any electrical appliance, heat pump cylinders can produce a fair amount of noise during operation (about the same as an outdoor air conditioner). They should be installed away from bedrooms and other living areas and in a well-ventilated location. When removing your old water heater, make sure to save the temperature and pressure relief valve plumbing and the electrical wire nuts for reinstallation on the new tank.


As with any other type of water heater, a heat pump water heater needs regular maintenance to ensure it continues to operate efficiently. Some of the main tasks involved include draining any sediment from the bottom of the tank, replacing a sacrificial anode or switching to a powered anode (which can help prevent copper and lead contamination in your hot water), and cleaning the air filter on the heat pump unit.

The external heat pump unit should be checked to ensure it’s securely connected to the ground (or to a wall if it’s wall-mounted) and that any anti-vibration mounts are effective. Also, a technician can top up refrigerant levels, or replace the refrigerant altogether, as needed.

During an annual maintenance visit, a technician can check that the power is off and that the access panel is removed to allow inspection of the inside of the heat pump unit. Also, the unit’s air connections should be inspected to ensure they are correctly connected.

Most newer heat pumps are equipped with a display screen and diagnostic system that make problem diagnosis a breeze. These will show error codes when something goes wrong, and a technician can quickly determine the cause of the problem (e.g., a faulty heating element, dirty air filter, or sensor malfunction). If your heat pump is giving an error code, you should disconnect it for some time simply (the exact length of time depends on the model), then resume power to see if the error persists.


The manufacturer warranty for a heat pump hot water system can be confusing and lengthy. Often it will involve time on the phone with their warranty department and collaboration with your plumber. A good technician heat pump hot water cylinder will spend the time needed to get the right information and ensure the process is a smooth one for you.

The warranty covers the unit and the cylinder. The cylinder warranty is either 6 or 10 years depending on the model chosen and the application. It is reduced to two years in a commercial or multi-family domestic setting.

It does not cover the ancillary plumbing such as isolation valves, non-return valves, electrical switches, pumps or fuses. It also does not cover the venting which must be sized correctly for the application.

Another consideration is standing losses which all storage systems have. These losses are a proportion of the total energy use. For small households these can be a large portion of your energy use. Using an efficient system will help minimise these losses.

A heat pump system can be eligible for energy efficiency incentives from state and territory schemes. This can save you a lot of money. These schemes will differ between states, so make sure you check out what is available in your state.