Heat Pump hot water systems have really come of age in the past few years after a very rocky start here in Australia that has left a lot of people vowing to never have another. This is a shame as this type of water heating is incredibly cheap, saving people a whopping 75% compared to a electric or LPG gas systems.  Like everything in this world, you get what you pay for and going for a no name cheap heat pump system will generally give you exactly what you have paid for, cheaper heat pumps can only be achieved if it is made cheaply with inferior parts and products use

During the mid to late 2000’s right through to 2015 many of the major hot water brands had heat pump products that were frankly nothing short of junk. When the government had solar and heat pump rebates around when changing from an electric water over and then they brought in regulations that new homes could only have solar, gas or heat pump hot water systems in a attempt to phase out the old electric style water heaters the rush to design and produce saw them make some very poor design decisions that defied any form of logic and commonsense that an engineer in charge of the research and development for hot water manufactures should even have considered.

Even still today unfortunately there are some very bad heat pump systems that are being sold to unsuspecting consumers by sales companies that are just there to sell as much as they can and some very poor cheaper no name Chinese and other imported Heat Pumps that just do not stand up to the Australian climate with the products they are made from exist

But if you are smart and understand that a cheaper product generally means it is made from cheaper components. Mind you the cost between the cheap the “no name” heat pump hot water heaters and a reputable brand manufacturer is really not that great and the electricity savings are massive to make the switch from a gas or electrical water heater to a heat pump when its time for a new hot water service.

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Below I will get into how heat pumps work and some of the different heating styles.  The easiest way to digest how  heat pump works is how a refrigerator cools and expels hot air a heat pump heats and expels the colder air, you know when you walk past a air conditioner when its running how hot air is blowing out the fan, a heat pump water heater blows out cold air and uses the hot air to heat the water via heating plates and pipes that wrap or are internal in the water storage tank. A heat pump uses 1kw of power to what a electric system uses 4kw, yes that’s 75% less power

Heat pump hot water heaters absorb warmth from the air and transfer it to heat water. This is why they are also referred to as ‘air sourced solar hot water heaters’.  They operate on electricity but are roughly three times more efficient than your standard element type conventional electric water heater. When used in the right environment they save energy, save money and reduce greenhouse gas emissions and when you have solar PV on your home will work very well together as they use a lower amount of power (generally around the 1kw mark as opposed to 3.6kw in a standard electric water heater)

How does a Heat Pump work?

A heat pump works on the same principle as a air conditioner or refrigerator, but instead of pumping heat out of the fridge or air conditioner to keep it cool, they pump heat into the water via pipes  submerged or wrapping storage tanks. Some brands also move the water from the tank through a heating plate to heat the water then back to the storage tank. Electricity is used to pump a refrigerant through the system. The refrigerant transfers the heat absorbed through the air to the water in the tank.

Heat pumps work through the use of a refrigerant that evaporates at low temperatures.

There are several steps in the process:

• A liquid refrigerant passes through an evaporator where it picks up heat from the air and becomes a gas.
• The gas refrigerant is compressed in an electric compressor. Compressing the gas causes its temperature to increase so that it becomes hotter than the water in the tank.
• The hot gas flows into a condenser, where it passes its heat to the water and turns back into a liquid.
• The liquid refrigerant then flows into an expansion valve where its pressure is reduced, allowing it to cool and enter the evaporator to repeat the cycle.

A heat pump uses electricity to drive the compressor and the fan instead, unlike a traditional electric resistance water heater that uses electricity to directly heat the water. The heat pump is able to transfer a much greater amount of heat energy from the surrounding air to the water, which makes it highly efficient. The amount of heat that is able to be transferred from the air to water depends on the ambient temperature.

While the outside “ambient” temperature is higher than the cold refrigerant gas, the heat pump will absorb heat and move it to the water. The warmer the outside temperature, the easier and more efficient it is for the heat pump to provide hot water. As the outside temperature decreases, less heat can be transferred, which is why heat pumps don’t work as well in places where temperatures are low. A few heat pump manufacture’s now make systems that work down in the negative temperatures which means some may be installed internally where there is enough space, the size of a large garage with some ventilation

In order for the evaporator to allow heat to be absorbed continuously, there needs to be a constant supply of fresh air. A fan is used to force air flow through and the colder air is removed to the atmosphere

Heat pump water heaters are available in two different styles

• Integrated or compact design where the compressor and the storage tank are a single complete system
• Split systems: the tank and the compressor are 2 separate items, like a split air conditioner, where the storage tank is connected to the  heat pump component by refrigerate pipes