Can an Air Source Heat Pump Be Used for Hot Water Only?

Can an Air Source Heat Pump Be Used for Hot Water Only? Yes – an air source heat pump can quite happily just be used to make hot water, without bothering with any space heating at all. These systems are quite commonly known as heat pump water heaters or DHW heat pumps. They grab heat from the air outside and transfer it into a hot water cylinder that’s stored in your home, giving you a way to have hot water without having to rely on an electric immersion heater that’s burning cash.

How does a hot water only heat pump work?

A dedicated air source heat pump water heater works using the same basic idea as a bigger heat pump.

A fan sucks in some air and passes it across an evaporator that’s got some refrigerant inside. This refrigerant absorbs the heat from the air before it gets pumped through a compressor, which squishes it and heats it up.

This heat then gets transferred over into the domestic hot water.

The main difference is that a dedicated water heater is designed just for making hot water. It doesn’t have to do any heating of radiators or underfloor heating.

This makes it a pretty useful option where the property has already got another heating system installed but you want a more efficient way of producing hot water.

For lower-volume hot water requirements, our 100 litre wall mounted heat pump DHW heater offers a compact solution suitable for many smaller properties.

For increased residential capacity, see our 200 litre heat pump DHW heater or 300 litre heat pump DHW heater.

For high-demand installations, explore the 400 litre commercial heat pump DHW heater or 500 litre commercial heat pump DHW heater.

What is an integrated heat pump water heater?

One of the most common ways to use an air source heat pump for just hot water is an integrated heat pump water heater.

This is basically a system that combines the heat pump and hot water cylinder all into one device. The compressor, evaporator, fan, refrigerant circuit and cylinder are all designed to work together seamlessly.

From the outside, these things look a lot like a big, tall hot water cylinder, with the heat pump bits at the top.

Because the whole thing is designed specifically for making domestic hot water, you often don’t need a separate heat pump unit outside.

Can you use a separate heat pump with a hot water cylinder?

Yeah, you can. A dedicated external air source heat pump can be connected to a suitable heat pump hot water cylinder.

With this setup, the heat pump heats some primary water, which is then circulated through a heat exchanger coil that’s inside the cylinder. Heat from the primary water gets transferred over into the stored hot water.

The cylinder needs to be properly matched up to the heat pump, though.

Heat pumps generally run at lower temperatures than traditional boilers, so the heat exchanger coil needs to be a bit bigger to transfer the heat effectively at those lower temperatures.

Is a hot water heat pump more efficient than an immersion heater?

Generally, yes, and that’s one of the big reasons to use one.

An electric immersion heater uses up electricity and just burns some cash – 1 kWh of electricity is 1 kWh of heat, right there at the point of use.

A heat pump takes heat that’s already in the air and moves it over into your hot water.

If a heat pump water heater is working at a Coefficient of Performance (COP) of 3, for instance, it could give you around 3 kWh of useful heat from every 1 kWh of electricity it uses.

But actual efficiency is going to depend on air temperature, incoming cold water temperature, the temperature you need the hot water to be, and the design of the heat pump.

Can a hot water heat pump reach 60°C?

It depends on the model you get.

Some units are designed to make pretty hot water using just the compressor, like some newer R290 heat pump water heaters that use refrigerant-grade propane.

Others may get the water up to a good temperature, then use an immersion heater if you need a higher temperature for something, like a thermal disinfection cycle.

You should check the maximum water temperature and how well the unit performs at that temperature when you’re comparing different models.

Just because a unit can make hot water at a high temperature, it doesn’t mean it should be running at that temperature all the time. Heat pumps usually work a bit better when the required water temperature is a bit lower.

Where can a hot water only heat pump be installed?

These integrated systems are often installed in places like utility rooms, garages, plant rooms and other areas that are meant to take care of the behind-the-scenes stuff.

The appliance needs to be in a spot where it can get a good flow of air to grab heat effectively. Some models can just use air from the room, while others might need ducting to pull in air from elsewhere.

You’ve also got to account for condensate drainage, as there’s a bit of moisture in the air that can condense on the cold evaporator when it’s working.

Fan and compressor noise is also a thing to consider when choosing a spot to put the thing.

Who might use a hot water only air source heat pump?

If you already have another system for space heating, a dedicated hot water heat pump can be a great option.

For example, a property might keep a gas boiler, electric heating, biomass system or another heating source for the main space heating while using a heat pump to make domestic hot water.

It can also be a good option if you are replacing a direct electric hot water cylinder, because the heat pump can reduce the electricity you need to use to get the same quantity of hot water. Solar PV can complement this setup by using some of that air source heat pumps electricity to be powered by electricity generated right on site.

Do you really need a full air source heat pump system just to heat the water in your house?

No, if you only want to knock out hot water, you don’t necessarily need a whole-house air source heat pump which is designed to do the job of a radiator or underfloor heating system for the whole house.

A dedicated heat pump water heater can produce hot water independently of whatever system is used to heat the rest of the house. Depending on the situation, this might be one single unit with the cylinder and heat pump all in one, or it could be a separate DHW heat pump thats connected up to a suitable cylinder.

The key things to consider are how much hot water you need, how long it takes to heat it back up, what temperature you need to get it to, how efficient it needs to be, where the air source is and where exactly the heat pump is going to be installed. If you get it all right, a heat pump can provide an efficient solution just for hot water without having to change the way the rest of your house is heated.