Can an Air Source Heat Pump Heat Water to 60°C?

Can an Air Source Heat Pump Heat Water to 60°C? Yes, it can, but it depends on the model, the refrigerant it uses and how it’s set up. Air source heat pumps can heat your domestic hot water to 60°C, but it’s not always that simple. Many standard air source heat pumps do the job pretty well at getting hot water up to around 50-55°C, and then they use electric immersion heaters to bump it up to 60°C when you need it. But newer high-temperature heat pumps, especially some using R290 propane refrigerant, can actually get the water to 60°C on their own without needing an immersion heater.

How does an air source heat pump get water to 60°C?

An air source heat pump extracts heat from the air using an evaporator. This heat is then absorbed by a refrigerant that passes through a compressor and gets turned up in pressure and temperature. The hot refrigerant then transfers its energy through a condenser or heat exchanger to the water that’s in the hot water cylinder.

In a typical air-to-water system, the heated water flows through the coil in the hot water cylinder, transferring heat to the water stored in the cylinder. In a dedicated heat pump water heater, it works on the same basic principle but is designed to make hot water, not just heat your living spaces.

In the UK, the Energy Technology List actually recognises air-to-domestic hot water heat pumps as a special type of electrically driven refrigeration system that’s designed to take heat from the outside air and put it into your hot water system.

Find further information about our air source heat pump hot water systems through the following dedicated pages:

Wall mounted heat pump hot water heaters
Domestic heat pump hot water heaters
Commercial heat pump hot water heaters

Do all heat pumps get to 60°C without an immersion heater?

No, and that’s a pretty important thing to know when you’re comparing different heat pumps.

Lots of heat pumps are designed to make hot water at around 50-55°C, and if your cylinder needs to get up to 60°C or higher, then the system will probably turn on its immersion or booster heater to get the job done. But other heat pumps are designed specifically to get hotter – some up to 70 or even 75°C – and can manage it without an immersion heater.

The R290 heat pumps are particularly interesting here. R290 is a type of propane that’s specially designed for use in refrigeration and has some properties that make it great for higher-temperature applications. Some current R290 heat pumps can heat water in the pipes to 70 or 75°C, though the maximum temperature depends on the outside conditions and the specific model.

That means that getting to 60°C is well within the range of some of the newer high-temperature heat pumps.

Does heating water to 60°C make a heat pump less efficient?

Mostly yes, it does.

A heat pump has to work a lot harder because the difference between the temperature it needs to heat the water to and the outside air temperature gets bigger. This is often called the temperature lift. So if you’re trying to get water to 60°C when the outside air is 10°C, that’s a bigger lift than if you’re trying to get it to 45°C.

As the water needs to get hotter, the heat pump’s efficiency will usually go down, and that means it’ll use more electricity to make the same amount of heat.

So while you can get a heat pump to make 60°C water, it’s not necessarily the most cost-effective way to run it all the time.

Why would you need domestic hot water at 60°C?

One pretty important reason is Legionella control.

Lots of heat pump systems include a system for sterilising the water and getting rid of any bacteria that might be growing in the system. Some heat pumps will do this by getting the water up to a really high temperature – over 60°C – and then just letting it cool back down again. Other systems that are designed to work most efficiently at around 50-55°C may need to use an immersion heater to get the water up to 60°C for this sort of thing.

You should be careful to make sure you’ve got the right temperature and Legionella control strategy for your type of property and that it’s in line with the manufacturer’s instructions and the rules for water hygiene in your area.

Can an R290 heat pump get hot water to 60°C more efficiently?

Maybe, but it’s not that simple.

R290 has a very low global warming potential and is used in some high-temperature air source heat pumps, and some of these can get water to even higher temperatures than 60°C. The efficiency of a heat pump depends on several factors, including outside temperature, inlet water temperature, compressor design, heat exchanger performance, and heat transfer effectiveness.

Just because a heat pump can make water to 70 or 75°C doesn’t mean it should always be doing that.

Can you get 60°C water in a UK home?

Yes, you can, with the right air source heat pump system. The key thing is whether the particular heat pump you’re using can get to 60°C through the refrigeration cycle alone or whether it needs a bit of help from an immersion heater.

When you’re comparing different systems, make sure you check the manufacturer’s maximum possible water outlet temperature, what temperatures the system is designed to work at, how well it does at making hot water, its efficiency, and how it does at low outside temperatures. For domestic hot water jobs, the goal shouldn’t just be to pick a heat pump that can crank out the highest temperature. A properly designed system needs to strike a balance between hot water temperature, keeping Legionella in check, cylinder capacity, how long it takes to recover hot water and how efficient it is with electricity in order to give you reliable hot water, all while keeping your electricity bills as low as possible.