What is an Air-to-Water heat pump?
A heat pump captures heat from outside and moves it into your home. It uses electricity to do this, but the heat energy delivered to your home is more than the electrical energy used to power the system.
Electricity is becoming increasingly low carbon, as more renewable sources are connected to the electricity grid, replacing existing gas and coal power stations. This makes a heat pump an extremely low carbon heating option, and increasingly so as our electricity grid further decarbonises.
Heat pumps are suitable for many homes and may also reduce your energy bills, depending on the system you are replacing.
Tens of thousands of heat pumps have already been installed across the UK, and over 1.5 million heat pumps were installed across Europe in 2020 alone. The UK Government expects that millions of heat pumps will need to be installed in homes over the next 10-15 years to meet our net zero targets.
Air-to-water heat pumps
An air-to-water heat pump transfers heat from the outside air to water, which heats your radiators or underfloor heating. It can also heat water stored in a hot water cylinder for your hot taps, showers and baths.
Heat from the air is absorbed into a fluid. This fluid then passes through a heat exchanger into the heat pump, which raises the temperature and then transfers that heat to water.
Is an air-to-water heat pump right for me?
Air-to-water heat pumps are suitable for many types of homes and are the most common type of domestic heat pump, with tens of thousands of installations across the UK. However, there are a few things you should consider before deciding whether a heat pump is right for you.
Do you have somewhere to put it?
You’ll need a place outside your home where a unit can be fitted to a wall or placed on the ground. It must have some space around it to allow a good flow of air.
There are two types of air-to-water heat pumps: monobloc and split systems. A monobloc system has all the components in a single outdoor unit, with pipes carrying water to the central heating system and a hot water cylinder inside your home. A split system separates the components between indoor and outdoor units. Whether a monobloc or split system is right for you will depend on your budget and the space available.
Monobloc systems tend to be cheaper and quicker to install and don’t take up as much space in your home, although they are generally slightly less efficient than split systems. The efficiency gain from split systems comes from some of the heat transfer taking place inside the building where it is warmer, rather than outside.
If you’re not limited by space inside your home, it may be worth the extra cost of installing a split system. Your installer should be able to talk you through your options and help you choose the design that works best for you.
How Loud is a heat pump?
The external unit for a heat pump is identical for both monobloc and split heat pumps. Noise is created by large fans moving air across the heat exchanger.
Unless the heat pump is working very hard (ie in cold weather or producing high temperature water), you can expect the noise to be a similar volume to a fridge, if you were standing within a couple of metres. You could easily hold a normal conversation next to it, without raising your voice. As it gets colder outside, this noise will increase in volume while it’s operating, but should still allow you to hold a conversation easily, only raising your voice a little.
The inside unit for a split system only contains valves and pumps and makes very little noise at all.
How will you heat the rooms in your home?
Most homes in the UK use radiators or underfloor heating to circulate hot water – this is referred to as a ‘wet’ system. Air-to-water heat pumps need a wet system.
If you don’t currently have a wet system, you will have to decide whether you’d like to install one. This is a great opportunity to make sure the wet system is optimised for a heat pump, resulting in lower running costs.
Do you have a hot water cylinder?
A standard heat pump can’t provide hot water on demand like a combi boiler, so you will need a way of storing hot water for when you need it. The size of hot water cylinder required will depend on the amount of hot water that your household typically uses, but the cylinder can usually be fitted inside any cupboard that measures around 80x80cm.
If you don’t have space for a hot water cylinder, you still have options. Some hybrid systems are designed with the heat pump providing heating and a boiler providing hot water on demand. You could also consider installing a heat battery, which takes up less space than a hot water cylinder. Instantaneous hot water heaters are also available and can be installed under your kitchen sink to provide a smaller amount of hot water.
How much does an air-to-water heat pump cost?
The cost of an air-to-water heat pump varies depending on the brand, model and size of heat pump, the size of the property, whether it’s a newbuild or an existing property, as well as whether you need to change the way you distribute heat around your property. Typical costs are around £7,000 to £13,000, and we recommend speaking to at least three installers to provide a quote for your heat pump system to give you the best idea of likely costs for your home.
Will a heat pump save me money on my energy bill?
Running costs will depend on how your heat pump is designed and how it is operated. Savings on your energy bill will also be affected by the system you are replacing.