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Air source heat pumps are going to be at the heart of the nation's sustainable future, so George Clarke explores the technology

Ok, be honest. Do you know what an air source heat pump is and how it works? No?

Well, I’m not surprised because very few people do. I didn’t really understand the technology myself until a few years ago.

At the moment heat pump sales per year in the UK are in their tens of thousands. Compare that to the gas boiler market, which currently sells around 1.5 million boilers per year and you realise that air source heat pumps are a tiny part of the market, but I promise you that is all about to change.

I’m writing this blog for one simple reason; to raise awareness of the benefits of air source heat pumps. If you don’t know about them why would you consider making any changes to your current heating and hot water system? Also, when you do know about them you might not believe how they work.

Ok, so awareness is one big issue, but another stumbling block to anyone buying an air source heat pump is that they can’t get their head around the technology. They don’t actually believe it. How can a unit take heat from the air to heat my house to say a temperature of 20 degrees Celsius when it’s only 5 degrees outside? It’s not going to work? Well, it does. Let me explain by starting at the beginning.

Air source heat pumps are a tiny part of the market, but I promise you that is all about to change.

George Clarke George Clarke Architect, TV presenter, writer and lecturer

Antiquated and carbon intensive

You currently have a gas or oil fired boiler. You know from your energy bills that burning these fossil fuels isn’t getting any cheaper and you are no doubt aware of the costs to the environment.

Not just the damage caused in extracting these base fossil fuels, but also the detrimental effect on the environment by burning them.

Let’s be honest, it isn’t the most sophisticated way of heating our homes, particularly when we know we are going to run out of the stuff at some point. The planet is a pretty amazing ecosystem and Mother Nature is very good at giving us what we need to survive. If we overuse or miss-use those resources then we are in trouble.

Mother Nature has given us the Sun and what a phenomenal resource that is.

But, some of us are so far behind the times we haven’t woken up to what the sun can actually do for us.

Do you know that more power from the Sun hits the Earth in a single hour than the entire population of the planet uses in an entire year! Yet, solar power only provided 0.39% of the energy used in the United States last year. How stupid is that? Globally, we only need to cover a land area the size of Spain in solar panels to power the earth in renewable energy.

Amazingly simple

There is also the heat held in the air that surrounds us. And this is also renewed every day when the sun rises.

Even on the coldest day, there is ‘heat’ from the sun and using an air source heat pump, we can capture that heat and use it to heat our homes. The technology is actually very straightforward, but the effect is amazing.

I’m about to have an ‘Ecodan’ air source heat pump fitted to my house, so this is something you can easily have installed on your existing property as well as a new-build home.

It’s basically a small box that sits outside your home and uses a fan to draw outside air across refrigerant piping.

Your fridge freezer uses a heat pump to basically remove the heat from inside your fridge box, ejecting it to the outside and therefore keeping your fridge cold. You’ll have noticed that sometimes there is a high level of heat around the back of your fridge, well that is the heat pump hard at work removing the heat from inside box.

By expanding and compressing the refrigerant inside the heat pump you can achieve even lower air temperatures, hence why your freezer can be so much colder than your fridge, even when it is sitting in a very warm kitchen.

By simply reversing this process using the same basic technology used in your fridge, an air source heat pump can take even the smallest amount of heat held within the outside air, compress it and upgrade it, to provide all the heating and hot water you need in your home.

An air source heat pump can extract heat efficiently from the outside air even when temperatures are as low as MINUS -10 degrees or more.

Yes, I know it’s virtually impossible to believe, but it’s true.

An air source heat pump is able to extract even the tiniest amount of heat from air when temperatures are sub-zero to heat your home. This is 100% true, hence why this opportunity for renewable energy is so good, for you, your home and the planet.

And the cost?

You’re now thinking, how much does all this cost? An air source heat pump installation costs more than a gas boiler. But, you need to see it as a completely different product.

An electric car might cost you more than a diesel car, but every person I know that drives an electric car says they wouldn’t go back because of the long term cost benefits to their wallet and the environment.

One guy recently said to me, “when I have to leave my electric car at home and drive a diesel or, say when I book a hire car when I’m abroad on holiday, I feel like I’ve gone back to the dark ages! I’ll never go back”.

Well you’ll be saying the same about your home air source heat pump.

The installation and capital cost obviously depends on the size of your house, the condition of the windows, levels of thermal insulation, the volume of space you need to heat, the number of bathrooms you have and the amount of water you have to heat etc etc.

You should get a specialist to come to your home to do all of the calculations and recommend the most appropriate type and size for you. But, as a very broad, general guide, to install an air source heat pump system into a standard 3/4 bedroom house with a main family bathroom and a small en-suite, will cost around £8,000 - or more if you need additional work (*).

Now, before you spit your tea out, it’s worth considering the benefits.

(*) Note from Editor: Before the cost of any preparatory upgrading that may be required to your home’s insulation (for example, if it requires the installation of additional, or different, radiators or improved insulation).Get several quotes from professional renewable heating installers.


You will see a considerable reduction in your energy bills. The heat from the air outside is free so you are only paying a relatively small electricity cost to actually power the heat pump unit. Spread that energy bill saving across the life of an air source heat pump installation cost and you're laughing.

The payback time from energy bill savings alone is around 7 years. The government is also giving out grants to promote this new technology. This is called a Renewable Heat Incentive (RHI) and the estimate average annual RHI payments for air source heat pumps are £1,259!

So yes, air source heat pumps cost a few quid to install. But, the combined savings from reduced energy bills and government incentive means you’re going to break even in no time and will then be getting free energy to heat your home and your hot water for many years to come.

Why wouldn’t you?

This is honestly not a sales pitch. It really isn’t. I care about home design and high levels of comfort, I worry about heating bills going through the roof for everyone, and yes I do worry about the terrible impact the running of our homes have on the environment.

This is fantastic, clean, green and affordable technology if you’re planning on staying in your home for the next few years. It is a brilliant opportunity for all of us, especially when it is so easy to install in your existing home.

And that is why I’ve decided to go for an installation myself with Mitsubishi Electric’s Ecodan Air Source Heat Pump, which is amazingly efficient and ultra quiet. Ecodan comes with really cool smart controls that allow you to monitor and control your heating from anywhere. Just what I need with my crazy schedule!

The Committee on Climate Change forecasts that heat pump heating will rise to over 1 million units per year, because the technology is so good and the financial benefits are so significant. It’s time for us all to move out of the dark ages and embrace renewable energy.

I’m proud to be one of those million people going for an air source heat pump and I hope you will be too.

There’s certainly no harm in getting an air source heat pump specialist around to your house to take a look. I think you’ll be impressed.” 

George Clarke is an architect, writer, lecturer and TV presenter, a founder of TV production company Amazing Productions, and creative director of George Clarke + Partners.