Greener Together
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Greener Together

The Modern-Day David Vs Goliath: Heat Pumps Vs Boilers.

With a growing public awareness and concern for the Climate Crisis, changing UK Building Regulations and Government investments into renewables- never have heat pumps been a more discussed topic.

The Challenge

The UK market is the biggest gas boiler market in Europe.

We install ~1.7million boilers per year.

85% of our housing stock uses boilers.

In the UK, heating our homes accounts for approximately 14% of our Greenhouse Gas (GHG) emissions.

However, currently less than a quarter of a million of the UK’s 29 million homes have heat pumps.

This means that heat pumps account for less than 2% of the market in the UK.

The Technology

In the heat pump vs gas boiler debate, you’re looking at two different technologies that are effectively delivering the same result: hot water and central heating.

That’s pretty much where the similarities end.

With the government promoting heat pumps (air-source and ground-source) as the successors to gas boilers as part of its Boiler Upgrade Scheme and scrapping of VAT, it’s the right time to be weighing up your options and how these two systems compare.

In this post, I break down the key differences in how these systems operate, alongside their efficiency, eco-friendliness and how much they cost to install and run.


To the homeowner, the two systems create the same result, but the difference in the way the two technologies work means that they need to have a different design setup when it comes to how the heat is delivered to the property.

  • A boiler will produce a lot of heat with a high temperature difference in a very short space of time. A boiler can thus work with radiators with a very high temperature.
  • A heat pump, on the other hand, produces heat more slowly and with a smaller temperature difference. Most heat pumps on the market work at a lower temperature and this can mean that the radiator (or emitter) would need to have a much larger surface area.

This also means that emitters such as underfloor heating (UFH), which run at a lower temperature than standard radiators, are an ideal emitter with heat pumps.

Ultimately, if you opt for a heat pump rather than a gas boiler, you will need to size the radiators and/or UFH pipe lengths very precisely.

It’s always worth checking the heat pump selection and system design with the heat pump manufacturer.

Building Regulations

Newly built homes are choosing heat pumps over boilers stating the banning of gas boilers by 2025 as part of the Future Homes Standards. Boiler manufacturers are also focusing on hydrogen ready boilers to keep their businesses going. There are several boiler manufacturers who also offer heat pumps to accommodate the shift in heating methods.

Regarding retrofitting existing homes, Chancellor Rishi Sunak has announced that VAT will be scrapped for insulation, solar panels and heat pumps in the Spring Statement 2022.

On top of this, replacing the Renewable Heat Incentive (RHI), the Boiler Upgrade Scheme (BUS) will launch in spring 2022 to aid the decarbonisation of buildings. It is set to provide £5,000 as an upfront capital grants to support the installation of heat pumps in homes (and some non-domestic properties).

At what point can I no longer install a boiler?

The provisional date of 2035 has been set out under Government targets that all new heating systems installed in UK homes will be either using low-carbon technologies (e.g. heat pumps) or supporting new technologies (hydrogen).

Given that the average lifespan of a heating system is about 15 years, if your heating system is nearing end of life, now might be an optimum time to consider making the most of the financial incentives that are available to switch across to renewables!

First things first

Regardless of heat source (whether you have a heat pump or a boiler) — you want to ensure that your property is well insulated.

Remember these guys?

Insulate Britain Protesters

Well — they had a point.

Whether or not you agree with their means, their message was spot on.

We need to insulate Britain.

We need to insulate our homes.

Irrespective of if you have a boiler or a heat pump (or any other form of heating system) — if your property isn’t very well insulated, then the heat you are paying for is just leaking out of your home.

You are throwing money out the window.

Fabric first everyone!

What type of heat pump is best for my home?

The type of property you live in (an apartment, small home, large home, new build or an old barn), the location of the property (city center or in the countryside), and any outside space restrictions you have will largely determine the type of heat pump that’s right for you.

There is no hard and fast rule, the best advice I can give would be to contact a design/ installation specialist who can assess your property (carry out a full heat loss calculation) and determine what’s the right solution for you as well as provide capital and operational cost guidelines based on your energy usage.

In this post I’ve provided a brief overview of the types of heat pumps that are available in the UK market, from Exhaust-Air Heat Pumps and Air-Source Heat Pumps, to Ground-Source/ Water-Source Heat Pumps.

Boilers are nearly 100% efficient — can a heat pump do any better?

A good boiler on the market is advertised as being ~90% efficient, when talking about heat pumps, the term CoP is used; Coefficient of Performance.

The CoP is the ratio of the amount of electricity used to the amount of heat produced.

As an example, if the heat pump uses 1kWh of electricity and produces 3 kWh of heat, then the CoP is 3 or can also be referred to as a 300% efficiency.

So yes, heat pumps can be extremely efficient.

With heat pumps however, it’s worth understanding that there are a lot of variables that go into calculating the efficiency, from the example above, we can produce 3kW of heat — but this may be at an ambient temperature of 5degC and a leaving water (space heating) flow temperature of 40degC — as the external temperature drops, to achieve the same leaving water temperature, the efficiency will likely also decrease.

This is why, if ever looking into ground or water-source heat pumps, you will likely see it stated that the efficiency that can be realised is much higher than that of an air-source heat pump, this is because the operating conditions can be fixed/ constant as opposed to that of an air-source system, where the ambient temperature fluctuates throughout the day and year.

What’s going to save me money on my bills?

As heat pumps run on electricity and a boiler burns gas, the running cost comparison needs to take into account the unit costs of this.

Currently, average electricity costs ~21p per kWh and gas is at ~4p per kWh across the country.

Based on pure financial cost alone, the heat pump would need a CoP of +5, or in other words, have an efficiency of +500%, to even be comparable.

As the cost of electricity and the cost of gas change, so will this calculation. You also need to be sure that the system will indeed achieve the indicated efficiencies.

One thing is for sure though. The cost of energy will continue to rise and the gap between the cost of electricity and the cost of gas is sure to close.

At the moment the switch from gas to a heat pump may not make financial sense, but as the energy cost gap closes, the numbers will certainly become more favourable for heat pumps.

What’s the answer?

As energy prices continue to rise and nations push for energy independence, as a homeowner a key focus should be in preparing your home for the future — ensuring resilience through reducing your energy demand (insulation, insulation, insulation!) and increasing your energy efficiency, whilst simultaneously moving away from a reliance on fossil fuels (the supply of which is finite).



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