Plumbing Tips

Heat Pump vs Gas Boiler: Everything You Need to Know

When it comes to heat pump vs gas boiler, which is better? How do they work? What exactly is a heat pump anyway?

If you want to compare and contrast a heat pump with a traditional boiler – either for upgrade purposes or because you’re concerned about a possible “gas boiler ban” in the future – you’ll find everything you need to know here.

This article is for you if:

  • You want to know more about heat pumps and how much switching to one costs
  • You’re interested in how heat pumps work and their pros and cons
  • You need to know if heat pumps are suitable for the UK climate or your home

What is a heat pump?

There are two sorts of heat pumps – air source heat pumps and ground source heat pumps. These are the differences between the two:

Air source heat pumps

An air source heat pump is a renewable heating system that takes heat from the air outside your home to heat the inside and your hot water.

This isn’t the same as using wind energy. The pump extracts heat from the air (even very cold air that you might think is too cold for this to work!).

Air source heat pumps work by drawing in air from outside your home. This air is passed over a refrigerant fluid in an exchanger coil. The fluid boils and evaporates, becoming vapour. This vapour is then compressed to produce heat.

There are two types of air source heat pumps, which have different advantages depending on your property type:

  • Air-to-air heat pumps – use fans to circulate around your home.
  • Air-to-water heat pumps – heat up water for heating your home.

Ground source heat pumps

As you might expect, ground source heat pumps utilise underground heat to heat the air or water in your home. No matter what time of year it is, the temperature underground is generally around 10-15°C, so even when it’s freezing outside, your heat pump will work.

The heat is extracted from the ground using a buried pipe-like device known as a “ground loop”. This is at least two metres down and sometimes in a borehole as much as 150 metres deep.

This ground loop pipe is full of liquid, a mix of water and antifreeze. The liquid absorbs the heat underground, which is then extracted by the heat pump through compression of the gases the refrigerant liquid gives off.

The heat this process creates can then be passed around your home or used to heat your water. A ground source heat pump is a highly efficient renewable system.

What is a gas boiler?

Most people are passingly familiar with the kind of traditional gas boiler you find in most homes in the UK.

These boilers accept gas that comes directly into your home through pipes. That gas is used to create heat (a flame) that heats the water in the boiler. This is then used to heat the house – usually via radiators – and water.

Some energy companies use gas that is to some small degree renewable. Gas is also sometimes touted as a “transition fuel” between fossil fuels and newer, cleaner, greener options.

Yet, when it comes down to it, you’re still burning a largely non-renewable energy source that is subject to price variations.

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Gas boilers vs heat pumps: what are the key differences?

When it comes down to a straight-up heat pump vs gas boiler fight, which comes out ahead?

Different people are often looking for different qualities in their home heating system, so let’s break down the comparative pros and cons of heat pump and boiler in a few different areas:

Efficiency

Efficiency is the word that’s used to describe how much of the energy supplied is turned into heat by your heat pump or boiler.

The most advanced gas, LPG, oil, or biomass boilers can reach 90% efficiency. More standard boilers are somewhere around 50-75% efficient.

Heat pumps can be anywhere from 300% to 400% efficient. They’re absorbing energy from the air or ground to make heat happen, which is a far better system. It’s also not subject to variations in gas prices or stock running out, which it eventually will.

Running costs

At the time of writing, heat pumps are still cheaper to run than a gas boiler. But it’s not quite as big a difference as you might expect.

Electricity, as it stands, costs roughly four times more than gas. However, the incredible efficiency that a heat pump offers means it remains more cost-effective despite this.

However, this is expected to change in the near future, with the volatile electricity market becoming less expensive, making heat pumps a much clearer winner. This will be even more noticeable if the UK finally gets its act together on green energy and starts having its own secure, more cost-effective supply of renewables.

There is also the fact that the UK does subsidise homeowners who heat their home and water using renewables. This used to be called the Renewable Heat Incentive but is or soon will be replaced by the Clean Heat Grant (slated to begin April 2022). Either way, it’s possible to get money back when using green energy.

Cost to buy

The one area where a traditional gas boiler wins out over a heat pump is the initial upfront cost.

Most of the homes in the UK (around 85%) have gas boilers. Most of the others have oil boilers because they aren’t connected to the gas network.

Gas boiler technology is getting pretty long in the tooth. But decades of development and improvements mean the technology is now comparatively cheap (even if it doesn’t always feel that way).

Installing an air source heat pump or ground source heat pump is currently much more expensive though, partly because the technology is new. Most homes also require some adaptations – in the form of alterations to pipework, a unit sited outside your property, improved insulation, and often larger radiators or underfloor heating – which can add to the cost.

Lifespan

Your common or garden boiler can last – at best – fifteen years if you keep it well maintained (maintenance, of course, is another factor to consider in the debate).

The lifespan of even this relatively early generation of heat pumps is twice or three times that. This means the cost of one heat pump should really be compared to that of two or three boilers.

Maintaining a heat pump tends to require far less attention than a gas boiler too. Less intensive demands are placed on the system, which tends to mean less stress and fewer things that will go wrong.

Currently, there are fewer experts who can perform the equivalent of a Gas Safe Registered maintenance service on your heat pump. But this is less of a concern as you’ll need one less – it’s also likely to change in the future.

Maintenance

Heat pumps don’t have flammable materials being piped into them from outside your home or produce dangerous by-products like carbon monoxide.

The upside of this is that, while you should have an annual maintenance inspection carried out on your heat pump just like a boiler, it might be possible to take care of it yourself. Most repair work will be things like replacing a filter or checking proper airflow or fan blade condition – pretty easy stuff.

You should also be covered by at least a decade-long warranty if you get a new pump fitted.

How to know if a heat pump is right for your home

Considered side by side – a straight-up battle between ground or air source heat pump vs gas boiler – there is really only one clear winner. The heat pump. There’s a reason why they seem to be on everyone’s lips at the moment.

For most people though, it’s not a choice that can be made in a vacuum. Your house is as it is. This means there are certain other considerations that need to be borne in mind when considering whether a heat pump is right for your home specifically:

Space

Most people are aware of roughly how much space a boiler takes up. Most homes in the UK are designed with the space a boiler needs in mind.

But air source heat pumps come in split or monobloc units that take up quite a bit more room. Luckily for some homes, this is space that needs to be outside your property. For others, this is less good news. It means these pumps aren’t suitable for blocks of flats, for instance.

The same is even more true for ground source heat pumps. These require that a borehole be dug and can mean significant change and disruption.

Insulation

Good insulation is important whether you are heating your home with a boiler or a heat pump. But heat pumps are much more reliant on the quality of insulation you have. They may also require you to get bigger radiators fitted.

Almost every home in the UK could stand to have better insulation (a recent professional survey found that 25 million+ UK properties were in need of it – that’s effectively every single home). If you’re considering how to improve your heating situation at home, better insulation can be a great place to start either way.

At what temperature can a heat pump work efficiently?

One final consideration that many people worry about is the temperature that a heat pump can work efficiently at. The message here is, essentially, there’s no need to.

The countries that are leading the way in Europe in fitting heat pumps (far outstripping the UK) are those that are even colder. In fact, the current leader in the number of heat pump installations per day is Norway – not exactly renowned for its balmy year-round temperatures!

It’s hard to picture it. But both air and ground source heat pumps are designed to work in temperatures below zero.

Takeaways

  • There are two types of heat pumps, air source and ground source, and they work quite differently.
  • Both types of heat pump work even in sub-zero conditions
  • Compared to a gas boiler, heat pumps are superior in almost every way
  • The one exception is upfront installation cost, where heat pumps currently tend to be much more expensive
  • Heat pumps also require your home to be suitable in terms of space and insulation if you’re going to get good value from them

Did that answer all your questions comparing heat pumps vs gas boilers?

Comment below and get a fast answer from an expert in the field!

Image source: Nsit/Studio Harmony/shutterctock.com

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