Heat pumps vs gas boilers - which is better and why?

The heat pumps vs gas boilers conversation is hot on everyone’s lips. Most people want to get their current boiler replaced, like for like, as affordably as possible. What adds confusion to the decision is longer term running costs. 

There could be a saving made by investing in a heat pump upgrade. The fact that this more modern, electric powered rather than gas powered, system is also more eco-friendly is another great bonus to changing heating source.

'As of 2022, the building regs are being updated to make it very difficult to make new homes compliant when installing a gas boiler,' says Doug Johnson from Mesh Energy. 'By the middle of the decade, new homes will have to emit 75% less carbon as part of the Future Homes Standard which supports a gas boiler ban in new homes from 2025. To reach net zero carbon emissions by 2050, we will need to change the way we heat our homes so heat pumps will quickly become mainstream.'

This guide aims to clarify all you need to know about the heat pumps vs gas boilers debate so you can decide which is the best option for you.

What is a heat pump?

There are two types: air source and ground source. We're only going to cover air source here as they're more common, easier to install and maintain, and are generally more efficient. Of the air source heat pumps these fall into two types: air to air and air to water heat pumps. As the names give away, one heats the air and the other heats the water directly.

Air source heat pumps uses electricity to run, a bit like an air conditioning unit works, only in reverse, to produce heat. The air to water unit takes heat from the outside air and heats the water in your central heating system directly. These are suited to underfloor heating or larger radiator-toting homes. The air to air heat pump also takes the heat from the outside air, and feed it directly into your home using fans. That means you will need a warm air circulation system to heat your home using one of these units.

For most people the air to water heat pump is the far easier and more affordable way to upgrade their current heating system. As such, these units are the ones which can be eligible for governmental monetary aid in the form of the Renewable Heat Incentive.

What is a gas boiler?

A gas boiler uses natural gas to generate heat. This takes gas, piped into your home directly, ignites it to create flame and uses that to heat water which runs through the boiler. The cold mains water coming in leaves hot to run around your home's radiators or to go to your taps for showers, baths, washing up and so on, directly in the case of a combi boiler.

A gas boiler, because it uses gas, can never be totally renewable in terms of energy. Gas provided by some energy companies is up to 20% renewable, meaning it will eventually run out as a finite resource, which is part of the reason why the heat pumps vs boilers debate occurs.

Heat pumps vs gas boilers: how they match up

For heat pumps vs gas boilers we first take a look at the pros and cons of each:

1. Initial cost to buy and install

The difference in cost between the two types of heating unit is pretty apparent up front. A classic gas boiler has been around for a long time meaning the technology has got cheaper and cheaper so now you can pick one up for less. The flip of that is that heat pumps are relatively new tech meaning they are still developing and the upfront cost can be significantly higher.

Across the UK, there are roughly 28 million homes and a gas boiler is used in 85% of these. The majority of the remaining 15% are oil boilers, because they're not connected to the gas network. Heat pumps, then, are still a relatively new technology. Part of that is due to the prohibitively costly upfront prices.

To replace a boiler like-for-like can mean an easy job with relatively few extra parts needed. To get a heat pump system you may need to do pipe reworking to fit the larger unit. You'll also need to have the space to fit one, with a pretty sizeable unit needing space to sit outside your property – similar to a large air conditioning unit. 

The other cost to factor in is insulation and radiators. You will need to have a well insulated home for a heat pump to work and use large radiators or underfloor heating. This is since heat pumps use air for heat meaning it's less intense than a gas boiler.

2. Efficiency

When it comes to efficient running costs with heat pumps vs gas boilers, long term, this is where money can be saved as the heat pump is far more efficient than a gas boiler. It also means you're able to use just electricity as opposed to relying on finite gas. Theoretically, the reality is that gas is cheaper than electricity but more on that below.

Gas boilers, thanks to condensers, are more efficient than ever but they still burn fuel to heat water. That means at their best you get an efficiency of 94%. Or in other words, for every pound spent six pence is wasted.

Heat pumps are a staggering 300-400% efficient. That means for a single kilowatt of electricity used you're going to get three to four times more energy.

3. Cost to run

Running costs, despite the efficiency figures, aren't as clear as you might expect when it comes to heat pumps vs gas boilers. Yes, you do get a lot more heat per the electricity used by going for a heat pump. However, electricity is more expensive than gas and oil. At time of publishing the price of electricity stands at 16.36 pence per kilowatt. Natural gas is nearly four times cheaper at 4.17 pence per kWh paid.

To give all those numbers a bit of context, the average UK home is using around 12,000 kWh each year to heat the place. For a 4kW heat pump that works out at £654.40 per year. The UK average gas bill, using the same 12,000 kWh, currently sits at around £572 per year.

While it looks like gas is cheaper and make you less likely to need energy bull help, you can actually save money thanks to the Renewable Heat Incentive, which pays homeowners for the heat their renewable system makes. This is due to be replaced by the Clean Heat Grant from April 2022 which helps with the upfront costs. You could also save money using solar power or wind to get free electricity to help heat your home. But of course you need that kit installed too.

Also, Mesh Energy's Doug Johnson makes the point: 'Electricity prices are about three times higher than gas prices but the way in which heat pumps efficiently use the electricity and take the majority of warmth from the air and ground is the key here. In a well-insulated home, due to these efficiencies the heating and hot water bill for the home is less than on gas. Electricity prices are also forecast to reduce in the future with the price of gas going up as it is subsidised less and fossil fuel pricing volatility continues.'

If you take into account lifespan, the heat pump looks even more appealing.

4. Lifespan

A heat pump has a lot less strain than a boiler and as such can last twice as long. While a boiler can last a decade, maybe 15 years if well maintained (which costs money), a heat pump can have a lifespan of up to 30 years when well-looked after (which is relatively easy).

There are plenty of boiler engineers that can carry out a Gas Safe Registered service on your gas boiler annually. As such the price of this can be lower. A newer heat pump will have fewer specialists to work on it, but there is less to actually mend in most cases meaning it could end up being more affordable – especially when you consider the longer term saving on not having to buy another. And in most cases you can carry out inspections yourself when it comes to heat pumps.

Essentially, for every one heat pump replacement you carry out, in that time you may have had to pay out for up to three gas boilers.

5. Maintenance

For both gas boilers and heat pumps, it is recommended that you have an inspection carried out annually. If you know what you're doing this can be done yourself, at no cost. But if you want a professional to come out, this will mean an expense. That said, you can sign-up to some services for longer term deals which cover multiple callouts, so you can pay up front and forget about it longer term.

With how to service heat pumps - of the air pump variety - there are filters that can be cleaned or replaced, coils and fans where the same can be done, fan blades to check and proper air flow to be checked. All pretty simple to do for most people, keeping costs down. Since most heat pumps come with up to a 10 year warranty, most costs are covered, should anything need replacing.

For gas boilers, due to the dangerous nature of the unit, it is recommended that any maintenance is carried out by a Gas Safe Registered professional. You'll also need to buy a carbon monoxide detector, available at Amazon, to be on the safe side. The average service of a combi gas boiler is £80 and should be done yearly.

Also: 'Heat pumps are inherently safer than gas boilers' says Jamie Luck of Baltic Consulting. 'Due to both the absence of a flammable fuel source and the lack of products of combustion including carbon monoxide.'

Heat pumps vs gas boilers: which is best for my home?

Ask yourself the following questions:

1. How much space do you have?

This could decide it for you right away. If you don't have enough space for a heat pump then a gas boiler could be your only option. A heat pump is installed outside the home on the ground, or affixed to the wall. This takes up an area that varies based on the power output of the unit you go for, larger homes needing more power. A 100 square metre house could be heated using a 5kW heat pump.

One of these units is about two metres long by 600 centimetres high by the same depth. That's not massive, but you will need to make sure there is plenty of space around the unit so it can draw in air. Also keep in mind anything near will have the cold output air being blown right at it.

A gas boiler is a lot smaller and can be fitted in your home inside a cupboard space. Ideal if you already have a gas boiler and are simply replacing it in the same space. But if you're going from a water tank boiler to a combi you may find this will be a new installation job – although you save the space of where the old water tank was.

While a heat pump is larger, it lives outside and so could save you on internal space currently taken up by your boiler.

2. Is your home well insulated?

If you don't have a well insulated home then you're already wasting money and energy by heating it where the heat can escape. In this case a gas boiler, which produces more intense heat quickly, you may be able to keep that home warm. But this is environmentally bad as well as being damaging to your bank balance.

A heat pump is less intense so it requires a well insulated home that will keep the heat in. So this is a good thing in terms of saving you and the environment. Government grants generally cover insulation upgrades to homes. This means you could have cavity wall insulation and your roof insulated without spending anything extra, potentially. 'Professionally insulating your home will significantly reduce your home’s heat loss,' says Keith Bastian, CEO of renewable home heating provider Fischer Future Heat. 'So if you can foot the initial outlay charge, you’ll save more on your heating bill in the long run.'

While a well insulated home is required for a heat pump, it should also be done for a gas boiler home to ensure you're not wasting energy.

The final verdict

If you have a home that has the space for a heat pump, which is also well insulated, then the longer term benefits of this modern home heating device are apparent. Factoring in the upfront costs and grants, you can save money on a heat pump. Especially if upgrading from an older boiler. It also means you're going to be helping the environment and are no longer reliant on gas, ideal if you have solar panels and want to be less grid reliant in general.

If you want to get the cheapest option up front and use minimal outdoor space, then a combi boiler could suit you well. This will produce powerful heating to keep even a less efficiently insulated home warm. It's also ideal if you want to heat your home from cold very quickly, as long as you don't mind the longer term maintenance costs and inherent risks with having gas in your home.