Air Source Heat Pumps vs Gas Boilers.

Article by: Sam Dewey

Introduction

Air source heat pumps are the most popular type of heat pump on the market nowadays used specifically for environmentally friendly space heating and hot water for domestic and commercial properties. There have been various incentives by governments to help increase the uptake of heat pumps in both new and old homes.

On the other hand, gas boilers are hands down the most common heating appliance that can be found already installed in millions of households across the UK. There is an extensive gas network to provide gas to each of these homes but will have quite a few significant issues approaching it in the near future.

Both modern air source heat pumps and gas boilers can be very efficient appliances in terms of using their respective fuels to generate heat, but even though they can both provide heating and hot water for a property, there are several differences between them.

To be able to make an informed choice, you need to understand each option thoroughly. Whilst a direct gas boiler replacement is often the cheaper option, installing an air source heat pump can help to reduce your carbon emissions, as well as cut your energy bills, massively.

In this article, we’ll weigh up both options, comparing the two rigorously and hopefully helping you to make the right decision for your property.

Air Source Heat Pumps vs Gas Boilers: The Key Differences.

There are a number of key differences between air source heat pumps (ASHPs) and gas boilers.

Both setups require a certain fuel for generating heat and they use different methods, materials, placements for doing so. They also have different purchase, installation, running and maintenance costs which we will soon discover. Here are the main differences between air source heat pumps and gas boilers:

Pre-Installation Work: On-site Survey and Preparation.

The first step after you have contacted Heat From Air, will consist of an onsite inspection to check the suitability of your property in order to install the chosen heat pump.

Here at Heat From Air, we are also trained to safely remove any existing system such as a gas or oil boiler. Heat loss calculations will be made to determine the size of the heat pump that needs to be installed. The inspection is an important step in planning the installation correctly!

Once this is done, we will prepare and design a report with sketches of the property for efficiency installation of the system. Depending on the size of your property, heating needs and how well your home is insulated, a recommendation will be made to an appropriate type and size of an air source heat pump. After you are happy and we have everything we need to progress safely to the next step, the installation process will begin.

Air source heat pumps use electricity instead of gas.

Air source heat pumps are electrical appliances and only use electricity as the form of power. This means that an ASHP does not need to be supplied with any fuel such as oil or gas to work and simply need to be connected to the mains house electrical supply.

There are no direct emissions from this process and heat pumps can generate multiple times more heat energy than the electrical energy they consume. Heating is however provided more slowly and at lower temperatures, and a hot water tank will be required if using for domestic hot water.

Gas boilers of course use gas as the source of fuel and utilise a combustion process to generate heat. Some energy is wasted in this process and generates some emissions. Heating can be provided very quickly, and a hot water tank may not be required as domestic hot water can be provided on demand.

Both appliances use water-based central heating systems to heat a home, although the alternative type of heat pump system, air to air, can provide space heating rather than central heating.

Air source heat pumps need to sit outside, while gas boilers are installed inside.

To generate the heat for the property, air source heat pumps move heat from outdoors to indoors and so the main external heat pump of the system needs to be located outdoors.

External heat pump units are installed in an open but secluded location so that they can extract heat from the air. This, among other factors, allows heat pumps to work as efficiently as possible. This would usually be down the side of a house if there is appropriate space. However, it’s important to keep in mind that hot water tanks for hot water storage will be installed inside the property.

A typical gas boiler will sit inside a property, whether that’s up against an external or internal wall, or stored away in a cupboard.

As air source heat pumps don’t generate heat through combustion, meaning they don’t need an oxygen supply, although they do need air in which to extract heat from. Oxygen, however, plays a crucial role in the burning process of all gas boilers and so typically must have a dedicated fresh air supply.

Air source heat pumps and gas boilers both have a pretty similar installation process as the heat pump controls and pipework are similar to traditional boilers. Click the link if you would like to find out more about a typical air source heat pump installation process in the UK.

Air Source Heat Pumps vs Gas Boilers: The Costs.

To get an accurate picture of the two systems, we need to delve into the initial upfront cost. and the running costs of both systems.

Air source heat pumps can have a higher upfront cost.

When it comes to upfront cost, gas boilers are typically cheaper than heat pumps. Although the process of installation is similar, the raw materials are less costly. Overtime, this will change and ASHPs will get cheaper especially when gas boilers start to get properly phased out in the coming years.

Furthermore, with gas central heating systems so common in households, upgrading to a more modern and efficient boiler can be much less expensive than installing a new ASHP unit and upgrading the indoor heating system alongside it but the environmental benefits will still be significantly lower.

There are however many financial and other incentives to upgrade to an air source heat pump from a boiler such as the UK’s Boiler Upgrade Scheme, which can help reduce initial costs up to £5000.

It’s important to also consider the lifespan of the boiler or heat pump, as well as the ongoing costs such as running costs and maintenance.

Both systems have similar running costs, for now..

While air source heat pump installations may have a higher initial cost, it’s essential that you weigh up the running costs of whichever heating method you choose. After all, you need to know what you’ll be paying for your energy in the long term.

Gas can be, on average, cheaper than electricity in terms of energy costs from your provider. However, as air source heat pumps can be much more efficient than gas boilers (which we discuss more about below), the running costs for either a gas boiler or an ASHP can be very similar.

You can further reduce the running costs of a heat pump by installing solar panels on your property. This means that your heat pump will be largely powered by renewable energy during daylight hours, helping to keep your running costs to a minimum. With gas prices peaking to an all time high, ASHPs are looking the much more viable option moving forward.

Average cost of replacing an existing gas boiler with an air source heat pump..

Deciding whether to replace an old gas boiler with an air source heat pump depends on a number of factors. If you own an old draughty home which costs a lot to heat then installing decent levels of insulation and cutting down on draughts would first be essential.

As we’ve previously mentioned, air source heat pumps are likely to be more expensive to initially install but there are other factors to take into consideration. If the gas boiler is quite old then there may be other parts of the system that also need to be upgraded (see table below) as gas safety regulations change over the years.

Other potential upgrades required	Approx. Cost
New condensate pipework (if old boiler is not a condensing boiler)	£150 – £250
New gas flue	£200 – £500
Replace gas supply pipe (if supply pressure insufficient)	£150 – £300

A site survey would need to be done by a Gas Safe Registered Installer, to identify if any or all of this work needed doing. Luckily, our team can sort this for you!

Upgrading of any electrical wiring, the hot water cylinder and the control system will probably need to be done with either a replacement gas boiler or a heat pump. A key question to answer is whether the radiators are of sufficient size to heat the room using the lower water temperature provided by the heat pump. If not then these will need to be upgraded in size. Pipework with an increased diameter will also be needed.

It may be smarter to spend the money on upgrading the insulation in your home, reducing the energy required to heat each room; in this case the old radiators and pipework may then be suitably sized to heat the better insulated room with a heat pump.

Boiler Upgrade scheme.

In October 2021 the UK government announced a Boiler Upgrade Scheme to help householders and small commercial owners changing from a gas boiler to a heat pump (air source or ground source). The £450 million scheme will run until April 2025 and offers a payment of £5,000 per property towards installing a new heat pump. To find out all about this scheme, read our article here!

Air Source Heat Pumps vs Gas Boilers: Maintenance.

System maintenance has and always will be critical for keeping your heating appliances in tip top condition. We recommend that you arrange for maintenance checks annually for air source heat pumps, but it is not a requirement but please remember that Maintenance will extend the lifespan and preserve efficiency of the system. Get in touch with the Heat From Air team to find the best maintenance plan for you.

Boilers however need maintenance checks annually at the very least. An effective maintenance plan can and will protect you against carbon monoxide poisoning risks. But also, old gas boilers love to play up when they haven’t been used in a while, and at the worst times.. Don’t be left in the cold this winter!

Air Source Heat Pumps vs Gas Boilers: Lifespan.

There’s no point investing in a heating method for your property if it’s unlikely to last no more than a couple of years. For this reason, it’s important to understand the expected life span of your boiler or heat pump before making the decision to invest.

A typical gas boiler will last for 10-15 years with regular maintenance before needing to be replaced. In contrast, heat pumps have an average lifespan of 20 years, with some heat pumps lasting up to 25 years before requiring replacement.

Air Source Heat Pumps vs Gas Boilers: Efficiency.

Efficiency in heating systems equates to the volume of the energy they supply that is converted into heat energy. Energy efficiency ratings and numbers to look out for can include:

Coefficient of Performance (COP)
Seasonal Coefficient of Performance (SCOP)
Energy Efficiency Ratio (EER)
Seasonal Energy Efficiency Ratio (SEER)

Discover the meaning of these energy efficiency ratings here!

Air source heat pumps are more efficient.

Traditional boilers have a 50 to 75% efficiency rate, meaning around a third of the supplied energy to the boiler is wasted. Even biomass boilers and modern oil, LPG and gas boilers have an efficiency at around the 90% mark.

Air source heat pumps topple this by a country mile, reaching up to an average 350%, with a coefficiency of performance (COP) measuring 3.5. In ideal conditions however, an air source heat pump can be 400% efficient, which is truly mind blowing.

Now, it’s not always going to be the ideal conditions for a heat pump to work in and outdoor air temperature can significantly affect the efficiency of an ASHP.

At lower outdoor air temperatures there is greater temperature difference between the outdoor and indoor air temperatures, and so more power input is required to generate the same level of heat, therefore reducing the performance coefficient/ratio.

The air source pump will work out cheaper long-term and you can claim much of the initial cost back through grants, but the gas boiler is cheaper up front. What’s best for you depends on your priorities, whether long-term or short-term.

Air Source Heat Pumps vs Gas Boilers: Features.

It’s important to note that gas boilers can only used for heating and hot water and not for cooling in the warmer months. Whereas most types of air source heat pump systems can be used to efficiently cool a home as well as heat it.

Air to air heat pump systems, which provide space heating through heated air, can also be very effective as a cooling system by reversing the heating process, similar to how air conditioning systems operate, and they can do this at a very efficient and effective level.

Now, a cooling system isn’t such a necessity in the UK as we don’t often have to deal with extreme weather conditions, but it is quite a nice feature to have at hand just in case. However, the UK’s leading meteorologists have warned that British summers are likely to regularly see temperatures above 40 degrees Celsius (as we saw in 2022) due to global warming issues across the planet.

Air Source Heat Pumps vs Gas Boilers: Environmental Impact.

The environment is an ongoing concern in the modern world, so there’s no wonder that many people are looking for ways to reduce their carbon footprint and installing an air source heat pump is one of the best ways to achieve this.

As we have mentioned in the efficiency section of this article, there is absolutely no competition close to the modern-day air source heat pump in terms of energy consumption. Although modern LPG, oil and gas boilers offer around 90% efficiency, as heat pumps do not use any fossil fuels whatsoever, they are currently the best option on the market.

The fact that they offer such high efficiency means that even if they use electricity derived from a coal-fired power generator, the volume of carbon emissions they’d generate would still be very minimal compared to a gas boiler.

Also opting to have heat pumps powered by green electricity such as wind or solar, can reduce carbon emissions generated to zero or close enough. Paired with mechanical heat recovery ventilation (MVHR) in commercial properties, creates an energy efficient all-in-one solution to heating and ventilation in which incredible efficiency figures can be achieved.

The MVHR system is able to recover over 90% of the heat from the outgoing stale air before feeding it back into the building as warm, fresh, filtered air. Especially during winter where the ASHP may lack in terms of efficiency, MVHR systems can increase their efficiency by up to 10%, taking that extra strain off of the heat pump.

Air Source Heat Pumps vs Gas Boilers: Space Requirements.

Traditional gas boilers don’t take up too much space. This is particularly the case with combi boilers which do not require a hot water cylinder. This makes gas boilers well-suited to small properties where space might be limited.

In contrast, air source heat pumps require a slightly larger amount of space. This is due to heat pumps requiring both outdoor space, as well as indoor for the indoor unit and a hot water cylinder. As air source heat pumps deliver heat more slowly and at lower temperatures, they can’t provide domestic hot water on demand and so must be paired with a suitable hot water cylinder.

The use of a hot water tank allows domestic hot water temperatures to be built up over time so that they’re at temperatures users would deem as ‘hot’. A hot water tank suitable for use with an ASHP system may also have one or more built-in electric immersion heaters to help keep temperatures topped up when demand for hot water is high.

A traditional gas boiler may also be used alongside a hot water tank, but the use of a combi-boiler allows hot water to be provided on demand without the need for a storage tank.

So, if you’re considering having a heat pump installed on your property, you’ll need to ensure that you have enough space available for the equipment.

Air Source Heat Pumps vs Gas Boilers: Ease Of Use.

The user experience of both air source heat pumps and gas boilers will depend on the model you choose as modern systems are fully automatic. You will find, as is the case with the majority of modern appliances, there are various extras to consider that improve the control, comfort and how easy they are to operate.

Some of these are worth considering, including programmable thermostats, timers, and application-controlled systems (mobile apps). Aside from this though, you’re going to get similar automation options with either heating system.

Air Source Heat Pumps vs Gas Boilers: Future Proof.

With environmental issues being at the forefront, we are all being encouraged to opt for greener energy sources. With Governments promising to reach zero carbon emissions by 2050, the future looks uncertain for boilers, especially with gas boilers being banned from installation within new builds from 2025 onwards.

All gas boilers are supposed to be scrapped in the future, however, in the UK our gas network is extensive. The National Grid suggests that about 80% of British homes have a gas boiler. Transitioning all of these homes could prove difficult, but the challenge is set to improve the environment so boilers could and most definitely should be on their way out in the future.

Air Source Heat Pumps vs Gas Boilers: The Verdict.

For many years, gas boilers have been seen as the traditional way to heat your home and your hot water. However, in recent years, heat pumps have soared in popularity, thanks to their eco-friendly design, as well as their ability to reduce energy bills. Although heat pumps are becoming more popular, the UK is still lagging behind European countries such as Norway, where over 60% of properties is heated by some sort of heat pump system.

When it comes to air source heat pumps vs gas boilers, there are many factors that you’ll need to consider ensuring that you choose the right option for your property. These include cost, installation time, environmental impact, and the space that you have available. It’s important to make the right decision, as your heat pump or gas boiler will be heating your property for many years to come.

Unfortunately, if you were looking for one that stands out from the crowd as being the best, even after considering all the points above, it’s a very difficult decision. They both do a supreme job at heating properties up but one of them operates at a far superior efficiency level.

A heat pump is our recommendation if you are not connected to the mains gas supply, are constructing a sustainable property, want generally cheaper bills with less maintenance, or just want to have an eco-friendlier life. Afterall, net zero is the future so why not let your green future start here with Heat From Air.