Boiler Or A Heat Pump?

In Scotland, the majority of gas boilers are set to be phased out by the year 2035. Gas boilers use a lot of energy, and create emissions and a lot of wastewater. For these reasons, the government is encouraging homeowners to switch to more environmentally friendly alternatives.

Many are switching to boilers that don’t burn fossil fuels, like electric boilers. Others are totally transforming their home heating system by investing in a heat pump. These systems transport natural heat from outdoors and bring it indoors, heating your home just as well as a gas boiler would.

Are you trying to decide whether switching from a gas boiler to a heat pump is a worthwhile investment? In this guide, we’ll weigh the pros and cons of each and help you reach a conclusion.


What's Covered

Heat Pumps vs Gas Boilers Comparison

As it stands, the majority of homes in Scotland are heated with a gas boiler. However, the more eco-conscious amongst us have already made the switch to heat pumps. But it doesn’t only take an eco-friendly initiative to make the switch to heat pumps, it also takes a significant amount of up-front investment.

As we’ll explore later, heat pumps are essentially a new type of heating system that requires time and effort to install. For many, this hassle isn’t worth it, so they opt to have a new gas boiler installed instead.

However, given the fast-approaching deadline for the 2035 initiative, the Scottish Government is already making moves to completely phase out gas and oil boiler models. From April 1st 2024, it will be illegal to install a newly built home with an oil or gas boiler. So, the biggest comparison that can be made between gas boilers and heat pumps is that the latter will become more prominent in future.

However, there are lots of other differences between the two heating systems, as we’ll explore throughout this article.

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What Actually is a Heat Pump?

A heat pump is an energy-efficient heating system that draws in air from outside your home and transfers it inside. As the name implies, these devices effectively pump heat in from the outside. It does this by extracting thermal energy from the outside and passing it through a coolant, which turns the low-grade thermal energy into hot energy.

Here’s a breakdown of how heat pumps work:

  1. Heat is sourced from outside.
  2. The heat causes the refrigerant liquid in the heat pump to turn into a gas.
  3. The gas goes through a compressor to increase its temperature.
  4. The heated gas passes over a heat exchange surface.
  5. The heat can then be moved to your central heating or hot water system.

This hot energy can then be sent to your radiators to heat up the different rooms of your home. It can also be used to heat up water, so you can have a hot shower or bath.

The low-grade thermal energy can be gathered from the ground, air, or both. Water-source heat pumps are also available. For each of these options, there is a different type of heat pump:

  • Ground source heat pump: Ground source heat pumps utilise the stable temperatures of the ground in order to heat your home. Sometimes referred to as geothermal heat pumps, these heating devices conduct heat via a loop of pipes buried several feet below the surface of your garden. These pipes are filled with the heat transfer fluid.
  • Air source heat pump: Air source heat pumps work similarly to a refrigerator or an air conditioner – only, in reverse. An air source heat pump consists of an outdoor unit fitted to the outside wall of your house. This unit contains a fan, refrigerant, and a compressor. The fan pulls in the air from outside, compresses it, and then sends it to your room indoors, which provides heat.
  • Hybrid heat pump: A hybrid heat pump works alongside another heat source, such as a fossil fuel-powered boiler. This system can function no matter the outside conditions. Depending on the conditions, the pump will automatically switch between air-source heat and boiler-produced heat. While this isn’t 100% environmentally sound, it provides some reduction in fossil fuel usage.
  • Water source heat pump: Although less common than the likes of an air source heat pump, it’s possible to get a water source heat pump. This type of heat pump extracts heat from a water source such as a nearby pond, lake, river, or well. The heat is extracted using a heat exchanger, which then goes through a refrigerant cycle before being transferred to the indoor air.

In Scotland, you’re not always going to get warm outside air – more often than not, it’s freezing. For this reason, many opt for hybrid heat pumps, as they can still provide warmth during the coldest of winters.

Can heat pumps cool a room?

Air-to-air heat pumps can also work in reverse. Instead of pulling in air from the outside, you can reverse your heat pump during the summer to extract warm air. When in cooling mode, air pumps absorb heat, evaporate this heat into a gas, and then pump it outside. This ensures that the inside of your home can stay cool during the heat of summer.

boiler v heat pump

Heat Pump vs Gas Boiler: Which is the Quickest to Install?

Gas boilers definitely win in terms of installation speed. No matter where in Scotland you are located, there will be a Gas Safe Engineer in the vicinity ready to install your gas boiler in a matter of hours. This is especially true if you’ve previously had a gas boiler and you’re merely getting a new one fitted.

Even if you’re getting your first-ever gas boiler installed, installation time is nowhere near as long as a heat pump. If it’s your first-ever gas boiler, you can estimate an installation time of somewhere between six hours and four days.

Heat pumps, on the other hand, are a relatively new system, meaning that booking a heat pump engineer is far trickier than a gas boiler engineer.

Plus, heat pumps require far more installation steps than gas boilers do.

For example, during the initial site assessment, a few days are needed to determine what type of heat pump your home requires, as well as how it will be positioned. If it is decided that you require a ground source heat pump, infrastructure preparation and groundwork will add a few extra days to the installation time.

The installation itself can take a few days to a week. During this time, the engineer has to fit the indoor and outdoor units. They also need to connect the refrigerant lines with the power supply and controls.

Lastly, the air pump needs to be tested by the engineer to ensure that it’s in working order and that it’s operating safely.

Overall, heat pumps can take as long as six weeks to install.

heat pump outside

Heat Pump vs Gas Boiler: Up Front Costs Comparison

Heat pumps are much more expensive than gas boilers in terms of upfront cost.

For a boiler itself, you can pay as little as £600 for a budget combi boiler. More premium boilers will cost you a few thousand pounds. In total, the cost you’d have to pay for the boiler itself plus installation costs is somewhere between £1,500 and £3,500.

The cost of a heat pump is much more expensive than this. This is due to the scarcity of heat pump styles and the expensive materials used to build the heat pump, in addition to the cost of paying for the six-week installation process. Every home is different, so each heat pump installation needs to be carried out bespokely. This drives up the price you have to pay for the pump.

Typically, the price you’ll have to pay to cover the purchase and installation costs of an air source heat pump is in the region of £8,000 and £15,000.

Ground source heat pumps cost more and typically fall between £18,000 and £25,000. This is mainly due to the trenches that need to be dug to successfully install the pump.

However, to make the cost of installing a heat pump more affordable, governments have introduced discount initiatives. These have been put in place to encourage more households to make the switch from fossil fuels to environmentally sound heating options. We’ll cover what government grants are available to Scottish households later in the article.

Heat Pump vs Gas Boiler: Running Costs Comparison

In theory, heat pumps should be cheaper to run than gas boilers. They’re much more energy efficient and require less energy to operate in the first place. However, heat pumps rely on electricity, while gas boilers rely, obviously, on gas.

In the UK, electricity is more expensive than gas. Between July and September 2023, the average household paid 27.67p per kWh for electricity. During this same period, the average household only paid 6.77p per kWh for gas. For this reason, households who recently switched to air-source heat pumps may have paid more for energy than households who had stuck to gas boilers.

However, this price difference will not always be the case. If the price of electricity goes down in the future, heat pumps could be seen as the more viable option once again.

The running costs of your heat pump also come down to how well-insulated your home is. If your house is well-insulated, your heat pump won’t need to produce as much heat. This means that it also won’t need to use as much electricity.

Heat Pump vs Gas Boiler: Which is More Energy Efficient?

Heat pumps are more energy efficient than boilers. All that heat pumps require to operate is a small amount of electricity – the rest is done purely by natural resources. For every single kWh of energy that a heat pump produces, 75% comes from the air or the ground, while the remaining 25% comes from electricity.

Heat pumps don’t rely on fossil fuels nearly as much as gas boilers do. They also don’t produce as many CO2 emissions and convert as much energy as possible from their energy source.

Gas boiler efficiency is measured by Annual Fuel Utilisation Efficiency (AFUE), which determines how much of the gas used by the boiler can be converted into heat energy. Based on AFUE, gas boilers convert 90% of the energy they use. This means that 10% is always wasted. This would mean that for every £1 you spent on gas, at least 10p would be wasted.

This is assuming that your gas boiler is efficient and you have good insulation. You could be losing significantly more in wasted gas if this weren’t the case.

Heat pumps, on the other hand, produce more energy than they use. For every 1kWh of electricity they use, a heat pump produces 3-4 times as much heat.

Generally, air-source heat pumps have an energy efficiency rating of 300%. Ground-source heat pumps, on the other hand, have an energy efficiency rating of 400%. For this reason, heat pumps are definitely the most energy-efficient of the two heating system types.

Heat Pump vs Gas Boiler: Heat Output Performance Comparison

Gas boilers have a better heat output performance. This is mainly due to its higher flow temperature and the speed at which it can deliver this temperature to wherever it needs to be around your home. Gas boilers have a high flow temperature of around 70 °C for both radiator systems and hot water.

Heat pumps, on the other hand, have flow temperatures of 55 °C for hot water and between 35 °C – 45 °C for radiators. This lower temperature means that heat pumps cannot provide heat as quickly as gas boilers can. However, heat pumps can still provide a high level of heat once they’ve been left on for a period of time.

So, while gas boilers may have a higher performance level than low-carbon heating alternatives, at least a high heat level is still attainable with an energy-efficient heat pump.

heat pump enviro homes

Heat Pump vs Gas Boiler: Which Wins the Carbon Footprint Battle?

Heat pumps definitely win the carbon footprint battle over gas boilers. They rely on the ground, water, and air, each of which is a renewable energy source. While heat pumps still produce carbon emissions, they produce at least 30% less than gas boilers. Unlike gas boilers, heat pumps don’t necessarily need to rely on any fossil fuels.

If you’re able to pair a heat pump with a renewable electricity supplier, like solar power, you can make your heat generation 100% carbon neutral.

Natural gas boilers emit roughly 215 grams of CO2 for every kWh of heat produced. Not only do gas boilers use up fossil fuels, but they also produce significantly more greenhouse gasses than heat pumps. For these reasons, they leave a far bigger carbon footprint than heat pumps.


Heat Pump vs Gas Boiler: Will Heat Pumps or Hydrogen Boilers Replace Gas?

Both heat pumps and hydrogen boilers will replace gas boilers, as will other low-carbon heating systems. As gas boilers continue to get phased out across the UK, both heat pumps and hydrogen boilers will continue to be promoted as the main low-carbon heating alternatives.

The only reason that more people aren’t getting heat pumps at the moment is because of the high asking price for the devices. And, potentially, because gas boilers are currently cheaper to run than heat pumps.

While they’re not being adopted widely at the moment, it is hoped that the price of heat pumps will go down in the coming years. As Scotland plans to stop new houses being built with gas boilers (or old houses that haven’t got a heat pump installed being sold) it makes sense that the price of these low-carbon heating options will gradually decrease over time.

Are You Eligible for a Free Boiler or Heat Pump?

There are schemes currently running that can help Scottish homeowners get either a free boiler or a discounted heat pump. These schemes are:

The ECO4 Scheme

Some homeowners in Scotland can get a free energy-efficient condensing boiler through the ECO4 scheme. This scheme is targeted at low-income households who are currently using boilers with a low-efficiency rating. Not only will you receive the boiler for free, but you’ll also get it installed free of charge, too.

Once installed, you’ll save money on energy bills through the use of your more energy-efficient boiler. This new boiler will feature a timer and a room thermostat. Thermostatic radiator valves (TRVs) will also be fitted onto all of your radiators.

To qualify for this scheme, you must own your property and your boiler must be either broken or inefficient. You also are required to receive a benefit payment, such as House Benefits, Income Support Benefits, or Pension Credits.

The ECO4 Scheme can also be used to acquire your own heat pump. If you’ve never had a heating system before, you can apply for a grant via the ECO4 scheme, which is specially designed to help you purchase an air pump. This grant is titled the ‘First Time Central Heating Grants Scheme‘.

The ECO 4 Scheme is scheduled to run until the 31st of March 2026.

The Home Energy Scotland Grant and Loan

This scheme is designed to make the purchasing of heat pumps more affordable for homes across Scotland. Successful applicants can receive a grant of up to £7,500 that can be used towards the purchasing and installation of a heat pump.

In addition to this, you can also borrow £2,500 as an interest-free loan. This loan is given to go towards your heat pump, and can choose how long you take to pay back the loan (between 5 and 12 years).

Households that qualify for the rural uplift can receive a grant of up to £9,000 from this scheme. To qualify for the rural uplift, your property needs to be located in a remote or rural location in Scotland. If you contact Home Energy Scotland and tell them your address, they’ll be able to inform you of whether or not your property qualifies for the rural uplift.

If you do qualify, you could also receive £1,000 towards your heat pump purchase as an interest-free loan.

Final Thoughts

When it comes to heat pump vs gas boiler heating systems, the low-carbon heating system is the winner. While it can be costly to install and (currently) maintain, both ground and air-source heat pumps are the most energy-efficient option when it comes to home heat. Plus, with gas boilers slowly being phased out, now is as good a time as ever to switch to a heat pump.

Installing a heat pump can be made a lot more affordable by applying for the ECO4 scheme. This will allow you to install a heat pump in your home with the help of a grant.


No, you do not need to replace your radiators when you switch from a boiler to a heat pump. Both ground-source heat pumps and air-source heat pumps can operate alongside existing radiators. However, in some instances, a heat pump engineer may recommend that you invest in bigger radiators. To make the most out of your heat pumps, you need a large heat-emitting surface area.

However, getting new radiators for your heat pump should never be mandatory.

Your heat pump may cause a small degree of mess upon installation. The installation of ground-source heat pumps normally leaves a small amount of mess, due to the ground loop installation that is required to take place. This involves drilling boreholes and trenches, which could leave some general debris around the site. Plus, your property infrastructure may need to be modified to some degree.

No, you do not normally need permission to install a heat pump. Heat pump installations are normally considered to be a permitted development. As in, you can proceed to install a heat pump and don’t need to acquire planning permission first.

The only time you may need permission to install a heat pump would be if you live in a listed building or a conservation area. In this case, you should contact your council to check the requirements.

Heat pumps can still create heat energy on cold days. Even on the coldest of days, energy still exists outside and can be harnessed to the refrigerant liquid to turn into gas. As long as your house is well insulated, your heat pump should still produce enough hot energy to keep you warm.

The noise level of your heat pump depends on the location of your low-carbon heating system as well as the type of heat pump you’ve installed. Generally, heat pumps are quieter than heating systems that burn fossil fuels.


If you own a large house in Scotland, then choosing the right boiler is a decision that can’t be taken lightly, as it can greatly affect how your energy bills will look in the future. Don’t forget that it’s ultimately about ensuring comfort and warmth for you and your family.

With the energy crisis impacting so many Scots, it’s vital to start making informed choices that will give both efficiency and reliability. Whether you’re considering a combi boiler, system boiler or regular boiler, each has its own unique advantages which can suit different needs.

Remember that a warm home is a happy home. Although what you may have to pay initially for a new boiler may be daunting, you will have peace of mind and reap the benefits in the long term. Plus, grants like the ones provided by the ECO4 scheme can also provide financial relief, making energy-efficient upgrades more accessible to everyone.

In the end, it’s about finding the perfect balance between cost, performance, and environmental impact. So, take your time and weigh your options. If you make smart decisions, your home will stay cosy throughout the year.