Conventional gas boiler vs heat pump – which one is better?

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Conventional boiler vs heat pump

A conventional gas boiler burns gas (fossil fuel) to heat your home.  A heat pump takes heat from outside your home and distributes it inside. Boilers are still the most common system in the UK. But heat pumps are catching up due to their energy efficiency and low carbon footprint.

Very soon  gas boilers will be banned in new build houses.  It’s likely that from 2035, the installation of natural gas boilers will go the same way.  For homeowners, this means you’ll need to find an alternative, low carbon footprint method of heating your home.  A heat pump system is an obvious choice for this and we look at heat pumps vs boilers (natural gas furnaces) below. 

Heat pumps vs conventional boilers – heat output

Perhaps the most important thing when considering heat pumps vs boilers (conventional furnace) is how well the technology heats your home.  In general, boilers produce more heat.  A boiler is typically designed to run at 70°C while your average heat pump runs at around 50°C.  

Even though the output is lower, a standard heat pump is quite capable of heating a house in cold climates, even in sub-zero temperatures.  But it may require some changes to the heating system to work well.  If your radiators have been designed for a conventional boilers system they may need to be upgraded to run at lower temperatures.  You may also want to think about installing underfloor heating.  Likewise, to ensure that your home heats up adequately, you may need to upgrade your home insulation. 

We have covered these topics in other areas of the site.  If you are thinking of installing a heat pump we encourage you read further. 

Heat pump vs conventional boilers – efficiency

This is where heat pumps really come into their own. We generally use something called the coefficient of performance (COP) to measure how well an appliance turns energy into heat.  A natural gas boiler might achieve a COP of 0.9.  This means that 90% of the energy it uses (the gas it burns) is turned into heat.  A heat pump can easily achieve at COP of 4. This means that for every kW of energy it consumes, it produces 4 kW of heat energy in your home. 

The situation is a little more complicated as the final performance of the heat pump will depend on the climate and the time of year.  In colder temperatures, the heat pump will not be as efficient at heating your home.  A more accurate measure is the SCoP – the seasonal coefficient of performance.  This takes temperature fluctuations into account to give an average efficiency for the whole year and not just the colder months.  The average SCoP for a heat pump is between 2.5-4.  So this still makes it much more efficient than a gas boiler even when seasonal changes are taken into account.

Heat pump vs conventional boilers – carbon output

If you want to reduce your carbon output, then heat pumps are the better option.  The Energy Savings trust estimate that you can save around 2900kg/year of CO2 by switching from an old G rated boiler to an air source heat pump.  If you’re running an old-style, oil fired boiler this figure can increase to nearly 5000kg/year. 

Even for the most up to date gas boilers, you’ll still be producing a lot less carbon – up to 60% less in fact.  Over 10 years, you could save the equivalent carbon as 30 return flights between Heathrow and Madrid.

Heat pumps vs conventional boilers – installation

here’s no doubt that replacing a  new-for-old like-for-like boiler is a simpler operation than installing a heat pump.  The complexity of a heat pump installation will be depend on several factors

1. The type of heat pump you want
2. The type and size of your home.

The type of heat pump you want

Heat pumps come in several flavours depending how they capture the heat and how they distribute it in your home.  Some take heat from the air outside (air-source heat pumps) and some take heat from the ground (ground-source heat pumps).  Certain types of heat pump technology distribute the heat generated hot air pumped into your home (air to air).  Other types (called air to water heat pumps) heat a water source inside the home. These are the most common type of heat pump in the UK. They then circulate this water through a radiator system like a traditional gas boiler.

Some air to air systems have a reversing value which allows them to act as air conditioning and blow cold air in the warmer months.  We call these systems HVAC systems (which stands for heating, ventilation and air conditioning.  Conventional hvac systems are more common in the US and other countries than the UK.  They have a heating mode for the winter and a cooling mode for warmer months.  These are the best heat pumps for homeowners looking to keep cool in the summer.

Ground source heat pumps require a certain amount of outside space and are much more involved and expensive to install.  Air source heat pumps are cheaper to install, require less space and are the heat pump of choice for most homes in the UK.  

Breaking this down further, if you have a traditional heating system, air-to-air heat pumps are generally easier to install.  You will not need to touch your heating system, although you will need another solution for heating your hot water – typically conventional gas boilers or electric furnaces.  We call this a hybrid system.

Air-to-water systems are the most complicated to install as they interface with the heating system in your home. 

All types of heat pump will require an outdoor unit and a separate unit indoors.  To run an air source heat pump you will require at least 1M of space around the outside pump to allow the outdoor component to work efficiently.

The type of home you have

We’ve already touched on this in this article, but the type and age of your house will have a big effect on how difficult a heat pump installation will be.  For older homes (or larger homes), or for homes with an older heating system – you may need to make some upgrades to get your home to a comfortable temperature.  These might be quite simple, like replacing the radiators.  Or they may be more involved, such as increasing the outside wall insulation.  

This is an important factor in comparing the two and we encourage you to read further on this.

Heat pumps vs conventional boilers – cost

For many people, this is the big one.  At WeLoveHeatPumps we like to look at cost in two ways, installation costs vs running costs. 

Installation costs

While we know that the average cost of replacing a gas boiler is around £2000.  For a heat pump, it’s a bit more complicated.  An air source heat pump will cost anywhere from £3000 to £12,000 to install.  The good news that there are government grants available that can bring this cost down significantly. 

However, this upfront cost is just for the heat pump installation itself.  You will also need to factor in the modifications to your home and your heating system that you may need to make.  Please check out our article on ‘How much does an air source heat pump cost’ for more information on this‘. 

Running costs

In the long run, you will use less energy and  save money on your monthly bills with an heat pump.  However, at the time of writing (Nov 2023) electricity prices are still very high and your savings will be limited.  Analysts do expect electricity prices to drop however and when this happens the savings will increase.  

With regular maintenance, your heat pump should last around 15-20 years.  This compares well to the average ten year life cycle of a conventional system.

The Energy Savings Trust estimate that householders can save up to £930 per year by replacing an old (G rated) gas boiler with an air source heat pump.  For new (A-rated) gas boilers this figure is £320.

Conventional boiler vs heat pump – in summary

We hope this article has given you a good overview of heat pumps vs boilers. Whatever you think about heat pumps (and we love them) what’s clear is that the days of natural gas boilers are numbered.

One interesting technology in the pipeline is hydrogen boilers. These promise a more traditional heating system but with no CO2 produced. The technology is still in its infancy but shows great potential. But for now, if you’re looking to reduce your reliance on fossil fuels, getting a heat pump could still be your best decision.