Heat Pump vs Gas Boiler: Which Is More Efficient?

There aren’t many homes with air source heat pumps installed at the moment and customers, looking for comparisons, ask other customers how much does your heat pump cost to run a month. 

They expect that if they get a heat pump it’s going to cost a similar amount.  But almost always, this is going to be quite a different amount.  Here are the things to think about when comparing these systems.

Heat pump vs Gas boiler: which is more efficient?

A gas boiler typically has an efficiency of 90%, whereas an air source heat pump has an efficiency up to 400% mainly because heat pumps also have a lower flow temperature than a gas boiler. But efficiency for a heat pump is more varied over the year than a boiler which is consistent. Also, heat pumps run on electricity which is more expensive than gas.

heat pump vs gas boiler, which is more efficient?

If we have a heat pump that doesn’t perform so well due to being older technology or just poor installation, and its efficiency performance is low, say 2.5 (which means it gives out 2.5 times as much energy than what it uses), the running costs can end up being more than a poorly installed gas boiler.

Are heat pumps more efficient for larger properties?

Larger properties with more than 3 bedrooms will most likely require more than one air source heat pump to heat the house effectively. 

In the colder months, the unit may not be able to provide enough heating on its own and you would need a second unit.  This makes them less efficient. 

Compare this to a gas boiler, which can perform well in larger properties simply by increasing the kW output and only a slight increase in the size of the appliance.

Electricity vs Gas price efficiencies

Heat pumps require electricity to run whereas boilers mainly run on gas in this country.  So, the efficiency of each system will also depend on how much these fuels cost. 

Historically, electricity prices have been 3 times more expensive than gas.  But a heat pump is 3 to 4 times more efficient than a gas boiler which means it should still be cheaper to run.

The other advantage electricity usage has over gas is the variable prices depending on the time of use

For example, if there is plentiful electricity being fed into the grid by renewable energy, the unit price of electricity comes down and as a result the heat pump becomes cheaper to run. 

You can use this cheaper rate to charge up the hot water storage cylinder for example.  You don’t have this flexibility with gas prices.

Other technologies like solar power and storage batteries all work with electricity and as the technology advances in these, you should be able to use them to power the heat pump too, making them more cost efficient.

Three main factors decide what the running costs of a heat pump will be: The size of the property – larger houses cost more to heat; how good the insulation is – so the heat pump can run at lower temperatures; and finally, how well the system is designed and installed.   

The last variable directly decides how efficient the heat pump is.

Advantages of gas boilers over heat pumps

Most properties have combi boilers installed which are well known to save space.  They provide hot water and heating in one compact unit.  Houses have been designed around this reality. 

Most properties don’t have the space to put an air source heat pump outside the house, as well as a hot water storage cylinder inside the home.  Let alone extra space required for potentially larger radiators and pipes. 

Modern gas boilers are also extremely quiet when running, night or day.

The cost of a gas boiler installed is much cheaper than an air source heat pump.  Compare £2500 for a brand new gas boiler to an average £10000 cost of installing an air source heat pump. If government grants are not available, is the better efficiency of a heat pump worth the extra upfront cost? 

cost of a heat vs a boiler

Efficiency of gas boiler and heat pump sizes

Oversized gas boilers in properties has been a reality in the industry for decades with manufacturers making bigger boilers.  Heat loss calculations have rarely been done accurately by engineers. 

Oversized boilers mean the appliance runs inefficiently costing you more money.  Heat pumps will potentially have the same issue, so it’s critical that an in depth heat loss calculation is done beforehand.

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*The information in this article should be used for general guidance only and not as financial or health advice.  Full details are on the link in the footer to our disclaimer page.  Always discuss your requirements with a competent and suitably qualified professional before undertaking any work.