Comparisons

Ground Source Heat Pump Comparisons

Ground source heating

What is the best heating system?

A ground source heat pump delivers the best low-carbon heating. It’s an affordable and eco-friendly alternative to fossil fuels such as gas, oil and LPG, which typically contribute to carbon emissions, air pollution and ultimately, play a part in climate change and global warming

Achieving a net-zero carbon future: Heating and hot water make up 25% of total energy use in British homes, equating to 15% of our greenhouse gas emissions.¹ To reduce the UK’s carbon emissions, the best heating systems are being encouraged by the government.

This starts with the ban of fossil-fuel heating in domestic new-build properties from 2025 – forming a part of the government’s plans to achieve net-zero by 2050. Gas and oil boilers are some of the fossil fuel systems that the government is banning from 2025.

What is a heat pump?

In brief, a ground source heat pump will:

100%
A ground source heat pump will provide 100% of heating and hot water requirements.
8°C – 12°C
Use the stable year-round ground temperature to deliver highly efficient heating, hot water and cooling.
A+++
Operate at a stable efficiency all year round. The Evo and Shoebox NX heat pump operate At A+++ efficiency.
20 years
The unit has a lifespan of over 20 years.
100 years
With a 100 year ground array lifetime.
0% VAT
Heat pumps for residential homes are eligible for 0% VAT.

What are the advantages of ground source heat pumps?

The advantages of ground source heat pumps vs. other heating systems include:

One of the lowest in carbon and running costs
Can be used to provide passive and active cooling
No planning permission required
Quiet operation
Safe and easy to operate
Simple to install
No noxious gasses or risk of combustion
No point-of-use emissions such as Nitrogen Oxide (NOx), Sulphur Oxide (SOx) or Carbon Dioxide (CO²).
Minimise ownership costs
Having a ground source heat pump means the property is much more energy efficient and less reliant on fossil fuels.
Alistair Mackintosh
Selfbuilder
Gas boilers

Gas boilers vs. ground source heat pumps

As gas is a fossil fuel, it releases carbon dioxide (CO2) – a greenhouse gas that contributes to climate change. To achieve the UK’s legally binding target of net-zero carbon emissions by 2050, it’s vital that fossil fuels, including natural gas, are phased out and replaced with renewable alternatives. Delivering a whopping 77% saving on emissions versus gas, see how ground source heating compares to the familiar boiler.

Gas boilers vs. ground source
Air source

Air source heat pumps vs. ground source heat pumps

Although both air source and ground source heat pumps are renewable alternatives to fossil fuels, they hugely differ in efficiency, running costs, carbon savings and durability.

Unlike air source heat pumps, the inherent efficiency of ground source heat pumps means they can deliver the lowest running costs of any type of heating system.

See air source vs ground source

Hydrogen vs. ground source heat pumps

Some people have proposed switching from gas to hydrogen, but in reality it’s not easy or straightforward to convert the gas network to hydrogen and there is no proven blueprint for this solution.

What happens in the next decade could be the measure of success or failure in achieving net-zero carbon. The longer we wait for hydrogen to create a solid solution, the closer we are to the tipping point.

Ground source has greater potential to decarbonise heating and; even better, it is tried and tested and ready to deploy right now.

Hybrid heat pumps vs. ground source heat pumps

A hybrid heat pump system, also known as a dual fuel system, couples renewable energy with fossil fuels to provide heating and hot water to a home. A hybrid can be made up of a heat pump and a fossil fuel heating system, but in this context, we’ll look at how a hybrid – made up of an air source heat pump component and a gas boiler component – compares to a single ground source heat pump system.

A hybrid heat pump system is designed to meet the building’s heating and hot water requirements, whilst reducing carbon emissions through the use of renewables. It involves the installation of both the fossil fuel heating system component and the heat pump component.

Firstly, how exactly does a hybrid heat pump work? Hybrid systems can have flexible heating modes, which include:

  • Switch hybrid mode

    Where the entire heat demand for a certain period is met by the boiler if the heat pump component cannot meet the demand

  • Parallel hybrid mode

    Where the heat pump can contribute some heat during that period.6
Cost of hybrid heat pumps vs. ground source

Hybrid heat pump

It’s important to consider all of the costs associated with a hybrid heat pump, including initial, operating and replacement costs. This is important when comparing the technology to a singular ground source heat pump, as ground source tends to be cheaper in the long run.

Initial costs
The initial cost of a hybrid system all depends on the scenario, such as if you already have a system. For example, if you would like a hybrid system and you already have a gas boiler installed, that could mean you only have to account for the cost of the air source component. If you were to install both components together from scratch, the total cost of a hybrid domestic heating boiler with its associated air source heat pump can be between £7,500 to £15,000. However, this will vary depending on the type of project and heating requirements.7
Operating costs
Fuel costs will be somewhere between the costs of a gas boiler and an air source heat pump (depending on the operating split). However, some of the other operating costs are doubled up. For example, you end up paying two standing charges – one for electricity and one for gas. You also need annual servicing and regular maintenance to check that the gas boiler is combusting fuel safely.
Lifetime or replacement costs
One of the main issues with a hybrid system is that it will incur twice the replacement costs of relatively short-lived appliances typically every 10-15 years for both appliances.
Cost of hybrid heat pumps vs. ground source

Ground source

The initial cost of a pure ground source heat pump conversion from mains gas is currently more expensive than an air source heat pump/gas hybrid. However, the ground array infrastructure has lifetimes in excess of 100 years and because ground source heat pumps are typically located indoors they have longer lifetimes of 20-25 years. Once you model the costs over longer periods and account for fuel consumption, standing charges, servicing, maintenance and replacement costs then ground source heat pumps become the lowest cost option. The long-lifetime, long-term savings and lack of maintenance that comes with a ground source heat pump soon make up for the initial cost, which is a significant advantage in the context of mass deployment.

Carbon emissions of hybrid heat pumps vs. ground source

Hybrid heat pump
In terms of emitting carbon emissions, a hybrid heat pump still has the disadvantage of burning fossil fuels. Although this is reduced by the heat pump component, it will still produce a higher percentage of emissions versus a single ground source heat pump system. A study published in 2018 by the UK government into the effectiveness of hybrid heat pumps suggests that, on behalf of the heat pump component of the system, the carbon emissions intensity will improve over time. This aligns with the rapid decarbonisation of the electricity grid, as that’s where a heat pump gets a proportion of its power from. The scenario is based on a typical semi-detached house, where the hot water demand is met by the boiler component of the hybrid heat pump. However, most hybrid systems have to choose between saving carbon and reducing bills and it is not clear how the controls are to prioritise a mixture of these benefits. Air source heat pumps are far lower carbon but have higher running costs. If the system prioritises carbon, the gas boiler will only run for 5% of the year when the electricity system is high carbon. If they prioritise running costs, the split will be more like 50/50 when electricity is cheap – if on a time-of-use tariff.
Ground source
This projection of decreased carbon intensity over time is even better reflected in ground source heat pumps. To put this into perspective, the study suggests that by 2050, heat pumps could be left with a carbon intensity of around 00.01kgCO2/kWh.8 In fact, ground source heat pumps coupled with smart meters and flexible tariffs can produce bill savings of 25% and carbon savings of 77% compared to mains gas.

Oil & LPG boilers vs. ground source heat pumps

Oil and liquefied petroleum gas (LPG) is traditionally the go-to alternative fuel for buildings that are not connected to mains gas. However, prices of oil continue to fluctuate against a backdrop of growing global concerns – particularly energy security.

Meanwhile, heat pump technology has evolved, along with accessible funding streams and affordable running costs. Ground source heat pumps have therefore become a more viable and preferred option for off-gas areas.

Add to this the pressure of government plans to ban fossil-fuel heating systems in new builds from 2025, and it looks like oil and LPG boilers could be phased out entirely by 2050.

Disadvantages of oil & LPG boilers

Vulnerable to energy price hikes and fluctuations, bulky and unsightly fuel storage tank, highly flammable, reliance on fuel deliveries, possibility of fuel theft, pay for the energy upfront all in one go, complicated installation, contributes to air pollution through the emission of particulates, Nitrogen Oxide (NOx) & Sulphur Oxide (SOx), high carbon content.

Running costs of oil boilers vs. ground source

Oil boilers
There are a number of factors that make oil prices volatile. The price of crude oil is particularly sensitive to the laws of supply and demand, which can vary worldwide with fluctuations in the economy, political unrest and extreme weather events. Supply can be influenced by the Organisation of Petroleum Exporting Countries (OPEC), who will cut output in order to strengthen prices by reducing supply.
Ground source
Ground source heat pumps can save occupants around 30 – 50% in running costs compared to oil boilers. Electricity prices, as used to drive a ground source heat pump, do not suffer from the same volatile prices. Aside from a ground source heat pump’s inherent efficiency, delivering typically 3 to 4kW of free heat energy for 1kW of electrical energy and making the use of off-peak tariffs in well-insulated buildings, the running costs of ground source heat pumps are significantly lower than oil boilers. That is a benefit you wouldn’t see from oil.
The savings on our energy bills compared with oil is fantastic and our house value has increased as a result of the installation - we’re over the moon!
Stephen Chidgey
Homeowner

Maintenance of oil boilers vs. ground source

Oil boilers
Oil boilers use combustion in the heating process, so they must be serviced and maintained correctly. Failure to do this can lead to major health risks, such as the production of poisonous gases like carbon monoxide.
Ground source
As ground source heat pumps do not use combustion, there is no risk of poisonous gases being emitted. Moving parts are kept to a minimum and are non-serviceable, so maintenance is minimal. This makes ground source heat pumps significantly cheaper to maintain, saving occupants or ground source owners money by eliminating the need for annual servicing.

Lifetime of oil boilers vs. ground source

Oil boilers
These days most oil boilers are condensing boilers, as they provide a much higher efficiency than non-condensing boilers. Oil-fired condensing boilers typically have a shorter life (7 to 10 years) than traditional non-condensing boilers, as the heat exchangers can rot out quickly due to the acidic condensate.
Ground source
Ground source heat pumps generally have a design life of approximately 20 years due to their lack of moving parts and secure installation inside the home.

Storage of oil vs. ground source

Oil
Oil supply for oil boilers must be stored on site. It’s generally stored in a bunded oil tank, which is basically a small tank within a large tank. The larger tank is able to hold 110% of the capacity of the smaller tank. This is used to protect the surroundings of the tank from any oil spills of leakages. When storing oil, there needs to be sufficient space and access to the tank. With OFTEC health and safety regulations stating that it must be located within 1.8m of the building, the unsightly oil tank can take away from the aesthetics of a property. As well as that, security measures against theft need to be considered if large volumes of oil are being stored on site.
Ground source
As ground source heat pumps run on electricity, no fuel storage or deliveries are required on site – allowing for additional space, peace of mind, and preventing the need for storage that many people feel is an eye sore.

Carbon emissions of oil boilers vs. ground source

Using the carbon intensity factors proposed for SAP 10, an oil boiler emits almost five times as much carbon as a ground source heat pump.

In terms of carbon emissions, there is no justification for the use of oil or LPG boilers when far more appealing and renewable heating options are available. This is why the government is phasing out oil boilers in favour of lower carbon renewable heating systems such as ground source heat pumps.

Can a heat pump replace an oil boiler?

Yes. For older properties that are not especially well insulated, Kensa will help you to establish whether the existing heating system and existing insulation levels will be compatible with a ground source heat pump, or if your heating distribution system and energy efficiency measures require any upgrades.

If you are undecided on whether you should upgrade your radiators or insulation levels, you can run a trial over a heating season. To do this, we recommend you turn down the flow temperature of your existing boiler to 50°C and run the system through the winter heating season to mimic the output of a ground source heat pump system.

If you find you can maintain your required comfort conditions at this lower flow temperature, then you have proved that your existing heating distribution system and the current heat loss of your property is compatible with a ground source heat pump installation – without any upgrades required. If you were not satisfied with the comfort levels then we advise you to upgrade your radiators, and improve the insulation levels in the property prior to installing a ground source heat pump.

What is the difference between ground source heat pumps & geothermal heating?

Geothermal heating vs. ground source heat pumps

There is often much confusion when it comes to comparing ground source heat pumps to geothermal heating. Some people use the terms interchangeably, but there are key differences.

Ground source heat pumps, like those manufactured by Kensa Heat Pumps, generally take heat from 1.2m – 200m depths. In this zone, there is a large amount of low-grade energy available, which needs a heat pump to upgrade this to more useful temperatures.

The reason geothermal heating is often confused with ground source heating is that both ultimately harness heat energy from the ground to provide heating and hot water to buildings.

However, the main differences are where the heat originates and the application the heat will be used for.

  • Geothermal heating

    Uses heat directly from the earth’s core, such as hot springs, geysers and volcanic hot spots.

  • Ground source heat pumps

    Absorb the sun’s energy stored in relatively shallow ground and upgrade this for use in domestic and commercial applications.

What is geothermal heating & how does it work?

Geothermal heat comes from the earth’s core; ‘geothermal’ literally means ‘earth’s heat’. It uses heat directly from drilling deep or shallow sources emanating from the earth’s core, such as hot springs, geysers and volcanic hot spots.

Borehole drilling for geothermal heating can often be drilled to depths many kilometers below the ground. In the UK, you have to go down 500m – 2500m before there is any appreciable input from the earth’s core. Geothermal typically needs to be deployed at large scales to make it financially viable.

Geothermal systems operate at temperatures of 120°C – 300°C and therefore do not necessarily need a heat pump to upgrade the heat, nor a ground loop system.

Large-scale plants and communities tend to use geothermal energy over ground source heat pumps.

Why does the difference between geothermal & ground source matter?

When you drill a deep geothermal hole, it’s not always clear what the conditions will be like further down. Inevitably, this could determine how well the system will work.

However, ground source heat pumps absorb energy at shallower depths, which means there is a much higher level of certainty around the conditions you will find.

What are the other common names for ground source heat pumps?

The following terms are sometimes used when referring to ground source heat pump installations, and can be misleading and technically inaccurate due to their ‘geothermal’ references:

Geothermal heat pumps
GeoExchange heat pumps
Earth-coupled heat pumps
Deep geothermal
Enhanced geothermal systems
Geothermal, direct use
Hydrothermal
Hot rocks
Hot dry rocks
Geothermal power
Disadvantages of biomass heating compared to ground source heat pumps:

Biomass vs. ground source heat pumps

Space required for fuel storage, reliance on regular fuel deliveries, high maintenance compared to ground source heat pumps, planning permission required due to emissions, contributes to air pollution through the emission of particulates, Nitrogen Oxide (NOx) & Sulphur Oxide (SOx).

References

1. UK housing: Fit for the future? Committee on Climate Change, 2019

2. Hydrogen for Heating? Prof. David Cebon, University of Cambridge, as cited in Hydrogen: a decarbonisation route for heat in buildings? LETI, 2021

3. Is hydrogen the solution to net-zero home heating? The Guardian, 2020

4. Hydrogen: a decarbonisation route for heat in buildings? LETI, 2021

5. What is a Hybrid Heating System? Boiler guide

6. Hybrid heat pumps final report, BEIS, published 2018

7. What is a Hybrid (Dual Fuel) Heat Pump System? IMS Heat Pumps

8. Hybrid heat pumps final report, BEIS, published 2018