Gas Boilers Vs. Ground Source Heat Pumps

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.

A big benefit of a ground source heat pump is that it future-proofs properties – both in terms of sustainability and conforming to regulation. From 2025, the government has confirmed that gas boilers will no longer be an option for new builds. They are even set to commit to cutting carbon emissions by 78% by 2035, meaning that a significant amount of gas boilers will have to be ripped and replaced. In fact, to tackle the climate crisis, it’s possible that by the mid-2030s, the installation of new gas boilers will be banned entirely.

It’s not just the low-carbon reasons. Renewable heating systems, such as ground source heating, come without the flammability, risks, flues and regulations associated with gas. Using a non-flammable refrigerant, heat pumps such as the Shoebox also avoid the risks, servicing and expenses of fossil fuel systems.

Sooner or later we are all going to have to reconsider how we heat our homes, so we’re encouraging anyone with the opportunity and budget to invest in ground source heating to do so sooner. This is because there are funding streams available right now – such as the Boiler Upgrade Scheme, which offers grants of £7,500 for those installing ground source heat pumps.

It’s safe to say that the majority of households are familiar with gas boilers. But with all of these vital targets considered, something is going to have to take the commonplace position of the gas boiler for most of our homes – this is where heat pumps come in!

A gas boiler heats water by pumping it into pipework over a series of gas flames. Just like liquid in a pan, the water is heated up as it passes the flames. It is then used to deliver central heating and hot water to the home. There are different types of boilers, such as combi boilers, which give you instant hot water – meaning you don’t need a hot water tank.

As gas is a fossil fuel, it releases carbon dioxide (CO2) – a greenhouse gas that contributes to climate change. The combustion of fossil fuels also releases particulates, NOx and SOx into the atmosphere that contribute to global warming and air pollution.

A ground source heat pump is an electrically-powered heating system. Using buried pipework filled with a heat transfer fluid (usually glycol), the system absorbs low-grade heat energy from a renewable energy source, such as the ground or water. The heat pump then compresses this heat energy to raise its temperature.

Heat exchangers transfer the additional heat energy from the glycol fluid to the water piped through the home’s heating distribution system, upgrading this to a higher temperature. The newly heated hot water can be used for space heating delivered by radiators or underfloor heating, and also for domestic hot water stored within a cylinder.

The underground pipework, known as a ground array, can be installed on an individual or communal level – providing a sustainable and naturally replenished source of heat for either a single home or a whole street. Kensa has pioneered an infrastructure that mimics the existing gas network, facilitating the installation of ground source heat pumps on a larger scale. This is known as a Shared Ground Loop Array.

Gas heating has been long recognised as a cheap source of heat although the running cost of gas fluctuates with many factors, such as market reforms or world events that affect the availability of gas – pushing prices up or down. For example, as of December 2020, prices fell in the 12 months previous, which meant the fuel is currently very low cost – but this changes frequently.

Ground source heat pumps compare favourably with gas and were very similar until very recent gas price drops. However we expect the running costs of ground source heating to further drop with the adoption of smart methods such as load shifting. This means, using smart controls and time-of-use tariffs, the ground source heat pump can automatically run when electricity is low in cost and carbon. This is usually in line with periods of renewable electricity production from sources such as wind and solar.

Load shifting means you can avoid expensive times, and even take advantage of the fabric of the building. For example, if you like to have your heating on at 20ºC by 5 pm, most heating systems would turn on at 4.30 pm and gradually bring your house up to temperature for, say, when you get home from work. However, if this system looks ahead at energy prices and realises it will be expensive between 4.30 – 6.30 pm, it might turn the heating on at 2 pm – bringing the temperature up to 22ºC and cooling down to the perfect 20ºC when you return.

Smart controls learn your heating preferences and devise a customised heating schedule for your home that provides optimum comfort, whilst saving you money. Heat pump projects such as Energy Superhub Oxford estimate that this could deliver savings of up to 25% compared to a standard ground source heating system. On average, this means that ground source heating can be cheaper than gas. A win for the environment and for our pockets.

The savings can increase even further when using physical energy storage such as a heat battery, which means you can store the heat following consumption at off-peak times, and use it when required.

As for lifetime costs, an average boiler will need replacing every 10 to 15 years, whereas ground source heat pumps will typically last 25 years and do not require annual servicing – saving you even more. The ground array pipework used to extract the heat energy will last for 100 years, so installing this infrastructure is a one-off investment to provide heat for generations. Lastly, if you disconnect the property from gas completely, you save yourself the gas standing charge.

Modern condensing gas boilers can be around 90% efficient. This means that 90% of the energy used by the boiler goes to heating the home, while the remaining 10% is waste heat that is passed through the flue to the outside. The heating system isn’t as efficient as it could be because of this wasted heat.

Not even home improvements would make a huge difference to the system’s efficiency. The only real benefit of adding energy efficiency measures, such as insulating the property, is that you’re using fewer kilowatt-hours (kWh) of energy per year. On the other hand, energy efficiency measures coupled with a heat pump give you a double win; you can actually go back and improve insulation to improve the efficiency of the system.

Ground source heat pumps can be 300 – 400% efficient, which means they can deliver three to four times the amount of energy they consume from electricity. When multiple properties are linked to a shared ground array system, there is even a chance to increase this performance by utilising waste heat from applications such as server rooms and supermarkets – the options are endless.

When comparing ground source heating to gas, it’s important to consider the relationship between flow temperature and efficiency. A ground source heat pump operates at a lower flow temperature than a boiler, but that’s certainly not to say the heat pump doesn’t reach the building’s required temperature; it may just require a larger surface area such as underfloor heating or a larger radiator.

For example, a room that needs 500W can be heated just as quickly by a larger radiator operating at 50°C as by a small radiator operating at 70°C. The lower the temperature is, the higher the efficiency of the system.