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Are Hybrid Heat Pumps the Answer to Achieving Net Zero by 2050?

23rd Jun 2022

Bronte McClelland
By: Bronte McClelland
Updated: 23rd June 2022

hybrid heat pump net zero solution

The British public can no longer receive financial support for hybrid heating solutions. This makes it increasingly difficult for people to make the switch to renewable energy options and ultimately could have a disruptive impact on the UK government's goal to reach Net Zero by 2050.

The UK government wants to phase out gas boilers, starting in 2025 with banning gas boilers from all new builds. However, a Boiler Guide survey from October found that the British public isn't ready to give them up. So what is the solution to this clash in interests? According to a new report from the Heating & Hotwater Industry Council (HHIC), hybrid heating systems could be the answer.

Hybrid heating systems are a combination of two or more technologies that generate heat to provide a building with heating and hot water. The most common type of hybrid heating system, and what we'll be referring to in this article, is a 'hybrid heat pump'. This is usually an air source heat pump combined with a gas condensing boiler, however, a ground source heat pump and other fuel types such as oil and liquefied petroleum gas (LPG) may be used instead.

This means hybrid heat pumps are a good middle ground, as people can reduce their carbon emissions and adapt to new technology without having to prematurely give up their boiler and home-heating habits.

However, since the Renewable Heat Incentive (RHI) scheme stopped accepting applications in March this year, there are now no subsidies available for installing hybrid heating systems in the UK.

The Boiler Upgrade Scheme (BUS), the replacement for the domestic RHI, was introduced in April 2022. The BUS is meant to help homeowners upgrade their heating systems to a low-carbon option through financial support. The scheme offers grants up to £6,000 and will run for 3 years until 2025.

Specifically, the BUS offers grants of £5,000 to install air source heat pumps and biomass boilers, and grants of £6,000 for ground source heat pumps as these tend to be much more complex and expensive to install. However, the issue with the BUS is that it only provides funding for heating systems that provide 100% of the hot water demand and space heating. Therefore, hybrid heat pumps do not meet the criteria to be included in the scheme.

Despite the availability of these schemes, the current demand from consumers for low-carbon heating is low. This is due to a multitude of reasons, such as installation disruption, up-front costs, and minimal running cost savings as the price gap between gas and electricity is still high.

This low demand is concerning. About 85% of British households use gas boilers for heating and hot water. Fossil fuels used in homes accounts for more than a fifth of the UK's carbon emissions, making it one of the most polluting sectors.

Considering the UK's Climate Change Committee's (CCC) reduction targets of 68% by 2030 and 78% by 2035 (when compared to levels from 1990), this will certainly be a challenge for Britons. HHIC's report states that a near-total decarbonisation of UK housing is required to hit these targets.

There is an urgent need to deliver a range of low-carbon heating solutions in order to help reach these targets in time. Hybrid heat pumps, in conjunction with support in policy changes, can help tackle this issue.

Even though a full heat pump system is a great choice for homeowners who want high levels of efficiency and lower carbon emissions, it is not a viable option for all homes in the UK.

Firstly, the UK is known for having some of the draughtiest homes in Europe, with about 25 million homes having inadequate insulation. By 2035 all existing homes will need to achieve an Energy Performance Certificate (EPC) band of C or higher, to ensure that they are able to support the lower temperatures used by a full heat pump system.

In order to achieve this, many homes will need to implement basic measures to reduce heat loss. Three relatively simple measures that can significantly help insulate homes are double-glazing, cavity wall insulation, and a minimum of 200mm of loft insulation. The Energy Saving Trust has estimated the energy savings by insulation measures. You can see this as well as the percentage installed in England and Wales in the graphs below:

Reduction in Heat Loss for Different Insulation Measures Graph

Percentage of Insulation Measures Installed 2009 vs 2020

However, unfortunately these insulation measures do come at a price and add to the total up-front costs of installing a full heat pump system. While it is still advised to implement these measures over the long-term, installing a hybrid heat pump as opposed to a full system means you do not need to make and pay for these changes all at once.

A hybrid heat pump can yield up to 55% carbon savings as an average across different building types, without the home modifications and installation disruption that comes with a full heat pump system.

Another issue with full heat pump systems is space. Data provided by HHIC shows that 80% of the 1.7 million UK annual gas boiler sales are combi boilers. One of the main advantages to this type of boiler is that it saves space as the addition of a hot water storage tank is not needed. A heat pump on its own would require the installation of a hot water tank, costing more money.

Percentage of Boiler Types Sold UK Pie Chart

Heat pumps also require space outdoors, especially ground source heat pumps. Hybrid heat pumps are available in more compact sizes with the option to be wall-hung, making them more suitable for smaller homes.

One potential concern with heat pumps in general has been their level of variability in performance. However, recent studies discussed in the HHIC report have shown that the addition of smart controls can solve this problem by taking into account household behaviours and the outside temperature. The Electrification of Heat (EoH) trial did not use smart controls, while the Passiv UK trials did. The results are shown in the following graphs:

Data on smart controls with hybrid heat pumps
CoP = Coefficient of Performance
Source: HHIC report

Furthermore, this data validates the theory that 80% of a home's annual heating can be provided by a hybrid heat pump. It should be noted though that with a combi hybrid this does not cover the provision of domestic hot water (DHW), as the boiler would still heat the DHW all year round.

Finally, some would argue that there is no need for heat pumps due to the government's focus on switching from natural gas to hydrogen. While this is an important step in reaching Net Zero, it does not mean the two options have to be mutually exclusive.

Chris Jackson, the chair of the UK Hydrogen and Fuel Cell Association stated that "even within the hydrogen and fuel cell community the feeling is that the fix can’t be to keep British housing stock the way it is and simply replace natural gas with hydrogen.” Bigger and more immediate changes need to be made in order to reach Net Zero by 2050.

As the technology for 100%-hydrogen boilers is still being developed, hybrid heat pumps are a solution that can already be implemented. On top of this, it is easy to adapt to either a full heat pump system or use it alongside a hydrogen boiler in the future.

Hybrid heat pumps with their impressive energy efficiency and reduced carbon emissions show a lot of potential for the future of heating British homes. However, changes in policy need to be made in order to support both homeowners and installers alike to achieve a low-carbon future.

Bronte McClelland

About the author

Bronte McClelland

Brontë is one of our resident home heating experts. She has expertise in writing about renewable energy and heating systems, and continues to stay up to date with the latest trends and technology.

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