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Hybrid Heating System – What is a Hybrid Heat Pump and Should You Get One?

Hybrid heating system

Hybrid heat pumps are an excellent way of improving the energy efficiency of your home without ripping out your whole heating system and replacing it with more efficient technology.

Hybrid systems combine renewable and traditional heating technology into a single system, which operates flexibly and brings the best of both worlds to your home.

Able to provide both space heating and hot water, they can be a great choice under the right circumstances.

So, is a hybrid heat pump system the right choice for you? Let’s find out.

What is a hybrid heating system?

What is a hybrid heat pump?

First of all, let’s get a better understanding of exactly what a hybrid heating system is.

Fundamentally, a hybrid heating system is a system that makes use of two different heating technologies to provide hot water and heating to a property.

Normally, this will be a heat pump (often air source but could be ground source or water source) fitted alongside a fossil fuel boiler, running either on mains gas, oil or LPG.

Hybrid heating systems can be programmed to make use of electricity at times when this is cheaper, switching to the backup fossil fuel boiler at times of high heat demand or when the economics or carbon emission savings demand it.

Hybrid heat pumps can be a good choice for people who are looking to improve the energy efficiency of their home, but for which a standard heat pump is unsuitable.

Alternative heating systems

Alternative heating system.

If you are considering installing a hybrid heat pump, it’s likely that you have an existing traditional heating system and are considering how far down the green route to go.

You could stick with fossil fuels, but that’s bad for the planet and does nothing to help mitigate climate change. It’s also likely to become more expensive as time goes on, with renewable energy technologies improving and becoming cheaper all the time.

The best approach to go for to minimise your carbon emissions and take advantage of the financial incentives that are available at the moment, is to install a stand-alone heat pump. However, stand-alone heat pumps are not always the best solution and in some circumstances may not be appropriate at all.

That’s where a combined hybrid approach could come in.

Let’s compare some of the alternatives.

Hybrid heat pump vs heat pump

When does it make sense to use a hybrid heat pump system as opposed to a stand-alone heat pump? There are several circumstances where this could be the smart choice.

You are on mains gas and gas prices are low

Modern gas boilers have become extremely efficient at providing heat and hot water with many condensing boilers having efficiencies upwards of 90%.

Such impressive efficiency figures, combined with the relatively low cost of mains gas, mean that many people who are lucky enough to be on the gas grid continue to enjoy relatively low-cost heating and hot water compared to people living in rural areas.

If you are on the gas grid, you might not save much money by installing a stand-alone heat pump. You would of course save in terms of your carbon emissions, but not many of us are in a position to put carbon emissions ahead of financial concerns – you can be as green and eco-friendly as you wish but if that means not being able to put food on the table, you have to refocus your priorities.

Rather than taking an all or nothing approach, installing a hybrid heat pump system could bring you the best of both worlds.

Some people set the heat pump part of their hybrid system to run only their space heating, typically making use of underfloor heating, which is very efficient in combination with a heat pump. The gas boiler can then handle hot water only, which could be better cost wise because the efficiency of heat pumps reduces slightly at higher output temperatures.

Your home has a very high heat demand

Simply put, the heat demand for a building is the amount of energy required to maintain it at a comfortable temperature.

The heat demand of a building can be estimated using multiplication factors, essentially rules of thumb, that apply to different categories of building.

Heat demand can also be estimated using records of the actual energy delivered to a property over the course of a year. This information should be available on your gas or electricity bill.

The less well insulated your building is, the higher its peak heat demand will be and therefore the larger the heat pump or boiler needs to be. This is for the obvious reason that a lot of heat will escape through the fabric of the building.

In addition to the heat required to maintain room temperature at a comfortable level, there is also a heat requirement for hot water.

If you know roughly how much water you use, it is straightforward to apply a standard conversion factor that will tell you the heat demand for hot water during a typical year.

If you are not on a water meter, you can estimate the amount of water you use by multiplying the number of people who live in the house by 142, which is the number of litres a typical person uses in the UK each day.

Multiply again by a factor of 0.0585 to determine the number of kilowatt-hours of energy required to heat your hot water (this assumes that water is supplied to your home at a temperature of 10°C and is heated to 60°C).

Of course, all these calculations can get quite involved and for this reason it is recommended that you consult a qualified professional to help with the design of your heating system.

Just know that if you live in a poorly insulated property or have a large family, your heat demand is likely to be high. This won’t always mean that a stand-alone heat pump is unsuitable and that a hybrid system is necessary, but you should take care to properly size your system and know what to expect in terms of cost upfront.

You are on a tight budget

Heat pumps are still more expensive to buy and install than traditional heating systems such as gas boilers. Everyone is hoping that this will change soon, but for now you’ll need deeper than average pockets to be able to afford one.

The Renewable Heat Incentive (RHI) helped to mitigate these larger upfront costs, but the incentive scheme has ended now. The Boiler Upgrade Scheme (BUS) is available in England and Wales but does not cover hybrid systems. In Scotland, there is no replacement for the Renewable Heat Incentive scheme as yet.

It is unclear whether even the zero VAT rating announced by Chancellor Rishi Sunak for energy-saving materials applies to hybrid systems. If government takes a similar view that under the Boiler Upgrade Scheme, then it’s unlikely that it will.

For these reasons, unless you are in the fortunate position of being able to put your green principles ahead of financial concerns, your wallet might thank you for sticking to traditional heating technologies for now.

Particularly if you are on the mains gas grid, which despite the recent price rises, continues to offer relatively good value for money when compared to more environmentally friendly alternatives.

Hybrid heat pump water heater vs gas

Another way to compare hybrid heat pumps is against the fossil fuel alternatives. For the sake of argument, let’s think about hybrid heat pumps compared with a traditional gas boiler that uses mains gas.

As we have touched on above, hybrids offer a middle path for those wanting to reduce their carbon footprint whilst allowing the flexibility of having a backup system for those days of the year when heat demand is particularly high.

If you have a very high heat demand and are not particularly concerned with reducing your carbon emissions, then you could probably stick with gas for now.

But, if you want to hedge against gas prices going up over time and can afford to install a hybrid heat pump now, this could offer the best of both worlds. Particularly if you have your system set up to use the heat pump when electricity is cheapest, with the gas boiler taking over at times when electricity is expensive.

Alternatively, you could run your space heating exclusively using low temperature radiators or underfloor heating in conjunction with the heat pump and heat your hot water solely using gas.

This is a nice setup because it plays to the strengths of each technology. The gas boiler can supply hot water quickly and efficiently, with the air source heat pump operating at relatively lower temperatures. This allows the heat pump to make use of the large heat transfer area available in underfloor heating to provide warmth at the lower temperatures it needs to operate at maximum efficiency.

Hybrid heat pump pros and cons

That was a lot of information to take in, let’s tease out the main pros and cons of hybrid heat pumps.

Advantages of hybrid heat pump systems

  • Able to cope with high heat demands.
  • Able to make use of cheaper electricity to provide warmth.
  • Reduce greenhouse gas emissions without sacrificing comfort.
  • Suitable for older houses or less well insulated properties.

Disadvantages of hybrid heat pump systems

  • Still contribute to global warming.
  • Do not qualify for financial incentives offered through the Boiler Upgrade Scheme (BUS)
  • More complex control requirements to achieve optimal efficiency due to the two-system approach.
  • More expensive to install than a fossil fuel-only boiler.

So, are hybrid heat pumps any good?

It depends on your specific circumstances, but they are a good option if you need the security of a backup boiler for very cold days.

With the right design and system controls they can be more efficient, cheaper to run and have lower carbon emissions than a fossil fuel alternative.

Summary

Hybrid heating systems are simply systems that make use of two or more heating technologies to provide a comfortable living temperature in your home and hot water for bathing and washing the dishes.

A hybrid heat pump can be air source, ground source or water source and typically operates in conjunction with a fossil fuel powered boiler.

Hybrid heat pumps offer the best of both worlds by allowing the heat pump to operate at maximum efficiency when the conditions are right.

This is when the temperature difference between outside and inside is lower, which means the heat pump does not have to work too hard at reduced efficiency. It can also be cheaper to run the heat pump when electricity prices are lower and the heat pump can heat the house more economically than the fossil fuel boiler.

One downside of hybrid systems is that they don’t necessarily qualify for the financial incentives offered by government to encourage the uptake of renewable heating technology. This is because they still have a fossil fuel component and therefore release carbon dioxide to the atmosphere, contributing to climate change.

Although hybrid systems still contribute to global warming, they are better than a fossil fuel-only approach and also have the benefit of a backup system for very cold days when a heat pump might not manage to provide sufficient heat at reasonable cost.

If you are interested in the possibility of installing a hybrid heat pump in your own home, please take a look around the rest of this website to learn more about heat pumps in general.

When you are ready to enter the market and find an installer, I’d recommend reading through our article about how to find a heat pump installer, which guides you through the process and includes advice on how to assess the credentials of a potential installer, including some questions to consider asking before you engage them in your project.

There is a directory of installers on our installers page, which you can use to find installers in your area who might be able to help you. These are provided as a starting point for your search and Heat Pumps Scotland does not endorse them in any way. Please conduct your own due diligence to ensure you employ a suitable installer.

River Tay Heat Pump

Heat pump bid in trouble as funding put in danger by slipping project deadlines.

Introduction

Growing opposition to the River Tay Heat Pump District Heating Scheme risks derailing the most promising initiative of its kind and dashing the hopes of local residents and businesses who would benefit from its success. The scheme would provide cheap, green heating to homes in one of the most deprived areas of Perth, but recent calls to put the health of the council’s balance sheet ahead of the health of our planet and our children’s future are casting doubt over its viability.

The scheme has been unanimously backed by Councillors in Perth & Kinross. Councillor John Kellas summed up the mood when he said: “We in Perth and Kinross have an opportunity with this scheme to lead the field.” A sentiment shared by all of his fellow councillors.

The Scheme

Map showing River Tay Water Source Heat Pump and District Heating Network along with the Solar Farm location

The Perth City River Tay Heat Pump is an ambitious project that aims to show that water source heat pumps are a viable proposition, even in a river such as the Tay that is ecologically sensitive and is designated as a Special Area of Conservation. If successful, it will generate renewable energy that will supply heat to premises alongside the river, including Council Offices and residential properties, via a District Heating Network.

The proposal includes the possibility for natural gas to be used by auxiliary boilers so that the heat obtained from the river can be topped up when demand is very high, such as might be the case in the depths of winter. The scheme also includes thermal stores that will keep excess heat from the heat pumps when demand is low and allow this to be made available when needed later.

The scheme will provide affordable heat to many homes in Perth and allow technological expertise to be developed locally, which will boost the economy and allow us to export skills from the Perth area.

Speaking earlier this year after he and his colleagues at Perth and Kinross Council’s strategic policy & resources committee had given their backing to the £8.2 million pound project, Council leader Ian Miller said: “This is a hugely important paper. Investing in key infrastructure is one way that our council can support our residents, local economy and business sector.” Councillor Miller went on to say: “This report provides a really good example of how this council can be ambitious and innovative in addressing economic, social and environmental challenges. This scheme will boost local enterprise, reduce fuel poverty and reduce carbon emissions.”

According to Vice-convener Alan Grant, similar projects are already operating well in other countries in Europe, including Italy and Norway. A more detailed business case will be discussed by councillors at a future date.

Scottish Government has already awarded funding of £2 million from the Local Energy Challenge Fund and PKC will be looking into other funding sources to ensure all the money is available by the end of 2016. The expectation is that the loans will be repaid using money from the distribution of heat through what will be the largest project of this type in the UK and links with the 300 panel solar park in the north of Perth.

Background – Tay Eco Valley

The scheme was developed for a number of compelling reasons, including to meet the strategic aims of the Tay Eco-Valley, which are as follows.

  • To promote the Tay Eco Valley, which it is hoped will become a major focus of expertise and a hub for environmental innovation.
  • To generate discussion about novel solutions to the sustainability problem, and to serve as a fillip for environmental innovation and business growth.
  • To provide clear opportunities for supporting businesses to grow, for example finance, construction and so on.
  • To serve as a powerful demonstration of the opportunities that such projects offer for the growth of local businesses.
  • To increase collaboration between the public, private and community sectors on eco-innovation in the Eco-Valley area.
  • To help improve local skills and training to help deliver eco-innovation.

The Tay WSHP will help to meet the strategic aims of the eco valley in a number of ways. In particular, it will reduce carbon impacts from energy consumption and production, promote the development of clean technologies and serve to demonstrate environmental technologies.

The objectives of the WSHP scheme are as follows.

  • To use the water heat pumps as a source of renewable energy from the River Tay without damaging the sensitive ecology.
  • Create a district heating network to supply affordable heat to 4 business plots, 211 social housing and 2 Council buildings (a Daycare Home and a Primary School).
  • Installation of a solar farm that will generate electricity to be distributed via a private network.
  • Boost local enterprise, mitigate fuel poverty and reduce carbon dioxide emissions from heating.
  • Put Perth City on the map, as part of the Tay Eco-Valley as a UK and European leader in eco-innovation.
  • Provide a blueprint for other similar projects that can be used elsewhere.

Costs

The overall cost of the project is estimated at £8.2M and includes the cost of an energy centre and innovation hub, which will be housed on the Perth Food & Drink Park. The building will allow for the sharing of facilities such as back-office staff, conference rooms etc and will promote resource efficiency in the food and drink sector. The costs for the building will be around £4.5M.

The heat network itself will include 2.3km of pipework and associated infrastructure. The network will connect four plots incorporating 5 small business units and the Food and Drink Park, 211 houses and North Muirton Primary School. It is expected to cost £2.3M in total.

Other costs, relating to planning, project management, professional fees and contingency are likely to total £1.4M.

Part of the above costs will be met by the Local Energy Challenge Fund, which will go towards the heat pipe network.

Some figures taken from the heat and the city website:

  • 2MW Water Heat Pump to provide 4MWh heat load and cooling
  • 75Kwh solar farm (300 panels)
  • 3km pipe network
  • Total Solar Farm Costs: 95K funded from Commercial Property and Investment Programme generating income of around 10K per year over 20 years.
  • Total Energy Centre/Innovation Hub and network costs: £8.2m

The costs are being met, in part, by the successful bid placed by the Council for funding from the Local Energy Challenge Fund. The Local Energy Challenge Fund was set up in August 2014 to help promote local low carbon energy initiatives. Its chief aim is to help big, low carbon projects that can show strong local energy economy approaches linking local energy generation and use.

It is expected that the scheme will promote a busy and growing economy, helping businesses to reduce their carbon footprints, improve their green qualifications whilst bringing increased employment and real eco-innovation to the area. Jobs will be created on the Food and Drink Park and in the surrounding area through supporting businesses. Making available low-cost heat to homes and businesses in North Muirton and Muirton, the water source heat pump and district heat network will provide greater impetus to the local economy, lower fuel poverty rates and help to minimise carbon dioxide emissions from heating.

Benefits

The benefits of the scheme include reducing fuel poverty in a particularly deprived area of Scotland. This will be achieved through the expected reduction in bills brought about by the district heating network. The savings are expected to be of the order of £46,000 per year. It is expected that approximately £200/year will be saved by households currently using electricity to heat their homes and around £100/year for those using gas.

Carbon emissions will see a reduction of 450 tonnes per year of carbon dioxide.

Food and Drinks businesses will be brought to the Food & Drink Park where they can use the lower cost heat and electricity from the renewable energy systems. This will give them lower heating and electricity bills, improve their eco-friendly status and encourage resource efficiency in the Food and Drink Sector as a whole. All of this will be promoted using the innovation hub on the park.

Education benefits from involvement of local schools, such as North Muirton Primary School as part of the curriculum for excellence.

Speaking about the benefits of the scheme, Councillor Alan Grant, Vice-Convener of the Strategic Policy & Resources Committee, said: “The River Tay Heat Pump and District Heating Project allows us to tap into the immense power of the river in a way which will not harm wildlife, but will provide a source of renewable energy and access to cheaper heating to reduce fuel poverty in the north of Perth and help attract more food & drink related businesses to Perth on the basis of lower energy costs.”

He also went on to say: “The project will also be used as a model for the roll-out of similar schemes across the region, and potentially across Scotland. Together with the solar farm at Perth Food & Drink Park, this project demonstrates the exciting potential of Perth City as we continue to innovate for the future, and in doing so create higher-value, higher-skilled jobs.”

Delivery

The solar farm was scheduled to be finished in March 2016 and was the first part of the project to be built. It comprises 300 panels and has been built on a section of the Food and Drink Park that would be unfavourable for other types of development.

The combined earnings from the heat pump and electricity from the farm are expected to be around £10,000 per year for a period of 20 years. This will help to support the running costs of the park.

The Energy Centre and Innovation Hub and accompanying network should have finances in place by June 2017 and be operational by early 2018.

Future expansion plans include taking the network out towards Gowans Terrace and linking in Perth Grammar School, North Inch Campus, Caledonian Social Housing and other Council buildings. Eventually the scheme could be linked in with other schemes  in the area and would bring it to the same sort of scale as those already being run in Europe.

Once the project becomes well-known, it is expected that it will become a showpiece for the Tay Eco-Valley, which will in turn generate investment from outside the area.

Hopefully the difficulties over the project timescales slipping, and the likelihood that the important funding deadline in March 2018 will be missed, can be overcome. The council is expected to re-apply for the money in the next funding round. If that later bid is successful, we can all look forward to Perth and its surrounding area not only becoming that little bit greener, but also leading the high-tech revolution that is being driven by the need to innovate to meet our climate change targets in 2020.

The River Tay Heat Pump and District Heating project is a large scale ambitious project. However, smaller scale examples exist at the domestic level, such as described in the case study here.