Our Sustainable Homes Advice Service team have put together answers to some frequently asked questions to help you if you're considering making the transition to low carbon energy or already have a heat pump.
What types of heat pump are there?
A heat pump draws heat from a renewing source and, using a similar technology to a refrigerator, putting it into a system that distributes heat through your home. (See our Simple Guides for more information about using heat pumps.)
An Air Source heat pump will take heat from the air outside your house and use this to warm water in a central heating system to heat radiators It will also produce hot water for your hot water cylinder.
An Air-to-Air heat pump takes heat from the air outside your house in the same way, but instead of using radiators, fan units called cassettes are used to blow warmed air around your house Some air-to-air heating systems can also provide cooling (working in reverse as an air conditioner) and can dehumidify your house as well. An air-to-air heat pump does not provide hot water, so an immersion heater in a hot water cylinder is also needed.
A Ground Source heat pump takes heat from the ground, either using a vertical borehole or trenches with a long pipe that has a liquid in it that draws heat from the surrounding ground. The heat pump then puts this heat into radiators in a central heating system and hot water in a hot water cylinder.
If you are fortunate to live close to a river or even the sea, a Water Source heat pump can be used in the same way to draw heat from water. Due to the technical challenges of this set-up, water-sourced heat pumps are not common, but the technology for using the heat is the same.
Does a heat pump work when it's freezing outside?
Heat pumps can work in temperatures as low as -15°C. In fact, Finland has the highest rate of heat pump installs in Europe, despite being one of the coldest countries
Air source heat pumps must work harder when the air is colder but will be able to manage a frosty morning; the winter climate in Cornwall is quite suitable for a heat pump. The outdoor temperature does not affect ground source heat pumps because the ground temperature 1-2 metres down remains constant all year round
Can I use solar panels and a battery to power a heat pump?
Heat pumps can make use of solar electricity generated on-site, but most households using the power from a solar PV system will not make a big difference to heating bills. This is because a typical solar installation generates less energy than most houses will need to heat them over the course of a full year; additionally, most of this electricity is generated in the warmer months of the year when no heating is needed Adding a battery to a solar system will not make much difference to this situation.
Solar panels can be more effective at heating hot water by using a solar diverter or programming the heat pump to heat the water more in the daytime. Solar diverters switch excess solar generation into the immersion heater in the hot water cylinder and can often supply up to 50% of the annual hot water requirements
Do I need to insulate my house for a heat pump to work properly?
If you live in an uninsulated house, then you might find that a heat pump struggles to keep your house warm, or it is very expensive to run. Heat pumps work best in insulated houses because the pumps distribute heat at a lower temperature compared to a fossil fuel or electric heating system, and so good insulation levels will reduce heat losses.
Do I need underfloor heating?
Heat pumps work perfectly well with radiators, so underfloor heating is not required. However, heat pumps are more efficient with underfloor heating because the system will work at a lower temperature, about 35°C, to avoid burning people’s feet Underfloor heating is more expensive to install than radiators, and the property needs to be very well insulated or the lower heating temperatures will not be able to provide adequate heating into your main living spaces.
I already have central heating - do I need to replace all my radiators?
An installer should check if your existing radiators and pipework are suitable for a heat pump. They will outline which radiators need upgrading, usually replacing them with larger radiators, and if the pipework will need to be changed. Microbore central heating systems do not work with heat pumps and so a full system upgrade is required
Need more advice or help - call us on 0800 954 1956
Are heat pumps expensive to run?
Currently, heat pumps typically cost a bit more to run than fossil fuel heating systems, especially mains gas; they typically cost less than half as much as electric heating (night storage or panel heaters).
Why is my heat pump costing so much to run?
Some people contact us because they think their heat pump is costing them too much to run, or because they don't think it's heating their home properly
There could be many explanations for high electricity costs that are not related to the heat pump.
You are welcome to call us to review what is happening; we can check how your heat pump is set up and look at your other energy consumption to help identify what the issue is and what steps will help bring your costs down.
How much does a heat pump cost to install?
Installation costs vary because the set-up and requirements of every house is different. However, government figures from the Boiler Upgrade Scheme grant show that air source heat pumps typically cost between £11,000 and £15,000 to install (before any grants are applied)
Ground source heat pumps typically cost
between £18,500 and £36,000 to install (before any grants are applied) – the higher cost is due to the ground works for the pipework that supplies heat to the heat exchanger unit.
Air-to-air heat pumps are typically about half the cost of air source heat pumps that supply a central heating system, to install. Their running costs can be the lowest of all the heat pump types and they can be more effective at heating less well-insulated buildings. The fluids that move the heat to the cassettes which heat and blow warm air around, are regulated under the F-Gas rules, so you need to speak with an F-Gas accredited installer about quotations. Because they are classed as a type of air-conditioning, as the technology is commonly used, there is currently no government funding available for them
What carbon emissions do heat pumps produce?
Heat pumps are the best form of heating to use in terms of reducing carbon dioxide emissions; they produce several units of heat for every unit of electricity used to power them. Aside from the emissions generated in manufacturing new systems, the carbon emissions from operating a heat pump will continue to drop as we see an increase in the proportion of renewable energy which is used to supply the UK’s electricity network, and the amount of fossil fuelled generation used is reduced.
Are heat pumps noisy?
Air source heat pumps use a fan to blow air through the outside unit which causes some noise. A noise assessment will be included as part of the pre-installation survey, to ensure that operating noise levels are not breached in nearby bedrooms and living areas in your and your neighbours’ properties
Ground source heat pumps do not use a fan and are usually placed in a utility room away from living areas and do not produce any more noise than a fossil fuel boiler.
How much space does an air source heat pump need?
External
The outdoor unit generally requires a clear area with a solid foundation approximately 1m by 1.5m, with up to 1.5m clearance around the unit. There needs to be several metres of unobstructed space around the heat pump to allow enough air flow, to ensure that cold air does not get recirculated through the heat pump Small yard areas at the back of buildings are not recommended for these heat pumps; however, as with air conditioning units, an air source heat pump does not have to be situated on the ground but can be raised and affixed to a wall above head height if this provides better air flow.
An installer will carry out a survey to check there is enough room to install a heat pump
Internal
Heat pumps require a hot water cylinder, a smaller expansion cylinder and the associated pipework, so you will need space in your house to install these. The hot water cylinder is typically larger than a fossil fuel heated cylinder and the expansion vessel will need space, but they are designed to be retrofitted in place of existing cylinders (usually in an airing cupboard). In some cases, space for an additional buffer cylinder will be required, but these are only needed in specific circumstances. If you are replacing a gas combination boiler that has provided an instantaneous hot water supply, you will need to think about the best place to locate a hot water cylinder and expansion vessel
