Illustration of ground-source heat pump

Eco heating: what are the options?

Are electric radiators green? Mike Childs, Head of Science, Policy and Research at Friends of the Earth, reviews the pros and cons of everything from storage heaters to biomass boilers to heat pumps and more.
Picture of Mike Childs
By Mike Childs    |      Published:  11 Oct 2018    |      Last updated:  17 Jan 2019    |      10 minute read

Until recently I had one big carbon footprint secret that significantly diminished my green credentials: all the hot water and heating in my home was contributing to climate breakdown. But after weighing the pros and cons of potential solutions, I’ve now got a new low carbon heating system.

Your gas or oil boiler – which will also run your radiators – may also be undoing your attempts to slash your climate-wrecking emissions. Over 90% of homes in the UK are heated in this way.

Take my terraced house with its well-insulated loft. When it had a modern gas-fired boiler it produced around 2.75 tonnes of planet-warming greenhouse gases a year – the same amount as driving 11,770 miles in an average car, or flying 11 round trips to and from Rome.

So if you’re lucky enough to be a homeowner, and you want to cut your home’s carbon footprint, what are your options?

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Insulation 

Starting with insulation is the best bet. You can pay about £50 for an energy performance assessor to identify the insulation options suitable for your home (the government has a list of accredited assessors). And Energy Savings Trust produces independent advice on your options.

I’ve done a lot of insulation on my house. Good quality windows and doors have made a big difference. But with solid walls (i.e those that don’t contain cavity walls) heat still pours out. The house is small and I didn’t want to lose any more space through internal wall insulation. Living mid-terrace made external-wall insulation impractical. So I resorted to 1 cm-thick thermal wallpaper which certainly made a difference to our comfort levels. This is an area currently attracting a lot of innovative solutions, such as insulating paints and high-tech plaster.

illustration of thermal wallpaper and paint
Credit: Russell Hardman/Friends of the Earth

When it comes to paying for insulation, the government obliges energy companies to help householders fit insulation under a scheme called the Energy Company Obligation. Money for this has been cut in recent years and the programme is now targeted at low income and vulnerable households, but there are still government-led grants available in Wales, Northern Ireland and Scotland.

Pros: Insulation will cut energy bills, but big investments such as high-quality windows, doors, or external-wall insulation will take many years to pay back – decades in some cases. If you can afford it, the added comfort is worth it in my view.

Cons: Apart from the upfront cost, the biggest obstacle is disruption and mess. One way of minimising this for internal-wall insulation is to do it room by room when decorating.

illustration of smart heating controls - remote, radiator and wall theremostat
Credit: Russell Hardman/Friends of the Earth

Smart controls

Smart heating controls enable you to easily manage your heating. You can even do it from your phone or computer when you're away from home. Smart controls can automatically adjust the heating according to the weather and to whether or not you're at home.

study on the NEST smart heating controller suggested a minimum saving of around 5% in gas consumption, even for homes that already have heating controls such as radiator valves and a programmer. You can also get individual room controls, which would save more energy.

These should all, in theory, pay for themselves within around 5 years, and the cost range is about £200-250.

Make sure you read up-to-date reviews of different smart heating control options, as there's currently a lot of innovation in this area: it's a fast-moving and competitive market with new options emerging all the time.

Pros: Smart heating controls will pay back fast (within 5 years).

Cons: Can't think of any.

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Exploring different heating options 

There is a range of options for home heating and they all have pros and cons. Some are more suitable for some homes than others. Annoyingly the choice isn’t straightforward.

Heat pumps 

A heat pump is basically the same as a fridge in reverse. Rather than making the inside colder and transferring the heat outside it does the opposite – it extracts heat from the environment outside the house and pumps it into the house. Roughly speaking, for every unit of electricity you use, it will provide 3 units of heat. It's therefore by far the most efficient form of heating there is.

Remarkably it does this even when it’s freezing outside – in fact, heat pumps are now the most fitted heating device in chilly Sweden.

There are 4 types of heat pump:

Hybrid heat pump works alongside your gas boiler. Smart controls pioneered by UK company PassivSystems enable you to maximise your carbon pollution savings (although currently their controls only work with a few brands). The controls do this by switching between the heat pump and gas boiler to use whichever is lowest carbon at the time. So, when electricity from the grid is low carbon the heat pump is used to provide your heat. When the electricity grid is being powered with lots of fossil fuels, the gas boiler will be cleaner and the controls switch to that. On really cold days the controls can use both simultaneously to keep your home nice and warm.

Air-source heat pump extracts heat from the air outside (even when it’s cold!) and uses it to heat the water in your radiators and in your hot water tank if you have one. The heat pump needs to be outside your property. It doesn’t make the water as hot as a gas-fired boiler, so to ensure your house is warm enough it runs for longer. You're also likely to need to increase the size of your radiators. The fan in the heat pump (which also needs to be outside the house) will make some noise, but no more than the background hum of a fridge. Of course the pump will be busiest during the winter months when you are less likely to be outside anyway. This is the option I plumped for.

Ground-source heat pump extracts heat from the ground, so requires a garden for a trench. It is more expensive than an air-source heat pump, but also more efficient and quieter.

Air-air heat pump blows warm air into your house rather than hot water. If you have multiple floors to heat you will need more than one of these.

Illustration of ground-source heat pump
Credit: Russell Hardman/Friends of the Earth

Costs of heat pumps

Heat pumps will give you an impressive 50-60% reduction in your greenhouse gas pollution footprint, and they shouldn’t increase your energy bill. In fact, if you live in an off-grid property currently powered by oil or LNG (Liquefied Natural Gas) and you switch to a heat pump, the greenhouse gas pollution saving will be greater because oil and LNG are particularly polluting fuels. You can also use smart controls and the variable energy charges pioneered by Octopus Energy to use the heat pump when energy costs are lower during the day./p>

But they do come with an upfront cost, including installation. The following are (as yet) unpublished estimates provided to the government by consultancy Delta-EE: around £12,500 for an air-source heat pump, £23,000 for a ground-source heat pump, and £16,500 for an air-air heat pump. The consultancy company weren’t asked for the price of a hybrid heat pump, although it is likely to be similar to an air-source heat pump. These figures are estimates, and the actual price will depend on your home. The cost of my air-source heat pump was £11, 392.50, which included fitting a hot water tank for baths, showers etc.

A government grant is available to cover some of the cost, though not for air-air heat pumps. The amount of grant will vary by technology and how efficiently it will operate in your home, but is likely to cover at least half the cost. In my case, around half the cost will be covered by a grant, which is paid quarterly over the next 7 years. You need to use an accredited installer to get the grant – they’ll be able to give you an estimate once they've inspected your property.

Pros: Heat pumps are a very efficient way of providing heating, using roughly 1 unit of electricity to produce 3 units of heat; they are also eligible for a government grant.

Cons: Heat pumps do involve some disruption to your house, eg pipework, and some systems will need bigger radiators. You'll need to be happy with a heat pump outside your house making some noise, although it’s only about as loud as a fridge, and will be working hardest in winter when you are less likely to be outside.

Heat batteries

New on the scene are heat batteries, which can store the heat produced by your heat pump for later use. The heat can then be used to provide instant hot water for showers and baths, as well as heat your radiators.  This approach means you can use your heat pump when the price or carbon intensity of electricity is low - often during the middle of the night - and use heat when you most need it (e.g. first thing in the morning or the evening). They also do away with the need for a hot water tank.

As well as working with heat pumps, they can also be used with solar thermal panels, solar PV panels, or charged directly by electricity. They are also small – about a third of the size of a hot water tank and small enough to fit in a standard kitchen cabinet.

Pros: Heat batteries are compact, much better at storing heat than a hot water tank and therefore more efficient, and they enable you to use low cost electricity.

Cons: The upfront cost of installation is likely to be higher than fitting a hot water tank, but they will reduce running costs by 30-40%  by using off-peak low-cost electricity and reducing heat losses, so will save money over time.

High-heat retention storage heaters 

These are much better insulated than the old fashioned storage heaters. This means they're much better at providing the heat when you need it, while enabling you to use the cheaper economy 7 energy tariffs or the Octopus Agile tariff. Economy 7 tariffs are available at the times when the electricity grid has less dirty fossil fuels feeding it – so it comes with a lower carbon pollution footprint.

The switch to high-heat storage heaters is straightforward, so long as you have an electric supply near to where you want to fit the radiators. They come with individual room controls and the better models match energy input to weather conditions. However, we have not found an independent review of the different models.

Currently high-heat retention storage heaters won’t reduce your greenhouse gas pollution compared to your gas boiler (especially if you already have smart heating controls). But in a few years’ time they will, as the electricity grid gets more power from renewables, so if you need to replace your boiler it’s worth opting for these (if you don’t want a heat-pump).

Caveat: they will cost you more to run, because even economy 7 electricity is more expensive than gas. The additional cost is likely to be around 20% more according to our calculations.

High-heat retention storage heaters don’t heat your water. If you have the roof space, solar thermal panels can help you with that, and government grants are available (for thermal panels) under the Renewable Heat Incentive. You will need to use an accredited installer to get the grant, which should cover at least half the cost of around £5,000. High-heat retention storage units are a lot cheaper than heat pumps to fit though, costing around £7,000 if you have 8 radiators.

Pros: Cheaper than heat pumps to fit. Easy to install. In a few years' time they will reduce your carbon footprint.

Cons: No government grants available for high-heat retention storage heaters.

Illustration of domestic heating radiator
Credit: Russell Hardman/Friends of the Earth

Electric radiators 

These radiators use electricity to provide you with heat when you need it. They are cheap to buy and fit compared to the options above. They might cost less than a new gas-fired boiler. Many will be programmable and have smart controls.

However, they will cost you an arm and leg to run – potentially tripling your energy bill.

For at least the next 5 years (and probably longer) they will generate more greenhouse gas pollution than your gas-fired boiler. This is partly because they use electricity at peak times, when the grid is mostly powered by fossil fuels.

If you're concerned about the environment you won’t want to opt for electric radiators. And beware the sales people: we've seen a number of eyebrow-raising claims.

Pros: None that I can think of. 

Cons: Will increase your carbon footprint for at least the next 5 years.  

Infrared heaters 

Infrared heaters are pretty new to the market They provide warmth by heating objects rather than the air – like sitting in the sun on a winter’s day, you can still feel warm even though the air is cold around you. That doesn’t mean your house will be cold, because as your household belongings and the fabric of the house (such as sofas, floors, walls, etc) warm up, they will radiate the heat back out.

One company selling these heaters (Herschel Infrared) gave us illustrations that suggested heating bills will reduce by around a third compared to conventional electric radiators. If this is true, they will out-perform electric radiators in both costs and carbon footprint, although they still wouldn't be as good as heat pumps for reducing your carbon footprint.

One advantage of these heaters is that they are super thin and light-weight – they can be located on your ceilings pointing down, printed over to appear to be pictures on your wall, or hidden behind mirrors.

The retailers claim they will be no more expensive than fitting traditional electric heaters.

Pros: Can look great, and offer savings compared to conventional electric radiators, according to the manufacturers.

Cons: Because infrared heaters are new on the market there is little or no independent evidence on how well they work in practice. Like conventional electric radiators they will use peak time electricity, not Economy 7, so are likely to be more expensive to run than storage heaters and will increase your carbon footprint for at least a few more years.

Biomass boilers and stoves 

Biomass boilers have had financial support from the government under the Renewable Heat Incentive. At first glance they seem like a great option: what could be better than burning trees that can be replanted and managed sustainably? In reality, it's less clear cut than that (excuse the pun).

The carbon footprint of a biomass boiler or wood-burning stove depends very much on the source of the wood. So, unsurprisingly, we haven’t been able to calculate the carbon footprint of it. In many cases, it is likely to be worse for the climate than gas-fired heating systems. In urban areas wood burning is coming under the spotlight because of its contribution to air pollution (the intensity of which will vary enormously between models of stoves and burners).

For these reasons we haven’t looked in detail at biomass boilers and stoves. 

Make a choice 

Opting for a heat pump, or a hybrid heat pump, is the best option if you have outside space. In our well insulated pre-1900 house we've fitted an air-source heat pump and a hot water cylinder (although in hindsight I wish we’d fitted a heat battery instead). For a more modern house an air-source heat pump would also be perfect. In less well insulated homes a hybrid heat pump with smart controls would be the best bet.

If you don't want a heat pump, then a heat battery or high-heat retention storage heaters aren’t a bad fallback – their ability to deliver carbon footprint reductions will increase in line with an increase in renewable energy on the grid.

Whatever your choice, insulation is always going to be the best first move.

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Resources

  • Cost and carbon footprint illustrations for a number of options for reducing the carbon footprint from home heating: Greener home heating [PDF document].

  • Our volunteer Chris has produced a fantastic calculator that brings together official data on costs, carbon impact, housing types and grants; you'll need to be comfortable with spreadsheets to use and understand it. If you'd like us to send you a copy please contact us.