Illustration of ground-source heat pump

Eco heating: what are the options?

Are electric radiators green? The pros and cons of everything from storage heaters to biomass boilers and more. What's hot and what's not.
By Mike Childs    |      11 Oct 2018    |      16 min

I like to think I'm pretty green. But I’ve got one big carbon footprint secret. All the hot water and heating in my home is contributing to climate change.

Yes, your hot water heater – which might also run your radiators – could be furtively undoing your attempts to slash your climate-wrecking emissions.

Take my Victorian mid-terrace house with a well-insulated loft and a modern gas-fired boiler. Heating it produces 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.

Right now, heating my home is very polluting. And I’m determined to fix it. So what are the options?


Starting with insulation is invariably 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 the 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 it still pours out heat. 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 comfort. This is as an area with a lot of innovation right now, such as insulating paints and high-tech plaster.

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

In terms of 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 also 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. But 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
Credit: Russell Hardman/Friends of the Earth

Smart controls

My next investment will be smart heating controls. These 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.

A 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.

Here’s a good review of different smart heating control options. There's a lot of innovation in this area right now. 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.

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.

Essentially a heat pump extracts heat from the environment outside the house and pumps it into the house. Roughly 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 3 types of heat pump:

Air-source heat pump – this extracts heat from the air outside 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; and you're also likely to need to increase the size of your radiators. The fan in the heat pump will make some noise, about the level of a quiet conversation from a meter away. Of course the pump will be busiest during the winter months when you are less likely to be outside anyway.

Ground-source heat pump – this 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 pumps – this 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.

Hybrid heat pumps – these work alongside your gas boiler, which kicks in when the temperature outside plummets. For some older houses that can’t reach high insulation standards these pumps might be ideal, providing heating 80-90% of the time with gas powering the heating in those increasingly rare cold snaps. Hybrid heat pumps don’t require radiators to be replaced, which reduces the price by a bit (although you’d need to keep a gas boiler).

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.

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. (They were not asked for a price of a hybrid heat pump, although it is likely to be similar to an air-source heat pump.) The actual price will depend on your home. The costs given are central costs within a range.

A government grant is available to cover some of the cost, though not for air-air heat pumps - which aren't eligible. 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 and maybe much more. You need to use an accredited installer to get the grant. They will be able to give you an accurate figure 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 gas boiler, and will be working hardest in winter when you are less likely to be outside.

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. 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 as 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.

Right now 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.

However, 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 units are a lot cheaper than heat pumps to fit though, costing around £7,000 if you have 8 radiators.

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 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.

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

Cons: No government grants available.

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

Electric radiators

These are radiators that use electricity to provide you with the 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.

But 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 has most fossil fuels powering it.

Interestingly, if fracking takes off in a big way in England, the gas burning in your gas-fired boiler will get a lot dirtier, potentially making the electric radiator option more attractive. However, with your support we're confident we can defeat fracking, so I’ll discount this from the equation for this exercise.

If you're environmentally-minded 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

Pretty new to the market are far infrared heaters. These 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 (eg 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 and storage heaters 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 are that they are super thin and light-weight, so 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 big savings compared to other electric heaters, according to the manufacturers.

Cons: Because these are new on the market there is little or no independent evidence on how well they work in practice.

Biomass boilers and stoves

Biomass boilers have had financial support from the government under its Renewable Heat Incentive. At first glance they seem like a great option: after all what can be better than burning trees that can be replanted and managed sustainably? Actually, 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, not surprisingly, we haven’t been able to model it. In many cases, perhaps even the majority, 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 quantity of air pollution will vary enormously between models of stoves and burners.

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

Future options

There is a hot debate in policy circles about whether we should replace natural gas in the grid with hydrogen. Hydrogen can be produced from renewable energy using a technology called electrolysis. This would require gas appliances such as boilers, cooker and fires to be changed in all homes. This scale of change has happened before – when the UK switched from town gas to natural gas over 1968-76. But it's likely to be 10 years or more, if ever, before such a switch to hydrogen. And if it did happen the fuel will cost more than natural gas.

If this happens, simply replacing your current boiler with a hydrogen boiler will be a green option, as long as the hydrogen is made from renewable power.

Alternatively, you might want to install a fuel-cell combined heat and power (CHP) system. These work by chemically converting the energy in gas to both heat and electricity; you would still need a boiler for colder periods to boost the heating. CHP could in theory be used right now, as it can use natural gas as well as hydrogen. However, in much of the UK CHP will only reduce your carbon footprint by a fraction at best because home-generating your electricity from natural gas is no less polluting than buying electricity from the grid. In Northern Ireland, which still uses a lot of coal-fired power, fuel-cell CHP is a good bet right now, albeit very expensive.

Make a choice

Opting for a heat pump, or a hybrid heat pump, is probably the best option right now if you have outside space.

I don’t have much space outside, and fitting a heat pump would mean my partner and I thinking long and hard about how much we can spare our miniscule garden.

Infrared heaters or high-heat retention storage heaters aren’t a bad fallback. They will increasingly deliver carbon footprint reductions as electricity in the grid comes more from renewable energy. That is with the exception of Northern Ireland, where infrared and storage heaters will be worse for the climate for some time because the carbon footprint of electricity there. An independent review of the different models of high-heat retention storage heaters would be helpful.

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


  • 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.