Boilers

Finding an ethical and eco-friendly boiler

From a climate perspective, heating is an urgent thing for consumers to address. It accounts for around 14% of the UK's greenhouse gas emissions if you count them territorially, or 9% including imports. And it has to be addressed at home, as that’s where the burning happens.

The UK is doing very badly at decarbonising heating. Houses in the UK are poorly insulated, and we are addicted to gas boilers.

Even if you’re not about to buy a boiler, this guide is still for you. If you find new ways to streamline your hot water requirements, adjust some boiler settings (and get your boiler serviced), you could cut costs and emissions right now.

Are there any environmentally-friendly boilers?

None of the brands in this guide receive our 'best buy' rating, and there's only four points between the top and bottom scoring brands. The finer details like price and warranties may help you differentiate between brands. We cover both topics in this guide.

If you are about to buy a boiler, we recommend that you don’t. A heat pump is much better for the climate if it’s possible for you. However, we realise that heat pumps are out of many people’s price range, so we are covering boilers again. This guide covers both gas and electric boilers.

There is a UK ban on fitting gas (and oil) boilers to new homes from 2025, with phase-outs for replacement boilers also expected, in order to wean ourselves off gas and cut carbon emissions.

Electric boilers v gas boilers

Electric boilers are not the best alternative for home heating. They are much more expensive to run than a gas boiler (because the price of electricity is higher than gas) and won’t currently save you carbon, although over their likely 15-year lifetime, the grid will hopefully decarbonise more and so that may change.

But even if it does, they would not be suitable for everyone as it would raise electricity demand too much on cold winter evenings when we all turn our heating up at once.

Electric heat pumps are several times more efficient at converting electricity to heat, and are the solution being proposed by the expert organisations. Our guide to heat pumps has more information.

Are electric boilers more energy efficient?

The ErP (Energy related Product) labelling of products for energy efficiency runs from G (likely rating for a non-condensing gas boiler which is under 70% efficient, pre-2005) to A (applies to all modern condensing gas boilers, which have the potential to be over 90% efficient.)

The label also lists the boiler's output (or 'size') in kW.

Although electric boilers are more efficient (up to 100%) than gas boilers at the point of use, confusingly, they have lower ErP ratings. This is for several reasons: the inefficiency and higher greenhouse gas emissions of UK electricity production at source, while it is still (about 40%) reliant on burning fossil fuels, and, the price of electricity.

Some campaigners argue that gas boilers ErP ratings should also be revised down for relying on fossil fuels, in order to better promote lower carbon products.

Looking ahead, about 40% of UK electricity production is already powered by renewables, and the National Grid is hoping wind and solar output will increase five-fold by 2030.

Can you make your boiler more efficient?

The efficiency percentage, which is not listed on the label, relates to how much of the energy used by the boiler actually heats the home, rather than just keeps the boiler running. However, a boiler will only reach its efficiency potential if it’s installed to do so, and many engineers have not been trained to do this.

Our energy savings tips further down in this guide suggest how you can change some settings yourself. A heating engineer could also adjust the ‘size’ of your boiler so that it is running on a lower ‘minimum output’ and condensing more efficiently.

How much does a boiler cost?

Boilers vary a lot in how much they cost to buy, install and run depending on a number of factors such as model, dimensions, efficiency, power, and controls.

All prices listed are excluding cost of installation and are indicative, according to what was found in January 2023.

According to the Boilers Prices website, the average installation cost of having a new boiler fitted in the UK is around £1,500–£1,800. In terms of cost and complexity, gas boilers are generally more complicated to install compared to electric boilers.

Cost of running will depend on the size (its energy output in KW, rather than physical size) of the boiler, its efficiency rating, how many hours it’s in use per day and the number of radiators a person has in their home.

The only company that discussed the running costs of its products on its website was Thermaflow. Thermaflow’s website includes a useful summary of average annual running costs for its different electric boiler models, with costs ranging from around £1,000 to £2,000, depending on the volume and kW of the boiler, whether it was for 1-to-4-bedroom properties, and with the assumption that its use was for only two people.

Are second-hand boilers worth it?

As the advice on a boiler trade website puts it:

“Not many people upgrade their boiler when it is working perfectly, and this means finding a working combi boiler in good condition is a rarity. Also, how do you check your second-hand boiler is working properly before it is fitted?”

Newer boilers are also more energy efficient. So, although it might seem like an environment-saving action to buy a second-hand boiler, overall, that’s likely not to be the case once it’s installed and running.

Older used boilers may also not have easily available parts if they need repairing, as the manufacturer may have stopped producing parts for older models. It’s also unlikely that an older used boiler will still have its warranty.

A potential way to save on the cost of buying a new boiler is to approach a boiler or plumbing company and buy one of its ‘old’ display models in its shop.

Warranties for boilers

There is not much to separate the companies in this guide in terms of their Ethiscores, but when we looked at the warranties we found quite a large variation. So, it’s worth checking the terms and conditions, and how soon after acquiring a boiler you have to register it to receive cover (we found this was usually within 30 days).

Length of warranty ranged from one to twelve years, depending on who installed the boiler, if/when it was registered, and the model of boiler.

Electric boiler warranties tend to be shorter but they are less likely to have faults and it’s not as important to service them annually, compared to gas boilers.

The table below shows the warranty periods we found according to the brands’ terms and conditions if the boiler was registered.

Most brands had cover for both labour and parts, but some did not offer both for the duration of the warranty length (e.g. Electric Heating Company, Thermaflow). Some terms and conditions stated that a filter should be fitted, or an annual service should be carried out for the warranty to be valid.

A lot of the longer warranties were only available if an installer from the company selling the boiler fitted and registered it.

*Worcester Bosch did not offer a warranty but a guarantee, with a checker on its website.

Service your boiler

According to a Which? survey, around three in ten boilers that are serviced annually needed a repair in their first six years. This doubled to around six in ten boilers if the boiler was only serviced every two to five years.

They also found that paying for repairs only when needed was cheaper than paying through a boiler cover scheme. You might already have cover for boiler breakdown if you have home insurance, so check that too.

For servicing, Which? recommends a list of trusted traders, who are all Gas Safe-registered engineers, and it should cost about £86, as of January 2023. If you need reminders, you can get an app called Benchmark.

Are there any eco friendly boiler brands?

For this research we looked at what brands were doing about their carbon emissions and environmental reporting.

Discussions of reducing carbon impacts have improved overall since we last rated boilers but Vaillant, Bosch and BDR Thermea (Baxi, Heatrae Sadia, Main, Potterton) are still not calculating the carbon impact of their supply chains and the use of their products, which are known as Scope 3 emissions.

Groupe Atlantic (Ideal, Keston) is not even reporting the emissions of its own operations yet.

Viessmann was the only company with full reporting of its emissions and a credible reduction target. It talked about the investment it had made in powering its own operations with solar, heat pumps and green gases. However, it was marked down for owning a commercial airport and planes.

The electric boiler companies were generally proud of their focus on alternatives to gas boilers, and exploring lower-carbon tech. But none had any information on reducing their own impacts, either in terms of carbon or other environmental issues like water, waste, or materials – other than Elnur, which said it was producing its own energy to power 86% of its production processes.

In terms of other environmental issues, we found discussion of reducing water consumption (Vaillant, Bosch), waste (Groupe Atlantic, Viessmann, Bosch), and material usage (Viessmann, Bosch).

What are boiler companies doing about toxic substances in electronics?

Both gas and electric boilers have electrical components in them, so we scored companies for their policies on toxic substances used in electronic equipment.

All of the companies scored a worst for their lack of any publicly available policies on hazardous materials.

Change your boiler setting to save energy and money

In October 2022, the Money Saving Boiler Challenge was launched by Nesta, a UK charity that promotes innovation. They want at least one million households to change their combi boiler settings this winter to save energy.

It turns out that many boilers are installed to have a ‘flow temperature’ of 70-80°C but could be turned down to 60°C or even lower, using less gas and thereby saving emissions and money.

This is nothing to do with your thermostat and doesn’t mean your radiators won’t get as hot. It’ll just take a little longer than before, and the boiler will be able to condense more efficiently, recovering more heat as it’s designed to do. If your flow temperature was on 80 degrees to start with this could knock over £100 off your household’s annual energy bill and save you 170 kg of carbon emissions (which is about 1% of your total carbon footprint). And it only takes a few minutes to make the change.

Nesta also explains more ways that don’t cost anything to save gas at home, including lowering the settings on radiators, turning down the hot water temperature, and reducing the cylinder temperature safely if you don’t have a combi boiler – boilers with a hot water tank need to be kept over 60°C to avoid Legionnaires disease.

What are boiler companies doing about workers’ rights?

All of the companies we rated scored a worst for supply chain management and human rights.

None of the electric boiler companies had any publicly available information on their supply chain policies.

For gas boilers, none of the companies had policies on providing a living wage, and while all of the companies said they prohibited child labour, only BDR Thermea (Baxi, Main, Potterton, Heatrae Sadia) and Robert Bosch (Worcester Bosch) defined the age of a child.

Only BDR Thermea and Vaillant (including Glow-worm) had a complaints system where supply chain workers could make a complaint anonymously and free of charge in their chosen language.

Are any boiler companies avoiding tax?

Viessmann and Worcester Bosch scored worst for tax conduct, as both companies were found to have dubious company structures with high-risk company types registered in countries considered by Ethical Consumer to be tax havens.

Groupe Atlantic (Ideal, Keston) scored middle as its family tree was slightly less risky.

Alternative to gas boilers

Hydrogen boilers are a diversion

In September 2022, the campaign organisation Global Witness released a report criticising several gas boiler companies for their misleading messaging around hydrogen boilers:

"Gas boiler companies are greenwashing their products with hydrogen- or hydrogen-blend ready labels, making them appear climate friendly."

All of the gas boiler manufacturers in this guide are members of the industry body EHI (European Heating Industry), which has lobbied for the EU to promote hydrogen-ready appliances, as well as phasing hydrogen into the gas system.

Bosch, Baxi (BDR Thermea) and Vaillant (Glow-worm, Vaillant) have all been saying “The only by-product of burning hydrogen gas is water”, while Viessmann said hydrogen is “emission-free”. However, when it is burned in air, rather than pure oxygen, it produces dangerous nitrogen oxides which exacerbate respiratory problems.

It’s true that burning hydrogen does not produce carbon emissions, but unfortunately, 96% of Europe’s hydrogen is currently produced by burning fossil fuels. There are also concerns about hydrogen leaks, as it reacts with other gases in the atmosphere, giving it a warming potential 33 times greater than carbon dioxide over a twenty-year period.

Hydrogen and cost

There are also big concerns around affordability. Global Witness referred to several studies which found heating with hydrogen boilers to cost more than heat pumps over their lifespan, even though heat pumps cost more to buy up front.

A separate review of 32 hydrogen studies, published in the peer-reviewed journal Joule, concluded that “hydrogen use for domestic heating is less economic, less efficient, more resource intensive” than several low- and no-carbon alternatives, and “associated with larger environmental impacts.”

A range of international and national bodies say that hydrogen fuel should be reserved for sectors where more efficient and cheaper technologies do not exist, i.e., not for home heating. Tempting people to buy ‘hydrogen-ready’ boilers, when no-one even knows if hydrogen will be used in this way, could distract people from the real alternatives and keep them on the grid.

The Global Witness report concludes that:

"Boiler manufacturers appear to be cynically and misleadingly marketing hydrogen-ready boilers, taking advantage of customers’ desire to take climate action, to allow themselves to continue to sell fossil gas boilers and avoid changes to their business models."

The Climate Change Committee – the statutory body that advises our government on decarbonisation – agrees that hydrogen is unlikely to be cheaper than heat pumps when you take everything into account. Its decarbonisation scenarios include only small amounts of hydrogen for heating, in combination with hybrid heat pumps.

What about biomass boilers?

Like hydrogen, the limited supply of biomass is generally agreed to be best used for other sectors where better low-carbon alternatives don’t already exist. For more information see the heating section of our Climate Gap report.

Additional research for the guide by Louisa Gould.