How our boiler challenge is helping households save

Madeleine Gabriel, Mission Director in Nesta’s sustainable future team, discusses its money-saving boiler challenge and how it can help households this winter.

In the UK, the residential sector is the third-largest producer of greenhouse gas emissions, after transport and business. Homes are directly responsible for creating around 70 million tonnes of CO2 annually. Changing the way we heat our homes is one of the most impactful things we can do as a country to cut pollution. At the same time, with the ongoing cost of living crisis and a winter of energy bills to get through, finding ways to save households money and energy is front of mind for many advice giving organisations.

Our sustainable future team works on numerous projects at any one time – and one of these projects, way back in 2021, started to investigate the issue of boiler flow temperatures. The findings resulted in a national campaign that helped save an estimated 500,000 tonnes in CO2 and nearly £300m in savings for households,

What is boiler flow and why does it matter?

The flow temperature is the temperature that a boiler heats water up to before it goes around the radiators in your home.

Most combi boilers are set up with a flow temperature of 70C-80C – but actually, at 60 degrees the boiler is better able to condense, so it’s more energy efficient for the flow temperature to be lower. We wanted to understand what the impact of lowering the flow temperature would be on household gas use, to see how we could save energy.

Our research was rooted in science – we commissioned the Salford Energy House team to test different flow temperatures in the Energy House, to understand how this impacted gas use. The Energy House is a testing lab, including a traditional early 20th-century two-bedroom terraced house, set up in an environmental chamber and these tests were conducted with outdoor temperatures of 4.5°C, to simulate average UK winter temperatures.

Our research revealed about 15 million condensing combi boilers in the UK could be optimised by turning down their flow temperature, for a gas saving of 8%. The potential household saving for reducing boiler flow temperatures from 80 to 60 degrees was around £112 and 173kg carbon per year – in the summer of 2022.

In 2022 only 1 in 10 households reported changing their boiler flow temperature in the past year – and many reported being nervous about changing settings on their boiler in case they broke it.

The online tool

To address this, we created an online tool hosted on the website to show households how to turn their boiler flow down safely, using a step-by-step guide.  In October 2022 we launched a national campaign to raise awareness of this energy saving measure and the online tool.

Working in partnership with eight national partners and hundreds of supporters from housing associations to local authorities and advice-givers, we shared the message over the winter months to help people save money and energy. Close consultation with the UK Government on the development of the Help for Households campaign, where we advised the government using our evidence, led to the Money Saving Boiler Challenge featuring as the top tip for households to save money. We also saw support from Martin Lewis and Money Saving Expert who shared our message with the nation.

From October 22 to March 23, we saw more than 214,000 uses of our online tool to adjust the flow temperature on a combi boiler. We also know that through our radio campaign, and ours and others’ influence on government and energy companies, the evidence and advice we created reached many more people through other channels – generating a much greater scale of impact.

In early October 2022, 21% of people said they had lowered their boiler flow temperature in the past. This rose to 32% when we re-ran our survey in March 2023. We estimate this equates to approximately ~3.1m households turning down their boiler flow temperatures over the course of the campaign – saving an estimated 500,000 tonnes in CO2 and nearly £300m in savings for households and £157m for HM Treasury (reduced spending on the Energy Price Guarantee).

Helping others make the change

With autumn upon us and many people looking to turn their heating on in the coming weeks, the online tool at has been updated to reflect the latest savings based on the new energy price and the fact that Ofgem have revised annual gas usage for the average home from 12,000 kwh to 11,500 kwh.

If you want to support customers or households you work with to save money and energy this winter, you’ll find everything you need to feature the campaign on your external and internal channels in this supporters’ media pack. We’ve included a campaign overview, suggested copy for partners and supporters, a suite of creative assets.