£1 discount on product swaps shifts UK shoppers towards greener food choices

A study led by Thijs van Rens, Professor of Economics at the University of Warwick, shows that offering product swaps that include financial incentives of up to £1 off the price while online shopping can significantly shift consumer behaviour towards healthier and more environmentally sustainable food choices.

The research, presented to Westminster policy makers at Nesta yesterday (18 March), tested whether price incentives and eco-labels could encourage shoppers to swap products for greener alternatives during their weekly online grocery shop. The results show that a well-targeted £1 discount on more sustainable alternatives measurably reduced the environmental impact of shoppers' overall baskets.

With the UK food system responsible for around 38% of national greenhouse gas emissions, according to the Government's Food Strategy for England, helping consumers make lower-impact choices is seen as a key part of reaching climate targets.

Thijs van Rens, Professor of Economics, University of Warwick, said: "Food currently makes up a very large part of greenhouse gas emissions, and we cannot reach Net Zero without changing what we eat - changing our diets is imperative.

"But we cannot expect consumers to foot the bill for this, especially not at a time when a lot of people are already struggling to get by.

"What we show in this trial, is that we need to fix prices: food that does not harm the planet should not cost shoppers the earth. If there is an alternative available that is affordable, easy to find, and clearly better for the environment, then people are willing to give it a try."

Digital tools for sustainability research

The results stem from a large-scale, eight-week randomised controlled trial involving 1,835 UK online grocery shoppers. Shoppers made choices through a bespoke browser extension, developed by environmental tech company Sustained, that offered alternatives, discounted alternatives, and environmentally labelled products while they did their online shop.

Importantly, participants shopped with their usual supermarket and were delivered their groceries as usual, but they consented for the browser extension to collect data on their shopping behaviour for the research.

Labels alone do not change behaviour

The study also assessed the impact of prominent colour-coded A-G eco-labels, similar to nutrition traffic-light labels, which show the environmental footprint of different foods. However, eco-labels on their own did not significantly change purchasing behaviour towards greener products.

Labels became far more effective when paired with price incentives. When the £1 discount was combined with eco-labels, the behavioural impact more than doubled, suggesting that labels help reinforce the credibility of the cheaper greener option.

Implications for policy

The economic and policy implications of this study are three-fold:

1. Economic incentives do shift food purchasing to promote sustainable grocery shopping effectively.

2. Eco-labels should not be expected to change behaviour on their own. However, when incorporated into pricing policies or promotional strategies, they offer a powerful informational boost.

3. Digital trials like this reduce the cost and complexity of pilot programmes and generate robust, real-world evidence before national rollout.

ENDS

Notes to Editors

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Image Credit:

• Credit: University of Warwick
• Description: Professor Thijs van Rens, University of Warwick (left); Professor Oyinlola Oyebode, Queen Mary University of London (right)

About this research

The online shopping project is part of the SALIENT food trials, a consortium of eight universities and two research institutes looking at ways to support healthier eating and reduce the impact of food on the planet, funded by the UK government through the ESRC.

Professor Thijs van Rens will continue his research tackling healthy, sustainable diets and Net Zero goals with new UKRI-funded THRIVING project. Thijs will lead a team creating novel digital tools, such as smartphone apps, to collect data and evaluate the effect of interventions in real-world shopping environments such as food delivery apps.

About SALIENT

The SALIENT consortium is drawn from eight universities (Oxford, Cambridge, Warwick, Birmingham, Hertfordshire, Liverpool, London School of Hygiene and Tropical Medicine, and Queen Mary University of London) and two research institutes (Nesta and the Behavioural Insights Team). The consortium is led by Professor Pete Scarborough from the University of Oxford, and Professor Martin White from the University of Cambridge. They regularly meet with a Programme Board with members from the following Government departments: Department of Food, Environment and Rural Affairs; Food Standards Agency; Cabinet Office; HM Treasury; Department of Health and Social Care; Department for Levelling Up, Housing and Communities; Department for Education.

About the University of Warwick

Founded in 1965, the University of Warwick is a world-leading institution known for its commitment to era-defining innovation across research and education. A connected ecosystem of staff, students and alumni, the University fosters transformative learning, interdisciplinary collaboration, and bold industry partnerships across state-of-the-art facilities in the UK and global satellite hubs. Here, spirited thinkers push boundaries, experiment, and challenge conventions to create a better world.

19 March 2026