In 2018 we launched Boost’s Winter Wallet; our first article explored how we delighted customers by thinking beyond energy; today we’ll look at how we improved the service.
Winter Wallet was our response to a problem we found through discovery research: pay-as-you-go energy customers often struggle to cover the costs of higher energy use during winter months. So we designed a scheme to help them save up in advance.
Analysing our Winter Wallet pilot
Our first version of Winter Wallet was a success — we helped our customers collectively save over £1,000,000. But when we analysed saving behaviours and survey feedback, we saw that 70% of people who joined the scheme didn’t actually meet their savings target, and 30% didn’t save at all.
Our key learnings:
- Not enough time to save
Launching the scheme near the end of summer made it challenging
for people to save as much as they wanted in time for winter - Customers weren’t motivated to keep saving Our experimental features to encourage people to contribute more
money to their Winter Wallet weren’t very effective - Our savings incentive didn’t impress While people valued a way to help them save, our 5% fixed bonus
would only earn, for example, £2.50 on a £50 savings target
2019: Winter Wallet v2
Our second run of the scheme gave us an opportunity to increase the initiative’s impact.
We wanted to help those who struggled the most to save by offering a savings scheme that people can easily stick with — maximising both engagement, and total money saved.
Humans find it difficult to reliably predict their future behaviour; we like to think of ourselves as rational creatures. In reality, we often act in irrational ways. So rather than interview customers to see how we could redesign Winter Wallet to help them save better, we turned to behavioural economics for fresh insights.
Automating saving to reduce friction
In his book Designing for Behaviour Change, Stephen Wendel recommends three strategies for changing behaviours:
Our original solution for the trial was basic. We tried to build a habit of customers saving into their Winter Wallet by prompting them during existing routines, like when they added credit to their balance. But this meant they still had to consciously decide how much (if any) to add to their Winter Wallet.
Saving for the future is hard if you’re financially struggling today. It can be mentally taxing every time you face the decision to put money away to help your ‘future self’ over your immediate needs now.
So we chose to experiment with the Cheat strategy by automating savings: we designed a straightforward set-and-forget mechanism where people could set their savings target and Boost would do the rest. Each day a small amount of credit would automatically transfer from their energy balance to their Winter Wallet to ensure they met their target on time. Customers also needed to be able to handle unpredictable life events so we made it easy for them to lower or pause their contributions.
Incentivising people to start, and continue, saving
Now we had an idea to automate savings, we conducted an analysis of contemporary behaviour change research to draw out insights to guide us further. We learnt:
- Non-savers are 70% more likely to show interest in a prize-linked savings account than savers.
- Research shows people are more likely to choose a gamble over a guaranteed fixed reward — suggesting that a ‘chance to win’ mechanic could be a more cost-effective way of encouraging people to save
- South Africa’s First National Bank found that a prize-linked savings account was more effective at helping those who are financially struggling than a fixed-interest one
- Research has also shown that low-income groups are the most likely to gamble on scratchcards and lotteries
This led us to a hypothesis that a prize draw mechanic could better motivate customers to both start, and continue, saving. We could run a monthly prize draw for all savers offering a chance to win various amounts of energy credit, including free energy credit for a year.
De-risking through experiments
As we further developed our new approach to encouraging people to save, we were conscious we had no evidence that these research insights would work in our context.
We treated the prize draw as an experiment so we could explore different ways to distribute prizes and see how winning different amounts impacted customer’s likelihood to keep contributing to their Winter Wallet.
We made two explicit assumptions:
- winning any prize will make you more likely to continue saving, compared to winning no prize
- winning a low value prize will make you less likely to continue saving, compared to winning a higher value prize.
We tested these assumptions in our first monthly prize draw. The results showed our first assumption was correct — customers who won a prize were more likely to continue saving. Interestingly, our second assumption was wrong — we found that people who won £1 were more likely to continue saving than people who'd won £2.

This led us to try replacing our £2 prizes with 50p ones instead. The results of this experiment showed that people who won 50p were more likely to continue saving than people who won £1. We applied these insights to the remaining monthly prizes draws to help us maximise the number of customers saving.
Promoting Winter Wallet
After optimising Winter Wallet v2, we focused our efforts on promoting it to maximise its adoption. The monthly prize draw was used to drive a sense of urgency to sign up, and we saw engagement peak before each prize draw.
By A/B testing our promotions at different times in the month, we learnt how to optimise things further; for example, sending an SMS the evening before a prize draw was twice as effective at encouraging sign up compared to those sent on other days.

Did our changes help more people save?
Yes! More than 30% of our customers took part, each saving over £100 on average.
The prize draw mechanic proved an effective means of encouraging saving behaviours from people who find saving challenging. Adoption peaked in the days before a prize draw as customers didn’t want to miss out. And those already saving tended to avoid pausing towards the end of the month when the potential of winning a prize was near.
Customer feedback showed how much our customers valued being empowered to save.
In summary
- When you’re trying to encourage people to change their behaviour, do your research; not just user research, but academic literature too. Behavioural economics helped us understand what interventions had successfully influenced similar behaviours to those we were targeting
- Treat your interventions as experiments, and find ways to test different variables and their impact on behaviours
Further reading
- Designing for Behavior Change – Stephen Wendel
- Thinking, Fast and Slow – Daniel Kahneman
- Engaged: Designing for Behavior Change – Amy BucherSmall Change: Money Mishaps and How to Avoid Them – Dan Ariely & Jeff Kreisler