Defaults beat discounts: how one checkout setting takes sustainable delivery from 7% to 75%, without costing you a cent in margin.

Amsterdam, August 25, 2026 – Online retailers that choose to pre-select the sustainable delivery option in checkout see the share of sustainable deliveries rise from roughly seven to 75 percent. By comparison, even a one-euro discount on shipping costs increases that share to no more than around twenty percent. This was revealed by a field experiment conducted jointly by logistics SaaS platform Wuunder and the University of Groningen in the live checkout of the online shop SOXS.co.

Offering discounts costs money 

Over an eight-month period, researchers tracked consumer delivery choices. The study examined the effect of the pre-selected delivery option (default), information provision (such as sustainability labels), and financial incentives (a discount of fifty cents or one euro on shipping costs for the sustainable option).

Most webshops set fast delivery as the default in the checkout process. Under that setting, about seven percent of consumers actively opted for the more sustainable, postponed delivery. When sustainable delivery is pre-selected, that share rises to 75 percent. The test evaluated not only the effects of pre-selection, but also the impact of a financial incentive. A one-euro discount on shipping costs brought the share to twenty percent, while a fifty-cent discount raised it to fifteen percent.

Adding a sustainability label also yielded little change, with one in ten consumers choosing sustainable delivery after the label was introduced. A more effective way to shift consumer choices is combining the pre-selected sustainable option with a discount and a label, which raised the share of consumers to roughly ninety percent.

Webshops choose the most expensive route 

In practice, many online retailers still rely on checkout tools that, according to the research, deliver the lowest returns. Of the one hundred webshops surveyed, more than a third (38%) offer no sustainable delivery option at all. Of the 62 stores that do offer one, just over half (51.6%) rely on discounts and a quarter (25.8%) on information provision. Only eight of these 62 webshops have the sustainable option set as the default.

From insight to checkout 

Wuunder and the University of Groningen have previously collaborated on sustainable logistics research. This aligns with the company's trajectory: Wuunder was among the first shipping platforms globally to achieve B Corp status. This certifies that Wuunder meets international standards for social and environmental impact, evaluated by an independent body to verify that sustainable ambitions are genuinely embedded in business operations.

Jeroen Gehlen, founder of Wuunder: “Every day, we see how much money leaks away in the checkout process. Webshops invest in discounts and green labels because it feels logical, but the results of this study show a different reality. Pre-selecting the sustainable option changes customer behavior significantly at zero cost. Every customer who chooses a green delivery day enables a thirty-percent cost reduction in the warehouse. For parcel delivery, that translates to twenty percent fewer delivery vans on the road and a 7.5 percent reduction in CO₂ emissions. Why should a retailer pay for discounts that have hardly any effect, when the free intervention delivers the best result? That is where the opportunity lies for us: sustainability that protects margins without requiring extra effort from the customer.”

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More information about  Wuunder Best-Day-Delivery Checkout