The wealthy have an outsized impact on many real-world public goods problems, consuming vastly more resources per capita than less wealthy individuals. This creates a challenge for motivating the wealthy to engage in more sustainable behaviors; because of their wealth, they are not very responsive to economic incentives (e.g. fees, fines and taxes) of the magnitudes typically employed. We propose that “social incentives” (which rely on social normativity and reputational concerns) may be more effective for motivating the wealthy. To test this claim, we conduct a field experiment aimed at reducing residential water use among 10,500 relatively high-income households in the state of Connecticut (estimated 137% wealthier than the average US household). We compare a control condition (receiving no messages) to a messaging campaign (5 messages sent over 9 months) that emphasizes either self-interested financial benefits of water reduction (“Private Benefit” treatment) or the benefits of water conservation for the community and the environment (“Public Good” treatment). We find that the Private Benefit treatment had no significant effect on water use compared to the control. The Public Good treatment, on the other hand, significantly reduced water use relative to the control and relative to the Private Benefit treatment, and this effect was especially pronounced among households with previously higher water use (a commonly used proxy for wealth). Our findings suggest that non-material “social incentives” may be more effective than traditional financial incentives for encouraging sustainability, particularly among the wealthy.