This article extends the canonical harm reduction approach to a wider set of applications, including conservation. The authors develop an economic model to illustrate the trade-offs inherent to harm reduction, weighing the benefits of reducing harm against the risk of drawing those previously abstaining into consumption, and identify contexts where harm reduction is not applicable. Using sequential campaigns with embedded experimentation that enables measurement, the authors market a harm reduction solution in the context of water conservation. They show that a smart irrigation controller that efficiently maintains stigmatized ornamental landscapes appeals to the heaviest irrigators and generates large and long-lasting individual and social benefits: cost recovery in six months and water savings covering another household’s basic needs. The findings show no evidence that the controller cannibalizes abstinence (lawn removal) or increases irrigation by conservation-prone individuals. The conceptual and measurement framework provides a foundation for implementing and evaluating harm reduction well beyond the typical drug and public health contexts.