This paper considers the structural similarities in approaches and lessons learned in the development of applications for behavior change in water and energy saving. We show how the domains of water and energy are related and propose a first set of design guidelines for building such solutions, especially regarding visualization and gamification of water and/or energy consumption. We exemplify how such guidelines can be applied with the designs and prototypes of a gamified application for water saving behavior change from our SmartH2O project. Based on feedback from user and stakeholder workshops and online discussions, we discuss how the initial design guidelines synthesized from the literature have been refined. In a next step, we will validate them by deploying the implemented prototype in realworld trials with several thousand smart-metered households in the UK, Switzerland and Spain.