A promise of cloud computing is the reduction of energy footprint enabled by economies of scale. Unfortunately, little research is available on how cloud consumers can reduce their energy footprint when running software in the public cloud. Moreover, cloud consumers do not have full access to information regarding their cloud infrastructure usage, which is required to understand the impact of design decisions on energy usage. The purpose of our study is to support cloud consumers in developing energy-efficient workloads in the public cloud. To achieve our goal, we collaborated with a large cloud solution provider to discover an initial set of reusable architectural tactics for software energy efficiency. Starting from interviews with 17 practitioners, we reviewed and selected available tactics to improve the energy efficiency of individual workloads in the public cloud, and synthetized the identified tactics in a reusable model. In addition, we conducted a case study to assess the impact of utilizing a tactic, which was selected following a prioritization provided by the practitioners. Our results demonstrate the possibility to architect cloud workloads for energy efficiency through reasoning and estimation of resource optimization. However, the process is not (yet) straightforward due to the current lack of transparency of cloud providers.