Reducing CO₂ emissions from fossil fuel- and biomass-fired power plants often also reduces air pollution, benefitting both climate and public health. Here, we examine the relationship of climate and health benefits by modelling individual electricity-generating units worldwide across a range of climate–energy policy scenarios. We estimate that ~92% of deaths related to power plant emissions during 2010–2018 occurred in low-income or emerging economies such as China, India and countries in Southeast Asia, and show that such deaths are quite sensitive to future climate–energy trajectories. Yet, minimizing future deaths will also require strategic retirements of super-polluting power plants and deployment of pollution control technologies. These findings underscore the importance of considering public health in designing and implementing climate–energy policies: improved air quality and avoided air pollution deaths are not an automatic and fixed co-benefit of climate mitigation.