What are the environmental impacts of using batteries to power large-scale IoT deployments? While IoT can help organizations save energy and improve operations, the batteries used in wireless sensors create carbon, maintenance, materials, and disposal problems over the life of each device. This paper includes a Circular Ecology study comparing the carbon footprint of the same IoT sensor powered by an AAA battery, a CR2032 coin cell, and Lightricity’s indoor photovoltaic cells over 25 years, showing that the PV-powered version can reduce carbon footprint compared with battery-powered alternatives.