Several proposals are currently under evaluation for a future electron-positron collider which would provide unique opportunities for detailed studies of the Higgs boson. Any such facility would have a significant environmental impact, owing to its construction footprint and its energy consumption needs. In this paper, we evaluate the carbon impact of one of these proposals, the Cool Copper Collider (C$^3$). We introduce various solutions to reduce the power needs for C$^3$ without modifications in the ultimate physics reach. We also compare C$^3$ with other electron-positron colliders, planned to operate in a similar energy range, taking into account physics reach, energy needs, and carbon footprint for both construction and operation. We conclude that the compact 8 km footprint and the possibility for cut-and-cover construction make C$^3$ a compelling option for a sustainable electron-positron collider. More broadly, the developed methodology serves as a starting point for evaluating and minimizing the environmental impact of future colliders without compromising their physics potential.