Year-round monitoring of Erebus volcano (Ross Island) has proved challenging due to the difficulties of maintaining continuous power for scientific instruments, especially through the Antarctic winter. We sought a potential solution involving the harvesting of thermal energy dissipated close to the summit crater of the volcano in a zone of diffuse hot gas emissions. We designed, constructed and tested a power generator based on the Seebeck effect, converting thermal energy to electrical power, which could, in principle, be used to run monitoring devices year round. We report here on the design of the generator and the results of an 11 day trial deployment on Erebus volcano in December 2014. The generator produced a mean output power of 270 mW, although we identified some technical issues that had impaired its efficiency. Nevertheless, this is already sufficient power for some monitoring equipment and, with design improvements, such a generator could provide a viable solution to powering a larger suite of instrumentation.