Blockchain-based cryptocurrencies have become an extremely important, highly-used, technology. A major criticism of cryptocurrencies, however, is their energy consumption. In May 2022 Bitcoin alone was reported to be consuming 150 terawatt-hours of electricity annually; more than many entire countries. Hence, any meaningful efficiency increase in this process would have a tremendous positive impact. Meanwhile, practical applications of quantum information technologies, and in particular of near-term quantum computers (NISQ) continue to be an important research question. Here, we study the efficiency benefits of moving cryptocurrency mining from current ASIC-based miners to quantum, and in particular NISQ, miners. While the time-efficiency benefits of quantum technologies is extremely well-studied, here we focus on energy savings. We show that the transition to quantum-based mining could incur an energy saving, by relatively conservative estimates, of about roughly 126.7TWH, or put differently the total energy consumption of Sweden in 2020.