Blockchains — open distributed ledgers of transactions — are emerging as an important technology for tackling community energy issues and the integration of renewable energy (see also G. Chapron Nature 545, 403–405; 2017). Consumers are increasingly generating their own energy by investing in solar panels and micro-wind installations. In Scotland, for example, more than 300 community energy projects are in operation ( Blockchains operate in a decentralized way that allows individual consumers to trade energy with each other. This removes the need for an intermediary utility company, thus assuring competition is fair. Blockchains ensure that the energy supply is traceable and that demand in one area is met by locally sourced renewable energy, where feasible. This peer-to-peer electron trading reduces carbon footprints and keeps revenues in the community. Blockchain-enabled 'smart contracts' guarantee that agreements between individuals are automatically implemented. The technology is still in its infancy. However, major challenges such as the computational cost of verifying transactions are being overcome — for example, by using algorithmic solutions to verify transactions in a distributed way.