The transition to power grids based on a majority-renewable generation mix is widely held to depend on the ability of grid operators to smooth out spikes in demand and intermittent supply. Efforts are under way to bring as many players as possible – industrial and commercial end-users as well as generators – into the balancing market, and to use smart meter technology to help on the demand side. But a large-scale deployment of batteries is also seen as key to solving the problem, and a study of