The cost of batteries is falling to the point that they are becoming an increasingly viable option for uses such as supporting the stability of power grids, according to Lazard, the investment bank. Electricity storage has until recently been prohibitively expensive, but its emergence at an economically viable cost will enable increased use of wind and solar power, which are not always available. The cost of renewable energy has fallen sharply over the past decade as market growth, usually encouraged by subsidies, has enabled manufacturers of wind turbines and solar panels to benefit from economies of scale. Similar trends are now at work in electricity storage with investments such as Tesla’s battery “gigafactory”, now under construction in Nevada, greatly increasing manufacturing capacity.