The economic value of electrical energy depends on consumption and availability. On the power exchange, low prices are caused by supply surpluses from wind turbines, for example, while high prices are caused by bottlenecks – when power plants fail or less electrical energy is provided by renewable energy sources. Arbitrage in the electricity market, as in all other markets, is a way to make a profit. This involves storing electricity in a battery storage system when the price for it is low. If the price rises, the stored electricity from the storage system is fed into the grid.