Storage technologies – such as batteries or hydrogen – are crucial for a transition towards a low-carbon economy as they complement intermittent wind and solar power generation without the emission of carbon dioxide to the atmosphere. Rapidly growing shares of these renewables, combined with the requirement for profit of potential investments, make clarity on business models and profitability of energy storage both urgent and essential. Here we identify the business models of conceivable storage applications, match them with available storage technologies via overlapping operational parameters and systematically examine opportunities and barriers for profitability, including supportive policy measures and priorities for research and development. Existing technologies could meet the need for storage in the power market, but widespread profitability relies on advances in both economic utilization and technological innovation.