Community energy projects take a decentralised and participatory approach to low-carbon energy. We present a quantitative analysis of business models, financing mechanisms and financial performance of UK community energy projects, based on a new survey. We find that business models depend on technology, project size, and fine-tuning of operations to local contexts. While larger projects rely more on loans, community shares are the most common and cheapest financial instrument in the sector. Community energy has pioneered low-cost citizen finance for renewables, but its future is threatened by reductions, and instability, in policy support. Over 90% of the projects in our sample make a financial surplus during our single-year snapshot, but this falls to just 20% if we remove income from price guarantee mechanisms, such as the Feed-in Tariff. Renewed support and/or business model innovations are therefore needed for the sector to realise its potential contribution to the low-carbon energy transition.