Residential and small commercial electricity consumers will provide most of the flexibility needed in the power system to achieve the energy transition at lower cost. This flexibility will allow the electricity grid to take on more renewables and need less grid reinforcements. Consumers are happy to participate (>75% opt-in rate) via an aggregator and be rewarded with energy savings reducing their electricity. Because it reduces the overall costs of running the energy system, it means that all consumers benefit from lower energy prices. The business case is now proven as more and more countries worldwide ensure demand side response can participate in wholesale markets as an alternative to generation and the EU has provided support through its recent Clean Energy Package. Pierre Bivas from Voltalis will share his experience of operating flexibility from more than 100,000 households in France, and now installing another 150,000, backed by the European Investment Bank, while also developing in other countries with local partners.