The invention discloses a power grid supply and demand interaction method through smart home. A multi-level water heater cluster is adopted as a control load group, user water consumption and power grid consumption tasks are comprehensively considered, the opening-closing state of each single water heater is considered, and control tasks are subdivided into selection of the operating power level of each single water heater through a genetic algorithm. The method aims to achieve precise load regulation and the required consumption task through flexible combination of the power levels of all thewater heaters.