With their proportion increasing gradually, air conditioners can be a feasible option to provide certain amount of reserve for microgrid. A clustered model based on first-order physical model is provided according to the heat exchange balance. The model can depict appropriately the working characteristics of air conditioners. Considering load response characteristics, a frequency adjustment model is provided, which conditioners’ setting temperatures are inversely proportional to grid frequency. This frequency adjustment model reduces the influence to users’ comfort. Simulation results verify the effectiveness and usefulness for clusters air conditioners, providing reserve for microgrid.