YSK: Your dishwasher is far more energy / water efficient than you are at washing dishes. Running a dishwasher that is only 25% full will still use less water, on average, than hand washing those dishes. Save water, energy, and time by using your dishwasher instead of washing by hand.
from /r/YouShouldKnow
YSK：你的洗碗机比你洗碗时更节能/节水。在洗碗机只装满25%的情况下，其平均用水量仍比手洗餐具少。使用洗碗机而不是手洗，可以节约水、能源和时间。