Brownouts are sometimes caused by overloaded circuits and are sometimes caused intentionally by the ac utility company in order to reduce the power drawn by users during peak demand periods ( like during hot summers when everyone is using their air conditioners ) 有时电路过载会引起电灯暗淡，有时供电公司有意这样做，是为了在用电高峰期内降低用户的用电量（比如在盛夏，每家人家都在使用空调） 。
