sentences:  The efficiency of a computer power supply is its output power divided by its input power; the remaining input power is converted into heat.For instance, a 600-watt power supply with 60% efficiency running at full load would draw 1000 W from the mains and would therefore waste 400 W as heat.On the other hand, a 600-watt power supply with 80% efficiency running at full load would draw 750 W from the mains and would therefore waste only 150 W as heat.