Power, Heat, & Efficiency?

Question

An 800MW electric power plant has an efficiency of 30%. It loses its waste heat in large cooling towers. Approximately how much waste heat is discharged per second?

Answer 1

An 800MW plant running at full load produces 800 MW of electric power. This is 30% of its total power output.  The rest (70%) is the waste heat.  Therefore the waste heat power output is 800 x 7 /3 =1867MW.  The plant therefore discharges 1867MJ in waste heat every second.