A megawatt is 1000 kilowatts (also equal to 1341 horse power) or 1*10^6 watts, a gigawatt is 1000 megawatts. A watt is equal to one joule per second and a joule is defined as the amount of work done when 1 ampre of electrical current is passed through 1 ohm of resistance. Ohm is defined as the amount of electrical resistance of a conductor in which 1 ampre of current is produced by a potential of 1 volt across its terminals.