always has to run. You may not see a gain with switching to electrical driven water pump. You would be switching the load from the water pump and fan to the alternator which takes horsepower. Electric fans come in all flavors. The size and shape of the fan blades determines the amount of power it takes to spin up to a certain rpm. If you have a 30 amp elecric fan that will take 360 watts to operate at full load. One horsepower is 746 watts. The electric fans don't have to run all the time or at full speed.