Upgrade mechanical fan vs installing electric fan

The horsepower is of course the loss to the car engine to drive a fixed pulley belt driven fan.The power loss to the engine goes up by the cube of the engine and fan speed. All of the air moved at a high fan rpm is not needed to cool the engine. A fan clutch allows the fan to run at lower speeds and save a lot of engine horsepower. Electric fans run at constant speed, only when needed, and save even more engine power. Maybe we can find some actual comparison numbers for a car at an electric fan website.
Static pressure is the resistance to the airflow caused by pipes, baffles,etc. Measured in inches of water. It is usually used as a constant in fan charts.