I have an e-fan and even did a how to on it recently. I haven't seen any real noticeable gains in mileage or hp. Thats not the reason I did it though. I did it to eliminate the loud ass clutch fan, which is just plain annoying when you're in city stop and go traffic, and so I can turn off the fan when crossing deep water. This keeps the water from splashing the engine and keeps the engine from bogging down. I didn't spend tons of money on it Maybe $60 total including all the wiring. It is wired very simple with solenoids and an on off switch so if something does go wrong I can fix the wiring on the side of the road, in a mater of minutes. In the worst case that the actually fan motor would fail, the truck can still be limped home. (I have had this happen before.) It is amazing how fast you can drop the engine temp just by turning on your heater. An electric fan will draw more electrical load, but that doesn't make the engine work harder. The alternator is not gonna be harder to turn with more of an electrical load on it. They already produce more output than needed, that is way they have regulators on them. Don't install one because you think your mileage or hp will increase, because what little gain you get will not be noticeable.

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2003 Ranger FX4 level II. 3" BL, 33x12.50 GT Radial Mud Claws, Custom front and rear bumpers with winch hookups, custom flatbed, with hi-lift, and full size spare mount, 12,000 lb winch mounted under bed, Electric fan, and of course a flowmaster.