Electric Water Pump info please

If a water pump uses less power to operate it is only because it is pumping less water. Work is work. All else being equal, the electric will draw more load (amperage NOT voltage) due to some energy lost to resistance in the electrical system.

So why do drag racers like electric pumps? A few reasons:
1. They run at a constant speed, equivalent to say 2000 crankshaft RPM so in the staging lanes you can keep the engine cool with a small light radiator because you have a lot more circulation than you would have at idle.
2. With an alternator cutout, you can remove the pumping load and all others from the alternator temporarily during the pass, 30 seconds or so.
3. As you idle down the return road, your pump is running at it's constant speed so you can cool off quicker.
4. Back in the pits, with the car plugged in, you can leave the pump running to cool the engine between rounds.

So for a typical drag car they make sense. If you plan to cool a high horsepower big block with a lightweight little VW or Honda radiator, an electric water pump is probably mandatory.

So why not run one on the street?
1. They're expensive.
2. They're constant speed, so you will tend to overcool (no thermostat remember) at idle and at low speed, and undercool at high RPM like highway driving or road racing.
3. They're added complexity. Sure would suck to fry a $5000 engine because a $0.15 fuse blew.
4. Most aren't exactly weatherproof. Ever wonder what it's like under your hood driving down the highway when it's raining? Hide behind a car radiator during a hurricane and see how dry you end up.

If it were me, I would spend the money on a good crossflow radiator, and then a set of March underdrive pulleys. That way you could slow the belt drive pump down during sustained high RPM running. Remember, as pointed out above, the faster you spin the pump, the more water it moves, but the more work is required.

For endurance running consider simple, reliable, proven technology even if it means giving up a couple horsepower. Think about airplane engines, an O-360 Lycoming is ridiculously simple for a reason.