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mja1, sure on the street, if you're running electrical devices off an alternator, then there's not much of a benefit since the engine only needs to turn say 3000rpm on the street. But once you start using the higher revs say in performance driving, or if you have a set up that gets electrical energy from a more efficient source, then an electric pump makes quite a bit of sense. Since alternators these days attempt to generate more energy under favorable circumstances, the efficiency loss is mitigated somewhat.
I suspect that under low load like on the highway the pump is likely spinning a little too fast already, and since pumping power is approximately the cube of speed, you only need it spinning <30% faster than it needs to before an electric pump spinning at the appropriate speed with 50% efficiency breaks even.
I don't think anyone is talking about turning the pump off, just reducing the speed.
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