Frankly I am surprised with today's high-power semiconductors that a 120VAC motor doesn't have a controller built-in to drive them at higher efficiencies. JKB is right on the money for 3-phase.
One of my projects I am hoping to do next summer is have an excavator put in a cistern pipe (galvanized drain pipe with holes) in a spring near my pond, hopefully 20 or more feet down (surface well). Then I intend to drop a solar-powered pump down there in order to help keep the pond topped off rather than digging a full-fledged well. One of my goals is very high efficiency so I can learn about current solar products and installations. I don't even know if a DC motor is better than AC, or what should be used for a solar installation. I am still a long ways off since I don't even know what kind of flow rates I will get from this spring, if I need to cycle on and off or continuous, if I need batteries and a controller, or straight solar to pump will work. Of course I want it to be priced reasonably as well... A lot of work to do.
My neighbor just installed solar panels on his roof, and his panels that I thought were about 150W a piece are actually 340W a piece! The efficiency gains are incredible on solar lately. For the cost of a meter on a pole for access to the power grid ($25 a month), I can buy 2-3 of these panels a year. Add in the electric cost and it pays for the whole installation in 2-3 years based on relatively low flow rates. I don't need a lot of flow to make up for my 1/10" loss a day on a 0.6 acre pond, but this is the most reasonable solution I can come up with.
My biggest problem will be how to secure the equipment so it doesn't get stolen.
Eric, where about are you? I am south of Rochester... maybe solar would be a good solution for you as well.
