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Old 04/07/10, 08:50 PM
Join Date: Nov 2009
Posts: 571
How much energy does a 1 1/2 hp well pump consume?

I'm trying to figure out if I should shell out $$$$$$$$ for a solar operated well pump or simply hook a cheapie into the main panel and run it off the main solar system. The guy at TSC couldn't give me a straight answer to how much power it uses. He said the pump is 220v. I will need a big pump because the wells in the area I'm looking at land in are up to 300 feet deep.
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Old 04/07/10, 09:55 PM
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Join Date: Feb 2004
Location: Out in the Boonies.. In Ohio
Posts: 792
1 H.P. is 746 watts. 1.5 would be 1119 watts @ 220 v.a.c.

Around 5 amps @ 220 v.a.c. (Free Flow)

Around 20 amps through an inverter using a 48 volt D.C. system. This would increase as the pump pressures up.
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Old 04/08/10, 10:16 AM
Join Date: Jun 2007
Posts: 1,064
Isn't the pump's horsepower rating it's output, not the imput required to power it. I normally assume that equipment is approximately 1/3 efficient, so a pump what outputs 1.5 hp (1120 watts) would require about 3360 watts to power it.

In any case, all electric motors/pumps will have a placard mounted on it that tells you specificly its voltage, wattage, amperage; so have the seller open up the box and read the wattage consumed. Remember to top it off with at least 50% starting watts.

I think your cheapest alternative though might be a regular AC pump powered by a gas or propane generator. That's what our homestead has and has worked well since 1980 (when the well was drilled). We pump our water into a holding tank and then use water on demand by gravity flow. By the way, you don't need a "big pump", you need a high pressure pump. You'll need a pump that can put out at least 150 psi to get out water if it's down 300 feet. Even more if you want to pump uphill to a holding tank. There are two considerations here. The pressure, and also the volume of water pumped out at that pressure. Ten gallons per minute at 150 psi is a bigger pump than 5 gallons per minute at 150 psi. I'd suggest that if you're on the grid with this pump, a smaller gpm rating might be OK. If you have to start up a generator to pump, then the least time the generator is running the better, so a higher gpm pump might be more practical.

Last edited by Michael Kawalek; 04/08/10 at 10:24 AM.
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Old 04/08/10, 07:23 PM
Join Date: Feb 2007
Location: Wisconsin
Posts: 964
Can you solar setup supply 3000 watts to the pump? If not, you need to rethink your pumping strategy. Less gpm means less wattage, but longer running. The standard deep well centrifugal pumps are terribly inefficient. My 4" Flotec starts on 9 amps, then goes down to 7amps for pumping from 115'. This is supposed to be a 1hp pump, and its using 2 1/2 hp's worth of energy.

You really need to know what the depth of the water is, and how much you need. Our well is 297', but water is at 115'. If I wanted to I could use a bubble pump to get water to a cistern, and then use a RV style diaphragm pump to pressurize the water.

You can buy a lot of gas to power a generator for pumping for the price of a Grundfoss solar pump. They are fantastic, but the price is very high.

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Old 04/10/10, 12:48 AM
Join Date: Mar 2005
Location: Colorado
Posts: 2,339
yes you may need the 3000 watt generator to power the pump but the starting amp requirements can be 3 to 4 times more than the run amps,

most motor are not 100% efficient but I have always used a rough estimate as a 1000 watts as a hp, instead of the 746 as in reality the 1000 do to losses and heat and friction is closer IMO. so I would figure 1500 watts for the pump,
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