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Watts = GPH

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  • Watts = GPH

    Hello Solar Panel Talk,

    I've been searching for a graph or equation to help me calculate how many gallons of water I can pump (gph) on a level surface with 100 watts of solar power. Let's say at 70% efficiency.
    I expect this question has been asked before here but a search of watts = gph draws a blank. Please post a clear answer or point me towards one. THANKS! controlrod

  • #2
    You need to locate the pump curve for the pump you are looking at. Different pumps perform differently with different flow rates and head.
    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
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    • #3
      are you trying to circulate a pond or something? even then you wont have level head due to pipe friction. It is also worth noting that a lot of the solar pumps do better with more volts, so its not entirely about watts.


      • #4
        Just to give you an idea why the conversion is not simple:
        If you just let water flow from one tank to another which is a few inches lower, any GPH takes no power at all.
        But to get the same GPH from the bottom of a 200 foot well will take a lot more power.
        SunnyBoy 3000 US, 18 BP Solar 175B panels.


        • #5
          Lets assume that your panel will be producing about 5.5 amps of current, at noon, with perfect orientation. It might be able to power this pump I found on grainger.
          It appears to draw no more than 4amps, and it says it pumps 1.1 gallons per minute.

          For serious water pumping, not like this toy above, you can look at the charts for these pumps. Note that required wattage starts at ~400.