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Solar Pump Sizing.
Solar Pump Sizing Calculator
Off-grid water pumping. Daily volume + total dynamic head → pump size → solar panel size + battery + storage tank.
Total Dynamic Head (TDH) explained
TDH is the total resistance the pump must overcome:
TDH = Static head (vertical lift)
+ Friction loss (pipe + fittings)
+ Pressure head (any required PSI × 2.31 ft/psi)
+ Suction lift (if pump above water)
Friction loss adds up — a 200 ft run of 1" pipe at 5 GPM adds about 15 ft of head. Use the next size up if uncertain.
Pump types
| Pump | Best for | Power | Lift capability |
|---|---|---|---|
| Diaphragm (e.g., Shurflo, Aquatec) | Low flow, modest lift; livestock, RV | 12V or 24V DC | Up to ~100 ft |
| Centrifugal surface | Flooding fields, transferring; needs water at pump | 12-48V DC or AC | 20-30 ft suction lift, push much further |
| Submersible centrifugal (Grundfos SQF, Lorentz) | Wells; the workhorse | 30-300V DC, brushless | Up to ~600+ ft |
| Submersible helical rotor (positive displacement) | Wells with low yield; deep wells | 30-200V DC | Up to ~750 ft; constant flow at varying speed |
| Ram pump (no electricity) | Flowing water source | None — uses water hammer | ~10× the drop you have |
Storage strategy comparison
| Pump-to-tank, gravity-feed | Battery bank | Direct DC (no battery) | |
|---|---|---|---|
| Capital cost | $$ tank + pump | $$$ batteries + controller | $ pump only |
| Reliability | Highest (mechanical only) | Battery wear in 5-10 yrs | Pumps only when sun |
| Pressure constancy | Constant (gravity) | Constant | Variable with sun intensity |
| Best for | Most rural/remote | Domestic use; need pressure on-demand | Pond fill, irrigation timing-flexible |
Tank + gravity-feed is the dominant rural pattern. Pump runs when sun is up, fills tank; gravity delivers pressure to drip lines or troughs all day/night.
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