Skip to content
OASIS
LivingIQ

Solar Well Pumps

Sizing a Solar Well Pump for a 300-Foot Well

Total dynamic head, not depth, decides your pump. Here is the arithmetic and the array size it lands on.

11 min read Intermediate
Water storage tank fed by a solar-powered well pump on a homestead

The question I get most often is whether solar can lift water 300 feet. It can. The real question is how much water, how fast, and into what.

Get total dynamic head right and everything else — pump model, array size, wire gauge — falls out of it.

Materials

  • DC helical rotor pump
  • Pump controller with dry-run protection
  • Submersible cable
  • Safety rope
  • Storage tank

Tools

  • Well sounder or weighted tape
  • Pressure gauge
  • Multimeter
  • Pipe wrenches

Estimated cost: $2,100–$3,400. Difficulty: Intermediate.

1.Measure static water level, not well depth

A 300-foot well often holds water at 120 feet. Drop a sounder and find the true static level, then note the drawdown during a pumping test. Everything downstream depends on this number.

2.Add up total dynamic head

TDH = static water level + drawdown + vertical rise to the tank + friction loss in the pipe + any pressure you need at the outlet. Ours: 140 + 25 + 60 + 12 + 0 = 237 feet. That, not the 300-foot casing, is what the pump works against.

Notebook showing total dynamic head calculations at a wellhead

3.Pick the pump family

Below about 2 gpm at high head, helical rotor pumps win on efficiency and they self-prime. Centrifugal pumps make sense above 5 gpm at moderate head. For a deep well filling storage slowly, helical rotor is almost always the answer.

4.Size the array to the pump curve

Read the manufacturer's curve at your TDH, not at the headline figure. Ours needs 620W to deliver 1.4 gpm at 237 feet, so we built a 700W dedicated array. Direct-coupled with an MPPT controller, no battery in the loop.

5.Design storage instead of pressure

Pump into a 1,500-gallon tank all day and pressurize the house from that with a small booster pump. This removes the surge load from your battery bank and gives you days of water if the pump ever fails.

Common questions

Can a solar pump run a 300-foot well?
Yes. Helical rotor DC pumps handle 300+ feet of lift on roughly 600–900 watts of array, delivering 1–3 gallons per minute through the day.
Do I need a battery for a solar well pump?
No. Pump to a storage tank during daylight instead — tank storage is far cheaper per usable gallon than battery storage.
Will it work on cloudy days?
At reduced flow. Size the storage tank for two to three days of household use so overcast stretches never reach the tap.
Ellis Hartwell

Written by

Ellis Hartwell

Twelve years building and rebuilding systems on 28 mountainside acres. Everything published here has run on this property or been documented on site with the owners.

The newsletter

Get the Homestead Dispatch

One letter every other Sunday: what we built this week on the mountain, what failed, and the numbers behind it. No fluff, no sponsored filler.