How much water do I need for micro hydro?

Head and flow together decide it. As a rough gate: 20 feet of head with 20 gallons per minute can produce useful continuous power; below that, spend the money on solar instead.

Do I need a water rights permit?

Almost certainly. Diversion for power is regulated in most states even when the creek is on your own land. Check before you buy pipe.

Is micro hydro better than solar?

When the site supports it, yes — it produces 24 hours a day, which shrinks the battery bank you need. But most properties do not have the head and flow to justify it.

Micro Hydro

Is Your Creek Worth a Micro Hydro Turbine? Measure These Two Numbers First

Head and flow decide everything. Two afternoons with a hose and a bucket will tell you whether to keep reading or go back to panels.

10 min read IntermediateJanuary 27, 2026

Small mountain creek running through mossy rocks in a forest hollow

Micro hydro is the best power source on a homestead when it works — 24 hours a day, indifferent to clouds, and cheaper per delivered kilowatt-hour than anything else we run.

It is also the easiest to talk yourself into on a creek that dries to a trickle in August. Measure first, in the driest week of the year.

Materials

100 ft garden hose
5 gal bucket
Pressure gauge with hose fitting
Stopwatch

Tools

Measuring tape
Notebook
Stakes and string

Estimated cost: $25 in measuring supplies. Difficulty: Intermediate.

1.Measure head with a hose and a gauge

Run the hose from your intake point down to the proposed turbine site, fill it, cap the low end with a pressure gauge and read the static pressure. Multiply psi by 2.31 to get feet of head. Our north branch reads 41 psi — 95 feet.

Pressure gauge attached to a hose at the bottom of a hillside water run

2.Measure flow in the driest week

Dam the creek temporarily so all flow funnels through a pipe and time how long it takes to fill a 5-gallon bucket. Five seconds is 60 gpm. Do this in late August, not April, or you will design for water you don't have.

3.Calculate realistic output

Watts ≈ (head in feet × flow in gpm) ÷ 10, allowing for typical system efficiency. Our 95 feet and 22 gpm dry-season flow gives roughly 209 continuous watts — about 5 kWh a day, which is more than our array makes in December.

4.Check the legal side before the technical side

Water rights vary enormously by state. In some places diverting and returning flow needs nothing; in others it requires a permit even when the water goes back to the same creek fifty feet downstream. Call before you dig.

Common questions

How much water do I need for micro hydro?: Head and flow together decide it. As a rough gate: 20 feet of head with 20 gallons per minute can produce useful continuous power; below that, spend the money on solar instead.
Do I need a water rights permit?: Almost certainly. Diversion for power is regulated in most states even when the creek is on your own land. Check before you buy pipe.
Is micro hydro better than solar?: When the site supports it, yes — it produces 24 hours a day, which shrinks the battery bank you need. But most properties do not have the head and flow to justify it.

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.

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