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Generation · Hydro

The one source that runs all night in February.

Solar stops at dusk. Wind stops when the air does. A stream with real drop and steady flow does neither, which is why moving water is the best generation resource on this site wherever it exists.

Most properties do not have it. This section starts by helping you find out, honestly, whether yours does.

The eight guides Does my property qualify

Before anything else

Four things have to be true at once.

Water power asks more of a site than any other source in this section. A property qualifies when it has moving water with vertical drop, enough flow left in the driest month of the year, the legal right to divert some of it, and all of that close enough to where the power is used that the wire run stays reasonable.

Miss any one of the four and the site does not work. A big creek on flat ground has flow without drop. A steep seasonal wash has drop without summer flow. A neighbor's stream is not yours to divert, and in some states even your own stream is not yours to divert without a permit.

None of that costs anything to find out. The first guide below shows how to measure what your water can actually do, with a bucket, a tape measure, and an afternoon. Run the numbers before you spend a dollar.

If your property has no year-round moving water

Then this section is a good read and a poor plan. Solar carries most properties that hydro cannot, and it is already written.

Solar at Property Scale

Why water wins

A small, steady number beats a big, occasional one.

A modest hydro system rarely impresses anyone on paper. Then it runs every hour of every day, and the arithmetic quietly takes over.

It generates around the clock

A 1,000-watt hydro system makes 24,000 watt-hours a day. Matching that with solar at a northern site in December can take fifteen times the nameplate wattage, because panels only work while the sun does, and December does not give them long.

The battery bank shrinks

Solar storage is sized in days of autonomy against a run of dark weather. Hydro storage covers hours of peak use against a source that never stops, so the most expensive part of an off-grid system gets smaller.

The worst month still rules

Streams have seasons the way the sun does. A system is sized against the lowest dependable flow of the year, not the spring melt, which is the same worst-month discipline the solar section runs on.

It is a water system first

The generator is the easy part. Intakes clog with leaves, pipes carry silt, winter makes ice, and the maintenance that keeps a hydro system alive happens at the stream, not at the electrical panel.

What this hub covers

Eight guides, in the order the decisions actually come.

Measure the water, choose the system, choose the machine, build the works, control the power, satisfy the law. The same stream runs through all eight, so the numbers measured in the first guide are the numbers still being spent in the last.

Is your water worth it: measuring head and flow

Two numbers decide everything. How to measure vertical drop and flow rate with simple tools, and the arithmetic that turns them into watts.

Run-of-river micro-hydro

Divert a fraction of the stream, run it down a pipe to a turbine, return it. The standard configuration, and the one most qualifying properties should build.

Small impoundments and micro-dams

Storing water behind a small dam buys power on demand and a set of engineering and permitting obligations that run-of-river never faces.

Waterwheels

Overshot, undershot, and breastshot wheels. Slower and less efficient than a turbine, buildable with ordinary tools, and honest about which trade that is.

Choosing a turbine

Pelton, Turgo, cross-flow, propeller, and pumps run backward. Head and flow pick the machine, and the chart that matches them is most of the decision.

Intake, penstock and winter

Screens that clean themselves, pipe sized so friction does not eat the head, and the freeze protection that keeps a system running through January.

Controlling a hydro system

A hydro generator cannot simply be unplugged. Runaway, water hammer, diversion controllers, and dump loads, which is where the electrical safety lives.

Water rights and permits

Who owns the water, what the state requires before you divert it, and where federal jurisdiction starts. The guide to read before buying anything.

The two numbers

Head, flow, and nothing else.

Head is the vertical distance the water falls between where you take it in and where the turbine sits. Flow is how much water passes per minute. Every hydro decision on every page in this section traces back to those two measurements^[1].

Watts ≈ net head (feet) × flow (gallons per minute) ÷ 10

The Department of Energy's screening arithmetic, with typical system losses already baked into the divisor. It is an estimate for deciding whether to keep going, not a design figure.

Sixty feet of drop and 100 gallons a minute is roughly 600 watts, running day and night. Whether 600 continuous watts covers your household is a question you answer the same way the whole Energy section answers it: from your load list. The Power Needs Calculator works it out from your devices, and the four checks it runs do not change at property scale. Only the numbers do.

Sources

Where these numbers come from.

U.S. Department of Energy, Energy Saver: Microhydropower Systems. System components, turbine and waterwheel types, and the definition of microhydropower as systems up to 100 kilowatts.
U.S. Department of Energy, Energy Saver: Planning a Microhydropower System. Head and flow measurement, the screening power estimate, and the guidance to design against the lowest average flow of the year.
Federal Energy Regulatory Commission, Small/Low-Impact Hydropower Projects. Licensing, exemption, and qualifying conduit pathways for small hydropower, referenced throughout the permits guide.
U.S. Geological Survey, National Water Information System. Streamflow records used to understand seasonal flow variation at gauged sites.