For the hill places that grew up without grid power.

What microhydro actually is

Microhydro converts the gravitational potential of moving water into electricity. The arithmetic is simple: head × flow × efficiency × constant = power. A 200-foot head with 50 gpm flow at 75% turbine efficiency yields about 1.4 kW continuous. That's about as much as a typical Vermont hill house averages year-round. The catch is "continuous" — microhydro produces 24 hours a day, 365 days a year, which is most of the reason it pencils out where solar wouldn't.

Pelton and turgo runners are impulse turbines: a high-velocity water jet strikes a wheel of bucket-shaped vanes. They are efficient (≈80%) for heads of 100 ft and up. Crossflow turbines are better at lower heads with higher flow. We've installed 11 microhydros in our service area since 2014, all of them Pelton or turgo, all on heads between 80 and 320 feet.

What an install includes

• Site assessment. We measure head with a Garmin altimeter and a 200-ft fiberglass tape; we measure flow with a bucket-and-stopwatch in winter (low flow controls the design point) and a calibrated weir if the brook will tolerate one.
• Penstock design. Typically buried HDPE, 2" to 6" diameter, sized to keep head loss under 10% at design flow.
• Intake and screen. A self-cleaning Coanda-effect screen if the brook brings leaf litter; a simpler trash rack if it doesn't.
• Powerhouse. A small insulated shed below the head, housing the runner, the alternator, the rectifier, and a charge controller.
• Battery bank. LFP (lithium iron phosphate) at 48 V nominal, 14 to 28 kWh. We install SimpliPhi or Victron-compatible cells.
• Inverter / charger. Outback Radian or Victron MultiPlus II in the 4–15 kW range. Single-phase split-phase 240V output.
• Diversion load. A resistive water-heating element that absorbs surplus power when the battery is full. The dump load doubles as the house's hot water in summer.
• Generator integration. An inverter-coupled Honda or Kohler genset for the once-a-year week when the brook is frozen and the sun is gone. ATS handled by the inverter's AC2 input.
• Run from powerhouse to house. Direct-buried URD aluminum, sized for < 2% loss at full inverter output. Typically 4/0 if the run is over 200 ft.
• Disconnects, OCPD, and bonding to NEC 690 (PV) and 705 (interconnection) as applicable.
• Engineering stamp on systems > 5 kW. Subcontracted to a VT-licensed PE.

What's hard about it

The hardest single part of a microhydro install is the penstock — not the electrical. A 200-foot head over 600 feet of brook means 600 linear feet of trenching through what is usually rocky soil with tree roots, often across two property boundaries, often through a wetland regulated by the Vermont Agency of Natural Resources. We do not dig the trench; we coordinate with whoever does (a local excavator, usually a customer's neighbor with a CAT 305).

The second-hardest part is keeping the runner alive in winter. Vermont brooks ice up; intake screens freeze; nozzles freeze. The standard mitigation is to size the design point at the December low-flow, run a slow-trickle bypass at the intake, and accept a 5-week winter shutdown if it's a hard year.

Off-grid solar

For sites without a usable head, off-grid PV with battery is the alternative. We design with NREL PVWatts for the production estimate and target 4 days of autonomy in the worst-case month (December, locally — about 1.6 kWh/m²/day). A typical Vermont off-grid system: 6–12 kW PV array, 20–40 kWh LFP battery, Outback or Victron 8 kW inverter, 10 kW propane standby, all integrated.

What's not included

• Trenching for penstock or PV-to-house conduit. Subcontracted.
• Wetlands permitting if the penstock crosses a regulated wetland. We refer to a wetlands consultant.
• Genset (the unit itself). We wire to it; the customer buys it.
• Wood-stove or propane backup heating. We provide the electrical for whatever heat-source the customer chooses.

Price band

System	Typical low	Typical median	Typical high
Microhydro 1–3 kW	$22,000	$36,500	$58,000
Off-grid PV 6–12 kW	$32,000	$48,000	$72,000
Hybrid (hydro + PV + genset)	$48,000	$68,000	$95,000
Battery-only retrofit (existing PV)	$14,500	$22,000	$34,000

Related

For a worked example, see Walden microhydro install — 1.8 kW Pelton on a 220-foot head.