Technology
Small hydro
A stream with a drop in height gives energy around the clock. Pico and micro hydro go up to 100 kW; head and flow decide everything.
Price from: 1,300 $ per kW World
How it works
Power: P = 9.81 × Q × H × η, where Q is the flow (m³/s), H is the head (m) and η is the “water → wire” efficiency (about 0.5–0.7 for small hydro). A 10 l/s stream with a 20 m head gives about 1.2 kW around the clock — roughly 28 kWh a day.
Turbines: Pelton — for high head and low flow; cross-flow (Banki) — for medium head, easier to maintain; the Archimedes screw — for a head of 0.1–10 m, and it spares fish.
Pico — up to 5 kW (often off-grid), micro — 5–100 kW, mini — up to 1 MW. Small hydro costs $1,300–8,000 per kW; concrete and earth structures last 30–80 years.
Pros
- Around the clock and in any weather
- A higher capacity factor than solar and wind
- The structures last for decades
Cons
- You need a stream of your own with a head
- Seasons: floods, low water, ice
- Water use permits
- The intake has to be cleared of debris and silt
Sizes and figures
| Power | P = 9.81 × Q × H × η |
|---|---|
| Classes | pico up to 5 kW, micro 5–100 kW, mini up to 1 MW |
| Example | 10 l/s at a 20 m head ≈ 1.2 kW ≈ 28 kWh a day |
| Price | $1,300–8,000 per kW (IRENA, 2010 prices) |
| Maintenance | 1–6% of the cost a year |
Starting prices
Benchmarks with a source and a date. The price for your property comes in the estimate after a site survey.
| What | Price | Source |
|---|---|---|
| Small hydro World | 1,300–8,000 $ per kW | IRENA: Renewable energy cost analysis — hydropower · 06.2012 |
Russia and Vietnam
Russia rarely
Mountain and hill plots with streams. In winter — ice: a sunken intake and an insulated pipeline; the use of the water has to be registered.
Vietnam rarely
The mountainous north is the classic place for a pico hydro on a stream by the house. Rainy-season floods call for a protected intake.
When it is worth it and when it is not
Worth it
- A stream or small river of your own with a drop of a few metres or more
- An off-grid site in the mountains
Not worth it
- Flat land with no head
- The stream dries up in summer or freezes solid in winter
- No right to use the water
Safety and rules
The intake and the pipeline are designed for floods; the generating unit needs protection against overspeed when the load drops (a dump load).
Goes well with
Battery storage
LFP batteries store the daytime sun for the evening and keep the house running during outages. Packs have fallen to $70 per kWh, but a turnkey system is still expensive.
Solar panels
Modules on a roof, a façade or the ground turn light into electricity. The cheapest new electricity in the world — but only by day and with big seasonal swings.
Request for supply and installation
Describe the property — we’ll calculate it and reply, usually within two working days.