About the Micro-Hydro Output
The Micro-Hydro Power Output Calculator estimates how much electrical power a small-scale hydroelectric setup can generate from a stream or creek, based on water flow rate, vertical drop (head), and overall system efficiency. It's meant for anyone scoping a micro-hydro site, whether an off-grid cabin near a stream or a small farm considering a run-of-river turbine.
How It Works
You enter the water flow rate in liters per second, the head, meaning the vertical drop the water falls before reaching the turbine, in meters, and an overall system efficiency percentage covering turbine, generator, and pipe losses combined. The calculator applies the standard hydro power formula using gravitational acceleration, flow, and head, multiplies by efficiency to get real-world watts, and projects that as a daily kilowatt-hour figure assuming continuous 24-hour operation.
Formula & Methodology
With the default 20 L/s flow, a 10-meter head, and 65% system efficiency, power output is 9.81 x 20 x 10 x 0.65, about 1,275 W. Run continuously for 24 hours, that comes to about 30.6 kWh per day, a figure that stays fairly steady day to day as long as stream flow doesn't change much, unlike solar or wind output.
Examples
Moderate Flow, Moderate Drop
A 20 L/s stream with a 10-meter head and 65% system efficiency produces about 1,275 W, or roughly 30.6 kWh per day if it runs continuously.
Smaller Flow, Steeper Drop
An 8 L/s creek with a 25-meter head and 55% efficiency produces about 1,079 W, or roughly 25.9 kWh per day, showing how a steeper site can rival a higher-flow one.
Advantages
- Applies the standard gravitational hydro power formula directly, giving a physically grounded estimate rather than a rule-of-thumb approximation.
- Lets you compare sites with very different flow and head combinations on equal footing, since both feed into the same formula.
- Projects a daily energy figure that reflects hydro power's key advantage over solar and wind: near-continuous output from a steady water source.
Common Mistakes
- Measuring head as the total elevation drop across a property rather than the actual vertical distance the water falls specifically between the intake and the turbine.
- Assuming turbine efficiency alone represents total system efficiency, when pipe friction losses and generator losses can meaningfully reduce the combined figure below the turbine's own rating.
- Using a single flow measurement taken during a wet period as a year-round figure, when many streams see significant seasonal flow variation that a continuous 24-hour projection doesn't capture.
Edge Cases to Watch For
- Both flow rate and head enter the formula as simple multipliers, so a site with less water but a steeper drop can produce power comparable to one with more water and a gentler slope.
- The 24-hour continuous-operation assumption for daily energy only holds if the water source and system run uninterrupted; seasonal low-flow periods, ice, or maintenance downtime will reduce actual output below this figure.
- Efficiency is entered as a single combined percentage covering turbine, generator, and pipe losses together, so it needs to reflect all three, not just the turbine's own rated efficiency.
Common Use Cases
- Off-grid property owners with a stream or creek assessing whether micro-hydro is viable alongside or instead of solar.
- Small farms or rural cabins scoping a run-of-river turbine installation before requesting a formal site survey.
- Renewable energy students or hobbyists comparing how flow rate and head trade off against each other in hydro power output.