Lowtech Graph lists low-tech options for every need of a home. Here you can compare them, find tutorials to build them, and link them together into a circular system. Why low-tech?
Water motor for direct mechanical drive
Passive
One of 8 ways to meet this need. Cost, carbon, footprint and rankings are relative to other solutions for the same need, not absolute.
What your site needs
A watercourse with usable flow and fall, close to where the work is done
A water wheel in a stream whose turning shaft drives a machine directly: a pump, a mill, a washing drum or a workshop tool. There is no conversion to electricity and back, so nothing is lost on the way and there are no electronics. The work is done for free, but only where and while the water runs.
Long; bearings and the runner are the wearing parts and both are replaceable
Embodied carbon
Low
Space / material use
Medium
Output timing
Continuous process
Skill to repair
Intermediate
Regulation (FR example)
Works in and abstraction from a watercourse are regulated; a declaration or authorisation is normally required, and rights on non-domanial watercourses vary.
Levels are relative to the other options for this need, not absolute. Fewer dots is lighter.
Water motor for direct mechanical drive (This page) Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Low · Skill to build: Intermediate · Upkeep: Regular · Change to daily life: Occasional · Works without the grid: Yes Choose it if you have a stream and want it to drive a pump, a mill or a tool directly, with no electronics.
Solar PV array Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Medium · Skill to build: Intermediate · Upkeep: Light · Change to daily life: None · Works without the grid: Yes Choose it if you have a sunny roof or patch of ground and want free electricity with no moving parts.
Small wind turbine Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Medium · Skill to build: Intermediate · Upkeep: Regular · Change to daily life: None · Works without the grid: Yes Choose it if your site has steady wind and you want power at night and in winter.
Micro-hydro turbine Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Medium · Skill to build: Intermediate · Upkeep: Regular · Change to daily life: None · Works without the grid: Yes Choose it if water flows all year on or next to your land and you want power day and night.
Mains electricity Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Low · Skill to build: Specialist · Upkeep: None · Change to daily life: None · Works without the grid: No Choose it if the grid reaches you and you want the most reliable supply in normal times.
Pedal / hand-crank generator Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Low · Skill to build: Basic · Upkeep: Light · Change to daily life: Daily · Works without the grid: Yes Choose it if you want a little emergency power, for a phone, a light or a radio, from your own muscles.
Electric motor (mains or battery driven) Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Low · Skill to build: None · Upkeep: None · Change to daily life: None · Works without the grid: No Choose it if you want quiet, controllable drive at the flick of a switch.
Small petrol or diesel engine (direct drive) Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Medium · Skill to build: None · Upkeep: Heavy · Change to daily life: Occasional · Works without the grid: No Choose it if you need heavy work done far from any wiring, even when the grid is down.
We don’t list sizing or quantities, as the yield of each technique depends on the quality of its build. The catalogue compares options but doesn’t dimension them. Regulatory notes are indicative, with a French example, and need to be confirmed locally.