Every year, America misses out on 1.2 million megawatt-hours of electricity, enough to power a small city. Where’s it all going? Literally, it’s being flushed down the drain.

With the right kind of technology, we could harvest the energy of water running downhill through America’s infrastructure, including canals, tunnels, pipelines, and existing dams, reports Susan Kraemer at Earth Techling.

The key is “micro-hydropower” devices, which can harvest small amounts of water power. For human-made waterways, there’s Hydrovolts “Big Canal Turbine.”

And for slow-moving streams and rivers there’s the Vortex Induced Vibration for Aquatic Clean Energy converter.

The U.S. Bureau of Reclamation has identified 191 sites in the U.S. on federal property where technologies like these could be deployed, fishing nearly free energy right out of the water.