In 2015, Portland put four turbines inside a 42-inch drinking-water pipe; they generated about 900 MWh a year while the city kept delivering water normally

Most cities probably often end up wasting energy without even knowing it. Water flows downhill through large pipes under heavy pressure. Before it finally reaches your faucet, the pressure has to drop. In most cases, valves will simply release the excess pressure. However, Portland, Oregon, found a way to use it instead. According to a project case study published by Lucid Energy, the company that built the system, the Portland Water Bureau installed four 42-inch turbines in a drinking water pipe. By January 2015, they were producing electricity while water flowed to the homes all the time, just as it did before.

A pipe that was already working hard

Water providers install pressure-reducing valves (PRVs) at several points throughout the water distribution network. The valves are meant to reduce pressure to prevent damage to smaller pipes downstream. However, in the process, energy is wasted, which can actually be utilized. Portland installed its turbines just upstream of one such PRV located below Powell Butte Reservoir of the city. The installation let the system do double duty: harvesting energy that the valve would otherwise have wasted, while also easing the pressure load on the valve itself and extending its working life. The turbines are NSF/ANSI Standard 61 certified, which means that there were no effects on water quality and distribution.


Four turbines, no slowdown

Each turbine resembles a large metal ball rather than a normal propeller. It is made of stainless steel and composite material and has blades inside. The case study showed that the four units were spaced at an average of four pipe widths along the pipeline. Together, they pull some 20 psi of pressure from the water flowing through. That is the pressure that the old valve used to waste. Portland didn’t have to build anything new outside the pipe because the turbines sit inside the existing line. The pipe still performs its original task. Now it just has a second job.

The numbers behind the project

The system is rated at 200 kW. It has generated an average of 900 megawatt-hours per year based on the case study. This amount of energy can power around 100 households. During the pilot's initial eight-month stretch of operation, the system ran above 95 percent of the time, a strong early result for a first-of-its-kind installation. Unlike solar or wind power, this type of energy is not weather- or daylight-dependent. Water keeps moving through the pipe continuously rather than stopping, though the exact flow rate still shifts with household demand over the course of a day, so the turbines are able to keep spinning around the clock even as output varies somewhat with that demand.

Financing borrowed from solar and wind

Portland did not pay for this system. The case study notes it was financed by Lucid Energy, with private money, just like a lot of solar and wind farms get financed. The company recovers its investment by selling the power to Portland General Electric. This is under a 20-year power purchase agreement. At the end of those 20 years, the water bureau owns the system and it gets all the things that the system produces afterward. Pipelines for drinking water usually last more than 50 years. So this deal provides the city decades of electricity down the road, at relatively low cost. It was also the first project in the United States at the time to land a 20-year power deal for electricity generated inside a city drinking-water pipe.

A far bigger opportunity, still largely untapped

Portland’s pipe is a small example of a big idea. A 2018 review in the Journal of Environmental Management found that water pipes across the country have a lot of untapped potential for small-scale hydropower. New turbine designs have made adding this kind of power easier and cheaper. There is a lot of potential. A 2022 assessment by Oak Ridge National Laboratory, a federal science lab under the US Department of Energy, estimated that power from existing water pipes, canals and similar structures nationwide could add about 1.41 gigawatts of new capacity. That’s enough to supply power to over 1 million homes. Some of the greatest potential is in hilly western states like Oregon.

Why this quiet fix still matters

There is nothing flashy about a turbine hidden inside a buried pipe and that is really the point. The turbines run without stopping water service. They do not harm fish or wildlife, unlike large dams. They do not need new land or new buildings either. Portland's project showed that cities can generate clean power from existing water infrastructure. Sometimes, a city just needs to stop wasting the energy already running beneath its own streets.