Solar · Analysis

Solar over the canals: what California's first pilots are testing

Following the Gila River canal-top panels in Arizona, California funded its own pilots over irrigation canals. What the water districts are testing, and the evaporation math behind it.

BY THE RENEWABLE ENERGY LA EDITORS · FILED SEPTEMBER 30, 2026 · 6 MIN READ ·

How solar over a canal actually works

Picture the build: steel supports span the canal, and solar panels sit on them like a carport roof, a few feet above the moving water. The shade cuts evaporation, since less sun on the surface means less water lifting off as vapor. The water returns the favor, because panels run cooler over a canal than over hot ground, and a cooler panel is a slightly more efficient one, though the gain is modest and depends on the day.

Cost is the catch. Mounting panels on open desert land is cheaper than bridging a canal with steel, and the maintenance access is easier. What canal-top solar offers instead is land a water agency already owns, with no new right-of-way to buy or fight over, plus the water saved, and whether those advantages beat the higher build cost is the whole point of running a pilot rather than assuming.

The evaporation math, honestly

The UC Merced study is where the big numbers come from. It estimated that covering roughly 4,000 miles of California's canals could save on the order of 63 billion gallons of water a year and support something like 13 gigawatts of solar capacity (capacity being the maximum a system can produce at once, not what it makes on an average day). Those are headline figures, and this desk would treat them as a ceiling, not a promise.

Here is the honest part. That study is a model, not a measured result, and how much water a real canal loses depends on its width, the wind, the humidity, and how fast the water moves. A narrow canal in a dry, windy stretch loses more, proportionally, than a wide slow one in mild air, and Project Nexus exists precisely to replace the modeled numbers with measured ones. Until it reports, the savings for any given canal are an estimate.

Who is building it, and who pays

Project Nexus is a partnership. The Turlock Irrigation District in the Central Valley owns the canals, the state put in public money (on the order of $20 million at last public report, much of it through the Department of Water Resources), UC Merced handles the research, and a company called Solar AquaGrid coordinates the build. In Arizona, the Gila River project leaned on federal funding through the Bureau of Reclamation, the agency that runs much of the West's water infrastructure.

For the LA basin, the players to watch are the ones that move imported water south. The State Water Project, run by the Department of Water Resources, sends water down the California Aqueduct, and the Metropolitan Water District of Southern California buys much of what the basin drinks. If canal-top solar proves out up north, those are the agencies that would decide whether to try it on the aqueducts that actually feed Los Angeles.

What it means for the basin

Do not expect panels over the California Aqueduct soon. Retrofitting a large, fast-moving aqueduct is a harder engineering job than canopying a district canal, and any power produced still has to plug into the grid, which the California Independent System Operator (the nonprofit that runs most of the state's grid) manages through a slow interconnection queue. The pilots are the cautious first step, not the rollout.

Households have a faster path to LA's sun, and it is still the roof. Canal-top solar is an infrastructure play, one that saves water and makes power at the scale of a water agency, not a home. It is worth following because Southern California's water is imported and exposed, and anything that protects that supply from the heat is a local interest, even when the pilot sits up in Turlock.

Worth watching this month

1. Watch for Project Nexus to publish measured evaporation and power figures from its Turlock canals, the readings that will either confirm or shrink the study's estimates, and the ones that actually matter here.

2. Check the Department of Water Resources and California Energy Commission sites for any move to fund a second, larger canal-top pilot, which would signal the first one is working.

3. Keep an eye on whether the Metropolitan Water District or the State Water Project mentions canal covering in planning documents, a routine paper trail that would still show real interest.

4. Note any Bureau of Reclamation update on the Gila River project's performance, since Arizona's results should arrive ahead of California's.

5. Watch the weather, because a hot, dry Southern California autumn raises both evaporation losses and grid demand, the two problems canal-top solar claims to address at once.

Where this dispatch reads

California Department of Water Resources, State Water Project (state agency, .ca.gov), water.ca.gov/Programs/State-Water-Project, How the state moves water south through the California Aqueduct, the system canal-top solar would eventually have to fit.
California Independent System Operator (grid operator for most of California), www.caiso.com, How new power sources connect to the state grid, including the interconnection queue any canal-top project must enter.
U.S. Bureau of Reclamation (federal agency, .gov), www.usbr.gov, Runs much of the West's water infrastructure and helped fund the Gila River canal-top solar project in Arizona.
Turlock Irrigation District, Project Nexus, www.tid.org, The district hosting California's first canal-top solar pilot, with project scope and status.
Solar AquaGrid (project developer), solaraquagrid.com, Coordinates the Project Nexus build and explains the canal-canopy design and the research goals.
Metropolitan Water District of Southern California (regional water wholesaler), www.mwdh2o.com, Buys and delivers much of the imported water the LA basin drinks, and a likely decision-maker if the idea scales south.

Questions readers have asked

Will this lower my LADWP or water bill?

Not soon. The pilots are small and sit in the Central Valley, not the basin, and any savings would show up first at the water-agency level, not on a household statement. Treat it as infrastructure research, not a rate change.

Why put panels over water instead of on cheaper open land?

The shade cuts evaporation, the water keeps the panels a little cooler and slightly more efficient, and the canal sits on land the water agency already controls. The trade is that building over a canal costs more than mounting panels on open ground.

How much water actually evaporates from a canal?

It depends on the canal's width, the wind, the humidity, and how fast the water moves, so there is no single figure. The pilots are meant to measure real losses on real canals rather than rely on the modeled statewide estimates.

Does covering a canal hurt the water or the canal itself?

Shade tends to slow algae growth, which can help water quality, and that is one thing the pilots are checking. The open question is maintenance access, since crews still need to reach the canal under the panels.