Sonoma County airport electric-car-rental plan faces power-supply bottleneck

A plan for electric-vehicle fast chargers at an envisioned new car-rental facility at the Charles M. Schulz–Sonoma County Airport has hit a speed bump: A power provider says it could take several years to provide the large amount of electricity those chargers require.

The facility proposal is being updated for EV rentals to fit with California’s recently accelerated push to electrify transportation to cut emissions.

But a local bottleneck in the electrical grid has the project team exploring ways to lessen the anticipated multi-megawatt power demand from chargers needed to quickly get returned EVs ready for the next renter.

Plans for the consolidated rent-a-car facility have been in motion since late 2019, according to documents presented to the Board of Supervisors early this year. The five rental companies operating at the county-run airport want to increase the number of vehicles available and add joint services such as fueling stations for the fleets, automated car wash and a shop for light maintenance.

But with the state’s plan to phase out sales of gasoline-powered cars by 2035, the project is being adjusted to include car chargers, Airport Manager Jon Stout told the North Bay Business Journal.

Based on a projection that the roughly 500 vehicles in the airport’s rental companies’ fleets would eventually be all EVs, the ConRAC center would need around 10 direct-current fast chargers and over a dozen level 2 quick chargers, Stout said.

Also called level 3 chargers, DC fast chargers provide 3 to 20 miles of driving range per minute of charge. Level 2 chargers give 12 to 80 miles of juice per charging hour.

The fast chargers are desirable because they allow returned rentals to be put back into the available fleet rapidly, Stout said.

“Customers wouldn’t pick up electric vehicles if there’s no charge,” he said.

But DC chargers demand a lot of power — up to 400 kilowatts each — for those fast battery fill-ups. Based on today’s charger and battery technology, the total power demand estimated for the roughly two dozen planned ConRAC chargers was figured to be 5.3 megawatts, largely because of the fast chargers, Stout said.

That total electricity demand is equivalent to what nearly 5,700 West Coast homes consume hourly on average, according to the Energy Information Administration.

But Stout said Pacific Gas & Electric Co. told the project team that its nearest substation just south of the airport wouldn’t be able to supply that level of power demand until unspecified upgrades were completed at least five years from now.

Design and environmental review of the ConRAC project are set to be completed in 14–18 months, with construction planned to start in 18–24 months.

The ConRAC facility isn’t the only airport-area project encountering delays in getting more power supplied.

The builder of several warehouses just east of the airport said PG&E indicated it would take until mid-2024 for upgrades to the same substation and distribution lines to upgrade power at an existing building and serve one currently under construction, the Business Journal previously reported.

A PG&E spokesperson said the utility is working on electric load needs for projects in the airport area, and it’s a challenge the company is facing elsewhere in its service area of Northern and Central California.

“Currently, we are seeing capacity constraints driven primarily by these business sectors: transportation electrification, high-tech campuses and warehousing and delivery centers,” said North Coast spokesperson Megan McFarland in an email. “We understand the real-world impacts that capacity constraints have on our customers, and we are committed to making it right for our customers.”

Upgrades to the substation serving the airport area are estimated to take two to four years to complete once started, because of the complexity of the work required and long lead time on the required materials, McFarland said.

PG&E has spent nearly $1 billion on grid capacity upgrades in the past seven years to try to keep up with electricity demand that has been growing for the past decade after several years of flat demand, she said.

“That said, we know this investment has not been sufficient to meet some current and future needs of some customers,” McFarland said.

So the utility plans to pour $15 billion into expanded capacity and “asset health” over the next decade-plus, she said.

Some of the capacity upgrades have been delayed or rescheduled since 2018 as company funds and workers have been diverted to deal with the threat of wildfire, McFarland said.

California officials have found the utility’s aging equipment and tree-trimming around power lines to be at fault in multiple wildfires in the past several years, namely the 2017 North Bay blazes and the 2018 inferno that leveled much of the town of Paradise.

The Sonoma County airport rental-car facility project team recently submitted to PG&E its power-demand analysis at the utility’s request, Stout said.

“We're starting those discussions with PG&E and what (power) could be served in the beginning, then grow into a full EV fleet,” he said.

One of the options being considered for to lessen the power demand on PG&E for the DC fast chargers is the installation of more solar energy, Stout said.

The sizing of the photovoltaic system with battery storage hasn’t been finalized, but covering the rental and airport long-term parking areas with solar carports could produce around 2 megawatts. That would leave roughly 3 megawatts of total charger demand to be supplied from the grid.

The rental-car facility project follows the opening in November of the new airport terminal, a roughly $40 million project paid for with federal money and airport revenue, and envisioned in the airport’s 2012 master plan. Electrical upgrades for the new terminal were completed in late 2020 and early 2021, before the local supply contraints became an issue, Stout said.

But the ConRAC facility is a public-private partnership between the county and a rent-a-car facility financier selected by the airport’s five current car-rental tenants: Avis, Budget, Enterprise, National and Ace.

The goal is to limit the distance travelers have to walk from the terminal to the vehicles, increase efficiency of storing and servicing the cars, and increase the rental capacity from 192 vehicles currently to 409.

The estimated $36 million project would be funded by rental fees over the 30-year ground lease from the county, according to documents presented to the Board of Supervisors in March. The board approved an increase in the customer facility charge for rentals from $10 total to $5.80 for each of the first five days of each contract, or up to $29 total.

The goal is to open the ConRAC facility in late 2025.

The Board of Supervisors is set to be briefed at a January meeting on challenges in supplying power for the planned EV chargers at the ConRAC center project.

Jeff Quackenbush covers wine, construction and real estate. Before coming to the Business Journal in 1999, he wrote for Bay City News Service in San Francisco. Reach him at or 707-521-4256.

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