Clean Energy SF: San Francisco, fog then sun, est. 2026

Vol. 1 - No. 14 - Thursday, September 24, 2026 - Free to readers

Wind ยท Analysis

Altamont Pass: trading thousands of old turbines for a few tall ones

San Francisco's oldest regional wind resource is trading thousands of small 1980s turbines for a few tall ones. The swap is a bet that more height and slower blades mean more power and fewer dead eagles.

Filed October 22, 2026 By the Clean Energy SF editors Reading time: 6 minutes

I. How the swap changes the pass

Altamont's original turbines were rated at roughly 100 kilowatts or less each, hundreds upon hundreds of them strung along ridgelines on open lattice towers that looked like radio masts and gave perching hawks a place to sit right in the blade zone. At its peak the pass held something on the order of several thousand of these small machines. A repowered turbine is a different animal: rated in the low megawatts, often around 2 to 3 megawatts apiece at last public report, set on a smooth monopole well over a hundred feet tall, with blades that sweep a wide circle but turn at far fewer revolutions per minute.

One new turbine can replace dozens of old ones and still produce more power. Fewer towers mean fewer obstacles in the flyway, slower blade tips give a bird a better chance to see and avoid them, and taller hubs lift most of the sweep above the height where raptors do most of their hunting. None of that is automatic, which is why the permits that allow the new turbines also require years of counting carcasses.

II. The eagle math nobody can round off

Golden eagles are the reason Altamont is famous and the reason repowering took so long to settle. The old field was estimated to kill a meaningful number of golden eagles a year, a figure that operators, conservation groups, and wildlife agencies argued over for years, because eagles are long-lived, slow to breed, and genuinely hard to count. Do not trust a precise annual eagle number from this pass; the honest version is that mortality ran high enough to worry biologists about the regional population, and cutting it was the whole point of the deal.

Monitoring since repowering has generally pointed toward fewer bird deaths for each unit of energy produced, though the findings carry caveats: methods changed, some new turbines stand in different spots than the old ones, and a few years of data cannot settle a question about a bird that lives for decades. This is a case where 'it depends' is the truthful answer, and what it depends on is more counting, done by independent monitors and filed where the public can read it.

III. Who holds the permits, and where your power fits

Alameda County is the lead local permitting authority for most of the Altamont, and its conditional use permits (the county approvals that set how many turbines, where, and under what wildlife conditions) are the documents that actually govern repowering. The California Energy Commission keeps records on the state's power plants and has tracked Altamont facilities for decades. NextEra Energy Resources operates a large share of the modern turbines, with other developers holding the rest, and ownership has changed hands repeatedly since the 1980s, so the name on a given row of towers may not be the one you recall.

For a reader in San Francisco, the link runs through procurement, not geography. CleanPowerSF and other community choice programs buy renewable power from across the region, and regional wind sits in that pool even when no single turbine is labeled as the city's. To see the renewable share behind your account, the Power Content Label (the annual disclosure California requires every power seller to publish) is the document to ask for, not a turbine on a hill.

IV. Worth watching this month

1. Alameda County planning filings for any remaining Altamont repowering phases, routine until a phase proposes new turbine locations, at which point the wildlife conditions get re-argued.

2. California Energy Commission records on Altamont facilities, worth a glance when annual generation or capacity figures are refreshed, usually a quiet housekeeping update.

3. Published avian monitoring reports for the pass, the item that actually matters here, since they are the only public measure of whether the bird bet is working.

4. Any permit renewal or settlement touching golden eagle take authorization, which is where the real arguments happen and rarely a routine matter.

5. The SFPUC's annual CleanPowerSF Power Content Label, a routine fall publication showing the renewable mix behind city accounts.

Frequently asked questions

Does any of my CleanPowerSF power come from Altamont?

Possibly, but no one can trace a single turbine to one meter. Community choice programs buy renewable power across the region, and Altamont wind is part of the broader Bay Area supply. The Power Content Label shows the mix, not the map.

Did repowering really cut bird deaths?

Early monitoring generally points that way, but the data is still thin and the birds involved live a long time. The fair answer is that it looks better and needs years more counting to confirm.

How many turbines are out there now?

Far fewer than at the peak. The old pass held several thousand small machines at last public count; repowering has replaced most with a much smaller number of large ones. Current figures live in county filings.

Why did this take decades?

Negotiating the wildlife terms, especially golden eagle protections, was slow and contested, and old turbines came down in phases rather than all at once. Permits, lawsuits, and monitoring agreements all stretched the timeline.

References