Alternative Fuels In San Diego: The Shift Nobody Expected
Alternative Fuels in San Diego Transport: What's Changing Fast
San Diego's transportation sector is rapidly shifting to alternative fuels like electricity, renewable natural gas, propane autogas, hydrogen, and renewable diesel, driven by the San Diego Metropolitan Transit System (MTS) zero-emission bus program targeting 100% zero-emission fleet by 2040 and the San Diego Regional Clean Cities Coalition's promotion of advanced vehicle technologies. As of May 2026, MTS operates 38 electric buses and two electric paratransit vans, with 12 more electric buses arriving by mid-2026, alongside nearly 100% renewable natural gas (RNG) for its fixed-route buses. This transition has already eliminated all diesel buses by 2021 and added propane fleets since 2016, reducing emissions by millions of pounds annually.
Historical Evolution
The push for alternative fuels in San Diego began with the San Diego Regional Clean Cities Coalition's designation in 1996, fostering partnerships among fleets, fuel providers, and stakeholders to cut petroleum use. By 2005, about 2,000 vehicles ran on biodiesel and natural gas, displacing 94% of targeted gasoline. MTS advanced this in 2016 by deploying 77 propane autogas buses, slashing greenhouse gases by 2 million pounds yearly and saving $5.8 million over their lifecycle, as stated by CEO Paul Jablonski: "MTS has made great strides to reduce its carbon footprint in San Diego over the past decade."
In 2017, MTS launched a Zero Emissions Bus (ZEB) pilot with eight battery-electric buses, leading to board approval of a full transition plan in 2020 ahead of California's 2040 mandate. By 2021, the last diesel buses were retired, replaced by compressed natural gas (CNG) express buses offering 100% particulate matter reduction and 98% NOx cuts, per CEO Sharon Cooney. Recent milestones include 13 new 40-foot electric buses and electric paratransit vans in late 2025 on routes like 3, 929, and 932.
Current Key Initiatives
MTS's ZEB program now mandates 50% zero-emission bus purchases starting 2026, rising to 100% in 2029, with electric buses rotating across routes for performance testing in varied conditions. The agency finalized an $8.5 million overhead gantry charging system at one division, charging 24 buses simultaneously for fleet-wide expansion. Meanwhile, North County Transit District (NCTD) broke ground on a hydrogen fueling station in 2025, set for completion by summer, to deploy hydrogen fuel cell buses on BREEZE routes serving Oceanside to Del Mar.
San Diego International Airport (SAN) uses renewable diesel-reducing emissions up to 75% versus petroleum diesel-in all airside equipment like baggage tugs since 2023, boosting alternative fuel vehicles to 64% of its fleet including electric and propane. The airport's Clean Transportation Plan also converts ground operators to hybrids, electrics, biodiesel, propane, and CNG.
Available Fuel Types
- Electric charging outlets: 6,204 stations county-wide, supporting MTS's expanding EV fleet and public adoption.
- Natural gas (CNG/RNG): 30 stations, fueling nearly all MTS fixed-route buses with renewable biogas for minimal carbon footprint.
- Propane autogas: 17 stations, powering legacy paratransit and minibuses with 71% lower carbon intensity than gasoline.
- Biodiesel (B20+): 79 stations, used in airport equipment and fleets for easy drop-in compatibility.
- Ethanol (E85): 65 stations, available for private flex-fuel vehicles.
- Hydrogen: 1 public station in Mission Valley since 2023, with SANDAG targeting 50 by 2030; NCTD adding more for buses.
Station Infrastructure Table
| Fuel Type | Stations (Public/Private) | Key Users | Emissions Benefit |
|---|---|---|---|
| Electric | 6,204 | MTS buses, public cars | Zero tailpipe emissions |
| Natural Gas | 30 | MTS fleet (RNG) | 98% NOx reduction vs diesel |
| Propane | 17 | Paratransit, minibuses | 2M lbs GHG saved/year |
| Biodiesel B20+ | 79 | Airport equipment | 75%+ reduction |
| Hydrogen | 1 (expanding) | Fuel cell cars/buses | 70% CO2 cut vs diesel |
Environmental and Economic Impacts
These shifts yield massive gains: MTS's propane buses alone cut 13 million pounds of GHG over their life, equivalent to removing 747 cars from roads yearly. Electric and RNG buses further slash particulates by 100% and NOx by 98%, improving air quality in disadvantaged communities prioritized for rollout. Economically, propane saved MTS $750,000 in year one, with potential $2 million annual fuel savings fleet-wide.
"Not only do the new MCI CNG buses offer an improved riding experience for our customers, we get substantially better air quality results from them as well," said Sharon Cooney, MTS CEO.
Steps to Full Transition
- Complete ZEB pilot analysis from 2017-2021, confirming infrastructure needs like charging gantries.
- Retire diesel by 2021; scale electric buses to 50 in 2026 via New Flyer and GILLIG procurements.
- Implement 50% ZEB purchases in 2026, 100% by 2029, hitting 2040 full zero-emission goal.
- Expand hydrogen via NCTD station (summer 2025) and SANDAG's 50-station target by 2030.
- Monitor performance across routes, prioritizing equity in disadvantaged areas.
Future Outlook
By 2026 fall, MTS launches all-electric Rapid 227 with 12 60-foot New Flyer buses, backed by expanded charging. Hydrogen grows with NCTD deployments and statewide goals of 1,000 stations by 2035. Airport renewable diesel expands, while Clean Cities Coalition drives fleet conversions, positioning San Diego as a national leader in sustainable transport reducing GHG by millions of pounds yearly.
Private adoption surges with 6,204 EV chargers, ethanol, and biodiesel options, supported by incentives and infrastructure. Challenges like hydrogen refueling remain, but investments signal rapid change, with MTS's RNG and electric combo proving scalable for urban mobility.
What are the most common questions about Alternative Fuels In San Diego The Shift Nobody Expected?
What Fuels Are Used in MTS Buses?
MTS powers its 40- and 60-foot fixed-route buses almost entirely with renewable biogas (RNG) via CNG, one of the cleanest affordable options, paired with 168 zero-emission light rail cars. Electric buses with 444 kWh batteries provide 140-mile ranges using regenerative braking.
What Fuels Are Used in MTS Buses?
MTS powers its 40- and 60-foot fixed-route buses almost entirely with renewable biogas (RNG) via CNG, one of the cleanest affordable options, paired with 168 zero-emission light rail cars. Electric buses with 444 kWh batteries provide 140-mile ranges using regenerative braking.
How Many Electric Buses Does MTS Have?
As of early 2026, MTS runs 38 electric buses plus two paratransit vans, with 12 more due mid-year and 13 new 40-footers already on select routes.
What Is the Goal for Zero-Emission Buses?
MTS aims for 100% zero-emission fixed-route buses by 2040, accelerated by 2020 board plan with 50% new buys ZEB from 2026.
Are There Hydrogen Stations in San Diego?
Yes, one public hydrogen station opened in Mission Valley in 2023, serving 15,000 statewide fuel cell cars; more planned including NCTD's for buses.