California's Zero-Emission Vehicle sales rules have been a major reason the state's drivers can now choose among two dozen different plug-in electric vehicles on sale today.

Those rules will expand to cover more carmakers in 2018. And the behind-the-scenes jockeying by smaller makers to lessen the impact of the rules has been intense.

Last month, the powerful California Air Resources Board (CARB) released modifications that gave those carmakers a different way to meet the rules--but kept them on the original timetable.

DON'T MISS: Changes To CA Rules May Cut Zero-Emission Vehicle Requirement (Oct 2014)

As noted by industry trade journal Automotive News, the CARB board met on May 18 to respond to requests from five makers for delays in the requirements.

From 2012 through 2017, the ZEV rules applied only to the six top-selling carmakers in the state: Fiat Chrysler, Ford, General Motors, Honda, Nissan, and Toyota.

While the Nissan Leaf is the world's best-selling electric car, the other five makers launched so-called compliance cars: low-volume electric conversions of existing vehicles, built in numbers just high enough to keep them in compliance with the rules.

2012 Toyota RAV4 EV, Newport Beach, California, July 2012

2012 Toyota RAV4 EV, Newport Beach, California, July 2012

Those cars are the Chevrolet Spark EV, Fiat 500e, Ford Focus Electric, Honda Fit EV, and Toyota RAV4 EV--the last two of which are now out of production, having sold enough to meet their goals.

But starting in 2018, the rules both increase the number of vehicles that must be sold and extend them to a new tier of car companies, the so-called Intermediate Vehicle Makers--those with global annual revenue of less than $40 billion.

They are Jaguar Land Rover, Mazda, Mitsubishi, Subaru and Volvo, which collectively had submitted requests to modify the ZEV rules in various ways.

ALSO SEE: CA To Require Zero-Emission Vehicles On Top Of Gas-Mileage Rules (Dec 2011)

Suggestions for changes included delaying the effective date of the rules, reducing the number of vehicles required, and allowing them to meet the rules with plug-in hybrids rather than battery-electric or hydrogen fuel-cell vehicles.

The CARB directors kept the effective dates in place, so the rules will begin to apply to those five carmakers for the 2018 model year.

But the board did allow the smaller makers to use plug-in hybrids to meet the requirements. Of those five makers, three already have plug-in hybrid SUVs in development or on sale.

Mitsubishi Outlander Plug-In Hybrid - UK version

Mitsubishi Outlander Plug-In Hybrid - UK version

Mitsubishi has been selling its Outlander Plug-In Hybrid in Europe and Asia for several years, and an updated version will go on sale in North America as a 2016 model.

Volvo has sold a diesel plug-in hybrid wagon quite successfully in Europe for three years, and its new 2016 XC90 T8 Twin Engine plug-in hybrid SUV goes on sale in the U.S. later this year.

And Jaguar Land Rover already sells two hybrid Range Rover models in Europe, and has been testing plug-in hybrid versions of them for several years.

That leaves Mazda and Subaru, neither of which is known to have current plans for plug-in vehicles.

Each maker, however, has signed a technology sharing deal with hybrid powerhouse Toyota, which will unveil its fourth-generation 2016 Toyota Prius hybrid later this year.

2015 Toyota Prius Plug-In Hybrid

2015 Toyota Prius Plug-In Hybrid

The 2016 Prius will spawn a plug-in hybrid version, as its predecessor did, and that vehicle's powertrain could well find its way into Mazda and Subaru vehicles that will be sold in California (and other "ZEV Rules states") to comply with the revised rules.

Any of the five makers--and the initial six, for that matter--can also meet some or all of the California mandates by purchasing credits from other carmakers, most notably Tesla Motors.

Tesla had argued against the changes, suggesting that the smaller companies shouldn't get a break given their financial resources--an argument perhaps only Tesla, which is even smaller, could make.

2016 Volvo XC90 T8 'Twin Engine' plug-in hybrid, Spain, Feb 2015

2016 Volvo XC90 T8 'Twin Engine' plug-in hybrid, Spain, Feb 2015

Starting in 2018, however, the rules will ramp up the volumes required. From 2012 to 2017, the number of qualifying vehicles were roughly 1 percent of a carmaker's California sales.

In 2018, that number will start to rise by 1 percent a year.


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