Some manufacturers only offer their plug-in hybrid models in certain markets, even as hybrid models are now generally offered nationwide.
Like electric cars, plug-in hybrid sales are sometimes limited to markets deemed suitably friendly to these types of vehicles by their makers.
But Hyundai has a more ambitious strategy.
DON'T MISS: 2017 Hyundai Ioniq preview
It will offer its Sonata Plug-In Hybrid mid-size sedan and Ioniq Plug-In Hybrid everywhere in the U.S.—although a special order may be required in some states.
The Sonata Plug-In Hybrid was introduced in 2015 as a 2016 model, and Hyundai is just now beginning to roll out the Ioniq as a 2017 model.
The Ioniq Plug-In Hybrid will only be actively marketed in the 10 states that share California's emissions standards, but it can be ordered in all 50 states, a source familiar with the matter said.
In addition to the plug-in hybrid model, Hyundai will offer hybrid and battery-electric versions of the Ioniq.
The hatchback is Hyundai's first dedicated green car, intended to rival the Toyota Prius, plug-in hybrids like the Ford C-Max and Chevrolet Volt, and mass-market battery-electric cars like the Nissan Leaf.
It uses a body structure derived from the Elantra compact sedan, but with model-specific styling and modifications to accommodate the different powertrains.
The plug-in hybrid version uses the same 1.6-liter 4-cylinder engine and 6-speed dual-clutch transmission as the hybrid model, but with a more powerful electric motor and a larger lithium-ion battery pack than that version.
The 8.9-kWh pack provides enough capacity for about 25 miles of electric-only driving, according to Hyundai.
While the Ioniq is a dedicated model, the Sonata Plug-In Hybrid is a plug-in version of Hyundai's bread-and-butter mid-size sedan.
2017 Hyundai Ioniq
It uses a powertrain derived from the Sonata Hybrid, including a 2.0-liter 4-cylinder engine, 6-speed automatic transmission, and an electric motor.
But its 9.8-kWh battery pack is much larger than the Sonata Hybrid's 1.6-kWh, allowing for an EPA-rated electric range of 27 miles.
Both models are part of Hyundai's plan to—along with subsidiary Kia—become the second-biggest seller of green cars worldwide, after Toyota.
That plan involves the launch of multiple hybrid, plug-in hybrid, and battery-electric models across both brands, as well as continued development of hydrogen fuel-cell vehicles.