Car buyers don't have to live under California's golden sunshine to want electric cars. Yet, in some months, buyers in California purchase more than half of all the electric cars sold in the U.S.

According to reader Mike Kamm (H/T Mike), even several of the electric cars that used to be sold in the Northeast are now nearly impossible to find on dealers' lots, at least in his home state of New York. New York is one of nine Northeastern states that have signed on to California's Zero Emissions Vehicle (ZEV) program. Among the cars he says he can no longer find at dealerships are the VW e-Golf, Smart Electric Drive (that is, any Smart), and BMW i3.

Green Car Reports has confirmed with Hyundai that its two newest electric cars, the Ioniq Electric and the Kona Electric will only be sold in California. Subaru's new plug-in Crosstrek Hybrid may be limited to the Golden State too.

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This was the year all of that was supposed to change, as the arcane "travel provision" of California's ZEV program expired, preventing automakers from counting electric cars sold in California toward requirements in other states. 

So what gives?

We asked Simon Mui, senior scientist and director for California vehicles and fuels with the Natural Resources Defense Council for his take on why more electric cars aren't showing up outside of California despite the expiration of the travel provision.

READ THIS: Why Electric Cars Are Rare Outside CA: Arcane 'Travel Provision' Rule

The short answer is that the six largest automakers, those that are subject to the ZEV provision, have already amassed enough credits in every state under the travel provision to carry them into next year or beyond before they have to worry about selling cars outside California. Even some intermediate-size automakers, such as Hyundai, which have lower requirements and can rely more on plug-in hybrid models than pure electrics to meet their mandates, have built up enough credits under the travel provision that they won't have to sell cars outside the state for years.

Tesla also sells credits that it earns but doesn't need, which gives some automakers another way to avoid building many electric cars at all.

Since cars are large, heavy, and expensive to ship, automakers concentrate their distribution in certain regions. And since California has the most established electric car market—along with favorable weather and more buyers already educated about electric-vehicles—it makes economic sense for them to concentrate their sales on the West Coast.

CHECK OUT: California bought more electric cars than rest of U.S. combined in June (2016)

Mui confirms Kamm's observation that most electric cars are not available outside California. Of the 41 plug-in models sold in California, he says only 25 are available in Colorado, a non-ZEV state, but the one with the highest purchase incentives of any state.

Other regions, such as the Northeast and the Rocky Mountain West, have also been traditional hotbeds of interest in SUVs, crossover vehicles, and other all-wheel-drive models. So far, few SUVs or crossovers have been offered as electric models but that is starting to change.

With more electric crossovers and SUVs coming on the market, ZEV credit requirements ramping up, and the expiration of the travel provision, Mui expects that 2019 will be the year more electric cars will become available outside California.