California's appliance efficiency regulations (Title 20) are much stricter than to anywhere else in the US, as far as I know. http://www.energy.ca.gov/appliances/
The effects are felt elsewhere, too. Most manufacturers aren't going to design two versions of a model for two regions, the energy efficient one, and the less energy efficient one. They'll just work to make one that fits the more stringent one. California has been one of the biggest drivers of EE nationwide because of that.
It's interesting to see it in practice too; if you move to California and bring a car, part of the registration process is to check the car and make sure it indicates it meets California requirements in design and build (not just smog testing; they do that too, but the actual registration/titling will involve them popping the hood and checking the car has the right markings). And basically every modern car does.
CARB is basically the EPA now. They're the ones that prosecuted Dieselgate, as they're the only regulator who put the screws to VW once they realized what was going on.
The federal government is trying to take away California's right to set their own vehicle standards. Is anything similar happening with these other energy efficiency standards? I believe there were moves to roll these back too at a federal level, eg trying to kill Energy Star:
Title 24 itself is broken into 16 climate zones [1], each comes with its' own table of acceptable parameters. The deviation in parameters allows for a wide range of equipment at varying standards.