The practice of plugging in conventional cars to block heaters -- shown here in Finland -- is still common in some cold climates. (Photo by Suvi Korhonen.)

Cross-posted from Midwest Energy News.

Decades ago, plug-in cars were common in Minnesota.

For cars poorly suited to the upper Midwest’s frigid winters, a block heater plugged in overnight could keep the engine warm enough to start the next morning. Cars and trucks with electrical cords protruding from their grills were a frequent sight.

New technologies such as fuel injection, direct ignition, superior motor oils, and better batteries have largely relegated that custom to history in all but the most frigid regions of the world. But with more than a dozen electric and plug-in car models due on the U.S. market in 2012, some Minnesotans will find themselves reviving the practice.