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.