Electric blankets (along with electric mattress pads, heating pads, and similar) are one option to stay warm when living in your vehicle, but they may have significant electrical demands. As such, they're a great option when connected to shore power or if you have a sufficient batteries and solar panels to handle the load. While using electrical resistance to generate heat is always going to draw a lot of power, electric blankets are a much better solution than space heaters since the area to be heated is small. If you keep the electric blanket under other blankets or inside a sleeping bag, it may not draw much power at all, especially if you can pre-heat your sleeping bag while driving.
Keep in mind that solar panel output is lower in the winter, which is just when you would need electricity for a warming blanket. If you have other options for keeping warm, such as a diesel heater or hot water bottle, those options may be more workable. Your electric blanket should be a 12-volt blanket so you aren't also incurring inverter losses.
A bed warmer is another option that performs the same function as an electric blanket, but with the added benefit of dry heat. They generally do take more electricity than an electric blanket, however. See other contact warming options.
As with any electrical load, make sure you don't drain your vehicle's starter battery. Starter batteries are designed to start vehicles, not power things like appliances or electric warmers.
A blanket that is labeled as washable will most likely have more durable wiring inside, so it will probably last significantly longer.