Unless you drive in a neighborhood frequented by millionaires, you may never have seen a car made of carbon-fiber composites, though they have been on the road for more than two decades.

The reason is simple: the models available with carbon-fiber structures are mostly exotic sports machines from makers like Ferrari and Lamborghini that carry price tags well into six figures. The situation will be different next year, when BMW’s electric city car, the i3, goes on sale in the United States — for roughly the price of the company’s 3 Series models, which start at about $33,000.

Carbon fiber’s high strength and low weight make it ideal for applications where the finished product needs to be as light and strong as possible. Jetliners and fighter planes, made in small numbers where the material’s slow and complex production process is not such an impediment, use these composites extensively. Designers of racecars and high-end sports gear turn to carbon for the same properties.

Until recently, however, there was no way that cars with everyday price tags could contain substantial amounts of carbon fiber. Electric vehicles in particular would benefit, as the weight reduction would translate into longer driving distances on each battery charge.