Hey Mr. Green,

Is it better to convert an old gasoline car to electric rather than replace it, if one can afford the conversion price? I'm hoping this might be an environmentally friendly option for drivers like me who have a vehicle they would like to keep for a long time.

—Cooper in Davis, California

A lot depends on what kind of car you drive. Many vehicles are more than 4,000 pounds, while some weigh in at less than half that much. If it’s up there in the two-ton range, it may not be worth the effort. That’s because it takes much more power to propel a heavier vehicle, while lighter weights like a Chevrolet’s Metro (1,653 pounds) or Aveo (2,315 pounds) may be valid candidates. It’s worth noting that cars have expanded over the years. The successor to the Aveo, the Sonic, is now up to 2,794 pounds.

Costs and labor for the electric retrofit vary, from anywhere between $5,000 and $20,000, depending on how many steps are required for the vehicle, from removing the engine, gas tank, exhaust system, and clutch to rewiring the ignition switch. One source, Project ForenSwift, claims to have spent a net of only $1,000 on electrifying a used Metro that originally cost $175. The owner had to scrounge used parts and did not reveal how many hours they dedicated to the project.