The Harris Ranch Tesla Supercharger in California, the largest in the world, could still be partially powered by a diesel plant, contradicting Tesla's clean energy claims. This was first revealed by investigative journalist Edward Niedermeyer in 2015 and revisited last year. Although Tesla promised to power all its Superchargers with renewable energy by the end of 2021, the reality at the Harris Ranch Supercharger may be different. Despite these revelations, many Tesla owners continue to prefer the convenience and charging infrastructure provided by the company.