He also warned this will hurt earnings in the short term.

In a note on Tesla's blog posted Friday afternoon, Musk says the Model S will now have an 8-year, "infinite-mile" warranty that will also apply retroactively.

"In hindsight, this should have been our policy from the beginning of the Model S program," he writes. "If we truly believe that electric motors are fundamentally more reliable than gasoline engines, with far fewer moving parts and no oily residue or combustion byproducts to gum up the works, then our warranty policy should reflect that."

But this will likely mean Tesla will require more reserves to address issues covered by the warranty, meaning lower profit margins.