maybe over the lifetime of the installation ? But then they say the battery must be replaced after 5 years... So 5*12 - 30 months = 30 months without paying. So one pays about half 2.17 per day over the 5 years. But that's still about 5 times more than 0.21$/day... I'd love to believe the article, but you're right, the maths seem wrong.

That's in a "bear case" section and honestly is far too bearish, warranties are typically 10+ years for. Unless you buy something super cheap that goes bad and the manufacturer is no longer around.