The Tesla venture into solar roofing shingles is good marketing, but not a revolution. The revolution in rooftop solar is already underway and the most mature solution is still modular panels offset from the roof surface. The reason for this ties into an important concept in engineering and design: beware of a device that claims to do two things at once. In the case of building envelope systems waterproofing is the primary role of roofing materials. A product that can do this reliably and cheaply wins the consumer over. The Tesla roof provides waterproofing protection, but at considerable cost, and because its application defies mass production opportunity, it will be the last choice for most homeowners.