In the video, Elon said that the goal of Tesla's solar roof tiles was to make them as cheap as a conventional roof plus the cost of the electricity they save.
But a couple of days ago he announced that the roof would cost less than a conventional roof even without considering the cost of electricity saved:
He announced that the cost of a Tesla glass tile solar roof would actually be equal to or slightly less than a conventional roof. And no, that is not after deducting the value of the electricity it generates over the next 20 years or so. That is right now, today, as soon as it is installed.
How is that possible? Elon explained to the audience that a lot of it has to do with the current supply chain for roofing materials, which he said is incredibly inefficient. It turns out, the glass tiles weigh up to 80% less than conventional roofing materials, especially ceramic tile or concrete tiles. Both of those are very popular in many locations around the world, especially southern California and the Mediterranean countries. Not only do the Tesla glass tiles weigh less, they are less fragile, which means less loss for breakage.
Much of the cost of conventional roofing materials can be attributed to shipping all that weight over long distances.
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You can see why Elon was excited. As he says, why wouldn't you choose solar roof tiles? They're the same or cheaper than conventional tiles, they're lighter, they're stronger, they look as good or better, and they produce electricity.
Of course, people with existing roofs might not replace them, even if they want solar. But given how beautiful the tiles are, there is probably a very large market, and certainly, it will make a lot of sense to go with solar roof tiles if you're building a new house. Along with the new cheap Powerwall and Powerpack batteries and electric cars and lorries, generation and storage will be transformed.