The idea of solar roof tiles isn´t new. It has been arround for some years now.. I remember seing them on an exhibition over 15 years ago.
All of the companies which made such tiles in germany failed in one way or another, either by changing their focus or by leaving the market.
Here is why:
You need aprox. 15 tiles per square meter. Let´s assume our roof has 60m² per side, so a total of 120m² that would add up to 1800 tiles.
Tesla did not mention how they plan to interconnect all these tiles. Apparently the tiles on the demo houses weren´t connected (the don´t work). The tiles shown did not show any signs of any connector! However these connections are the main problem for such systems:
Electrical Connector resistance
In order to get electricity from these tiles you have to connect them one way or another, preferably with a very low resistance connector, because resistance adds up if you connect resistors in series. A typical MC4 solar connector has a typical series resistance of 0.5mΩ which is fairly low, however you have 1800 of such connectors the total series resistance is 900mΩ or 0.9Ω!
Each and every tile has to be connected to the next one, this is a very time consuming process. If a single connection is broken / bad someone has to check each and every connection over again to find the bad one!
Two cables + connectors have to be soldered to each and every tile they have to be watertight!
Especially the last two points make a solar tile system extremly expensive compared to a standard panel based system. I think the solar tiles are a great way to get a good looking still solar roof, but only if you are ready to pay a premium price for the different look. All other users will stick with default solar panels as they are much cheaper, more efficent and less errorprone due to lower count of connections.