Heating, cooling, and ventilation of commercial structures is up to 80% of their energy costs.
In the USA, up to 80% of residential units and 50% of commercial units, use some sort of ‘Low-E’ (low heat emission) glass. In this particular hardware, the smart darkening process begins the electricity producing magic when the glass becomes a solar cell via a heat driven chemical reaction.
https://electrek.co/2017/11/29/solar-smart-windows-11-percent-efficiency/