The mandate is not exactly straightforward as it reads in the article, or many of the articles out there in fact.
First, this mandate is not a win for customers. Some new home communities and developers in CA already require buyers to buy solar panels on roofs when built. Right now, that’s mostly because it’s profit-focused. So far, with housing demand as high as it has been, developers in desirable areas have been charging almost twice as much for a measly 2-3 kW system. For example, a friend of ours recently moved into a new dev in the Bay Area and they were forced to buy the 3 kW pre-built system for ~$4.50/W. (Or, they could have leased it for an even more outrageous rate).
Look up SunStreet Energy Group. Those are the type of businesses that will profit most from this requirement. And when homeowners find that the original system is insufficient, who will they go to first to add more panels (without having to buy a new system)?
A business like Tesla Energy has very little opportunity to make it onto the roofs of new residential construction from this mandate. (Maybe if they severely underpriced their panels and took a loss to sell into developers).
Also, this CA mandate allows developers, utility companies, local governments, and any other entity, to create a community solar farm (which can be located even on the opposite side of the state) to provide the minimum amount of electricity required for a neighborhood of homes. This mandate doesn’t necessarily require physical panels to be located on the roof.
I don’t see much difference from this requirement and just forcing electricity customers to pay slightly higher rates by buying electricity generation from renewable sources (ie. PG&E Solar Choice or another CCA).
There was definitely lobbying to get this passed, and not just for feel-good sakes of saving the environment.