The solar panels are effectively free, because they will pay for themselves in energy savings long before the building owners have paid off their mortgage/recouped their investment. However, increasing the cost of streetside parking would be actually free (to those that don't own cars) and have a much greater impact on local air quality. Nothing is stopping the city from doing both.
Kind of odd, though - if the panels will so clearly pay for themselves, why did they have to be mandated? Just to be clear, it isn't a purely rhetorical question - I suppose there's a chance that the people who have to pay the upfront costs don't get to realize the savings (buyers don't always factor in the savings, so construction companies may be reluctant to pay for them). Alternatively, people will sometimes just stick with a very inefficient system for a long time, never really getting around to it until they're prompted (by a mandate or tax incentive). Sometimes this is because people are just unable or reluctant to eat large upfront costs, other times it's something they've intended to get around to for a long time but haven't taken the first step.
That said, I do think that if the cost of carbon emissions were genuinely reflected in the price, all these specific technology mandates wouldn't be necessary. I do understand that a single municipality is in no position to make that happen, though.
>The solar panels are effectively free, because they will pay for themselves in energy savings
By that argument, anything with a return on investment is 'free'. The problem here is that you are forcing new homeowners to be forced into investment with a certain ROI that may not be where they want to spend their money. Maybe a family would have benefitted more by using that money to send one of their children to a better school.
