Parking lots have lots of externalities not borne by the parking lot owner. This is an attempt to internalize some of those externalities to make the system more economically efficient. If this causes fewer parking lots to be built the system is more efficient, not less. Marginal parking lots shouldn't be built, only the ones that are truly needed.
OTOH, if a law causes fewer buildings to be built that imposes costs on society. It's harder to argue that a building that becomes infeasible due to the extra upfront costs of solar shouldn't be built.
OTOH, if a law causes fewer buildings to be built that imposes costs on society. It's harder to argue that a building that becomes infeasible due to the extra upfront costs of solar shouldn't be built.