The cost of the solar panels doesn't necessarily come out of the buyer's pocket. Instead, the cost could come out of the previous landowner's profits, if prices are mostly determined by what buyers can afford. In other words, the land drops in value by the cost of the solar panels that will have to be installed on it.
Transportation across single-family-home sprawl, which we explicitly cultivate with regulation, is a far greater contributor to climate change than utility power.