Most of the sunlight that hits a roof is already turned into heat. Whether you use that for calculations or not does not make a difference. Not sure about the

Most of the sunlight that hits a roof is already turned into heat. Whether you use that for calculations or not does not make a difference. Not sure about the exact numbers, but I guess that at the moment normal roofs and solar panels absorb very roughly about the same percentage of sunlight. So if in the future solar panels become more efficient, then yes, the amount of sunlight turned into heat could double. Maybe that can be offset by covering other parts of earth with reflective materials or finding a way to send the heat back into the universe more effectively.