"Cities and their expansive hardscapes are certainly to blame for the heat island effect and, since the hardscapes and solar energy-absorbing roofs are already there, solar panels may actually represent a reduction in heat absorbtion. Add to that the fact that solar panels produce renewable energy that does not contribute to climate change like conventional sources like coal. Adding to that, the soot particles in the atmosphere from the burning of fossil fuels contribute a radiative forcing of 0.1 to 0.4 W/m2. Solar panels, on the other hand, are reducing the amount of climate change-causing emissions.

"So if you're wondering about the heat island effect before installing rooftop solar, don't. According to the numbers, the solar panels will not only produce energy, but keep your home slightly cooler, which means you'll be using less energy in the first place, which will keep us all a little cooler."

Haven't done any math either ways, but it's not like sunlight doesn't already heat up the planet.