<p>More important than what goes on the walls is what is inside the walls. Heat loss due to poor insulation, and conversely, heat gain in summer is a big factor in energy costs. I used to know a lot of energy conservation professionals, and paint color did not seem to be an issue they talked about. Roof color, yes. Doors, windows, air leaks, big deal. I’d guess, and it is only a guess, that if your wall insulation is poor, this might make more of a difference than if the appropriate R level for your area.</p>