Cut waste, create jobs, save money — what’s not to like?

There is a link to several ideas to put people back to work, but the focus is on painting rooftops white to save utility costs, and idea that was popularized by Steven Chu, the Secretary of Energy.

There’s a claim raised in the comments:

AC costs less than heating

Obviously the total amount you spend on heating and cooling will depend on the climate where you live, but what if we quantify this? A degree of heating vs a degree of cooling? Then it becomes easy to make a comparison to see how compelling rooftop painting might be — if you have comparable degree-days of each, then whichever is cheaper tells you which way to go.

The basic argument is a simple application of thermodynamics. All nonreversible thermodynamic processes (which include your heating and air conditioning) reject heat. In the case of heating, though, the goal is to produce the heat, which means you can build heaters which are basically 100% effective. Cooling, however, has to reject heat, and becomes less efficient as it becomes hotter outside. Cooling efficiency is necessarily less than 100%, which means cooling an arbitrary mass by a degree costs you more in energy than heating it does.

Then there is an economic analysis — are you using the same energy source for cooling and heating (say, gas heating vs electricity for cooling) and are those energy sources costing you the same, and how much heating and cooling do you do? If you live in a dry area you can use a swamp cooler, which is probably relatively cheap. But make no mistake — the energy to cool by a degree is greater than the energy to heat by a degree.