They probably did a ton of work to get those cities aboard but they could have been putting that into getting websites to use darker designs for a pledged amount of time and gotten more energy savings out of it.

CRT monitors, which until a few years ago were the predominant models among PC users, consume more power when a computer screen is white. To confirm this, Schindler measured the energy output of an 18-inch (45.7-centimeter) CRT monitor and found it used 102 watts when the screen was white but only 79 watts when the display was black.

This is not the case, however, with LCD monitors, which have no phosphors and represent the lion's share of every new monitored purchased in the developed world, including those used by laptops. Instead, LCD displays rely on an array of thin-tube fluorescent bulbs that provide a constant source of light to create a white screen. To make it black, LCDs rely on a diffuser to block this light. As a result, LCDs use more energy than CRTs to display a black screen. Measuring a 17-inch (43-centimeter) LCD monitor, Schindler found that white required 22.6 watts, while black came in a tad higher at 23.2 watts. With a 20-inch (50.8-centimeter) LCD, black required 6 percent more energy than white.