I don't even believe this to be true. I've always accepted the typical summer thermostat setting to be 76-78°F and only 66-68°F in the winter time. That's also what the Department of Energy recommends in any official publication I've ever seen.[0] Who are these mythical Americans who leave their thermostat at 74°F forever? [0]http://www.energystar.gov/ia/partners/publications/pubdocs/HeatingCoolingGuide%20FINAL_9-4-09.pdfAmericans tend to keep their thermostats at the same temperature all year around.
See. I find this weird. Up here in Canada, we keep our thermostat about 21°C year round (at least in my experience) with some reductions midday while everyone is out. Insulation is huge, but I don't know if I've ever met someone with A/C, likely because it doesn't really get above 30°C. I imagine it would be similar in the northwestern states.