Where do you get 40h from? Assuming living in a place that has long hot humid summers and cold winters, thereby needing AC for most of the year, that number should be closer to 100~200.

I live quite frugally otherwise (balking at other numbers in this thread) and $150 per month in climate cost increase for the daytimes sounds perfectly normal to me. During the hot summers I spent twice that when living in an apartment in the big city.

Also consider most people rent and have little ability to impact insulation and efficiency in their homes.