Oddly enough, household energy consumption is often stated in kWh/year. Being that hours per year is a bit under 10,000 one can convert this kWh/year ridiculousness onto simple W, and the resulting amount is only one order of magnitude different. But I guess it helps people annualize their their electric bill (monthly statements being in kWh) without much math.
In the course of doing some energy improvements (and considering various options), I used the rule of the thumb that 1W continuous costs $2/yr, which was more than close enough mathematically, surely made the math easier to do in my head, and was in the units of the actual tradeoff that I was making (buy an efficiency improvement for $Y, save $Z/yr).
