Human body power consumption in still state
You're basically correct.  I don't know if you've found the Wikipedia article on Basal Metabolic Rate but it's got everything you need, including a bunch of formulas you can use to figure out an average value for a given body type.  There are also many online calculators, such as this one.  You can easily figure out averages, which I think is what you want, but between two individuals the number can change quite a bit.

Why does 80 watts sound so low?  This is more of a physics.se answer, but Watts are a unit of power which mean they measure energy use over time; W=J/s, or Joules per second.  Every second.  Have you ever touched a 75 watt lightbulb?  They're hot as hell.  If your human does nothing all day, s/he will be like an inefficient incandescent lightbulb on for a full 24 hours.  Maybe that seems low but electricity is relatively cheap these days.  To use another classic physics experiment, 1700kcal=7000kJ=a lot of ice turned into steam.

No wonder my father always made me turn the light off in the bathroom...