But when it comes to energy use, the escalator is shamefully bad.
A case study from one environmentally-minded motor control manufacturer--The Power Efficiency Corporation--suggested that an escalator operates at a rate of about four to six kilowatts. Multiply that by every hour of every day that the escalators run and you've quite a sum.
From what I can see, the biggest trouble is that escalators don't care if you take the stairs. Unlike elevators, which only come when they're called, escalators run constantly.
Elevators are better, but the characteristics that make them more efficient, like on-demand service to varying heights, also make it difficult to generalize about the energy use. So I cheated and set a rule of thumb according to what I can reasonably expect of myself. I'll take the stairs to the sixth floor (where I work) but the elevator to my friend's apartment (on the tenth floor of his building).
Recent efforts to create variable-speed escalators and efficient elevators that use regenerative breaking give me hope that one day soon I'll get to be guilt-free and lazy again. Until then, I'll work on my calf muscles.
Edit: I messed up on the kilowatt, kilowatt-hour notation up above. Fixed now. Thanks to