During the 90 or so days of met winter, my heat was on a total of 24 nights, AC ran 11 nights, the remainder of the winter I didn't have to run anything.
Mammoth is hoping to stay open all year - they currently have a 219 - 263" base (which is growing as we speak) but more importantly, there is over 70" of water in the snowpack. It's not going anywhere anytime soon.