What is is for? I thought it would be to tell us how much energy we have colected on that level, but it just give us no clue. Either change it to a "Total Heat Someone can get" bar that is filled or not depending of how much of that maximum you collected, or add some numbers to it.
Seriously, this is the most useless added feature I've ever seen in a game :P All it does is show you how many more seconds you'll have to wait for your heat to empty, and even that isn't exact.
Agreed: make the bar some theoretical "Maximum" of the most heat you can get from one floor so that you can see how much heat you've actually gained in that floor.