Fistful, you ain't done with the habaneros until they're done with you.
You'll know that as they come out the other end.
Regarding heats of a given chili variety, you have to consider the circumstances.
I grew a whole bunch of jalapenos this year, along with poblanos, fajita bells, and a new variety called a chenzo.
My jalapenos were quite mild, but the chenzos packed a whallop. The fajita bells took a turn for the warm side, too.
One of my workmates brought in a big selection of jalapenos that dwarfed what I'd seen from my garden and local grocery stores.
I took those home, roasted them, blanched them, skinned and cleaned them, and stuffed them with monterey jack cheese before breading and deep frying.
Oh. My. Goodness. They were unbelievably hot for a jalapeno. I've had habaneros that delivered less fire.
Turns out this summer's drought and high temperatures added an extra element of heat to a lot of the garden chilis grown in this neck of the woods.