I need to replace the 80gallon straight electric heater i have- which is at least 15 year old (since i've owned the house) and has never been drained.. it has two 4500w elements that burn pretty much all the time (one is sunk in junk, no doubt)...

I'm looking at these hybrid systems using heap pump tech to do the trick... they require a drain, but i think i can pull that off.. my concern is space- right now (where the current one is plumbed and has power available) it's in a pantry that is about 6x8 or so- in the back corner... everything i read says these things need space enough to provide the air so the exchange can draw enough heat out... this would pretty much exclude me from using one, but... there is no hvac duct in that pantry, and the attic access is literally right above the current heaters location- in the summer, that pantry is pretty hot- like, at least 15* hotter than the rest of the house.... so.... i'm thinking the 'available heat in the air=space' is moot... but worth mentioning...

do any of y'all have one of these things? if so- what model/make?  how much impact on your juice use per month? 

thanks in advance...