Q. "Can I install these tankless water heaters in my attic?"
A. Without seeing all of your plumbing piping, etc. it is difficult for us to answer with a straight "yes" or "no." One must be sure that a possible water siphoning condition can not be created as these fantastic electric tankless water heaters can not have air in the lines. Water siphoning out of any brand of electric tankless water heater might damage the heater or element when the element is on and there is no water (or not enough water) in the lines. Air should not be touching the elements.