I am in the process of installing a natural gas-powered outside tankless water heater. It's a small house, so I want it installed on an exterior wall to save space inside. The issue I'm running into is clearances around the heater. I have a very small spot where it can be installed on the back of the house, and in order to meet the 12" away-from-a-window requirement, I would need to mount it right next to my main electrical service panel (and electric meter). I have found no code requirements about mounting next to an electrical panel. All breakers are enclosed in the panel and the wiring is all enclosed in conduit, so I'm not sure this would be a problem. The only thing I found refers to the gas meter itself, which must not be installed within 3 feet of an electrical panel. That's fine, as my gas meter is on the other side of the house. I guess the code by which I should abide is for 3/4" gas lines themselves, if any code exists for running them in close proximity to electrical panels. That's the only thing I can think of!