Originally Posted by DilceFarNiente
Pretty sure all modern RV tanks (bays) are heated by warm furnace air and not each tank individually by electricity, and I suspect the wires you are seeing are the level indicators.
Certainly true in my 1997 38' Sunvoyager DP.
Back in the 90's, I'd say many did not come with that option standard. Gulfstream had that Alaska option (I think they called it) which the original owner of our Coach added.
I'm sure in the last 18 years it's probably a common standard feature.