Aunti, they're probably just trying to cut their electric bill,figuring you can heat your own water..RV style ...on your buck...
We don't go to campgrounds anyway...so it matters little what silly restrictions they have ... Our mission is SOLELY about hurricane EVAC...sitting in a friends backyard/driveway elsewhere, connected to their 110V AC power...awaiting the word that it's OK to go home ...Electric or Solar Water heaters suit me just fine ...
During Katrina , the other displaced million people were scrambling to find propane which was in short supply, you had to drive a long ways to find it , only to find a line longer than your patience...... electricity was plentiful...anywhere out of the direct storm area...
Many here seem to keep applying "social " camping parameters here, which don't apply in this situation...Having been an storm evacuee for most of my 60 years, (yearly Hurricane risk)we've developed a sense of exactly what we need to survive living /evacuating in these storm ridden zones...
Even before TTTs and TDs , every year we'd assemble our containers of "stuff" (house papers, family photos, sentimental objects d'art, canned food, clothes , a few handmade guitars , the "royal' needs : ), anything that just HAD to go...so we're well practiced at "getting outta' Dodge"....
The small electric WHs would be all we need for the wife and I... we're getting Old so we're never in a rush to do anything ...
The wife keeps leaning towards the "Hot Rod" idea(I did request her input) as being a cheap alternative ,and allowing us to retain the propane WH , in case we sell the trailer in the future. (her words)...as I read the Atwood manual , I see similar heating elements in their P/E WHs...typically ,I guess it's OK as long as you use their products exclusively...