I am curious for educational reasons why the town won’t allow electric. But that’s moot at this point, the owner, the barn is now on their radar. Makes me wonder if they will take exception to even running an "extension: cord. Or any kind of “electric”
I do most “stuff” without asking. Nothing major that is highly visible from the street. I have found due to bureaucratic BS it is easy to ask for “forgiveness” then permission and have to jump through a bunch of BS to get something simple done. . We are turning into a nanny nation.
When I had an off grid cabin i looked into solar but it was and is still a bit too pricey depending on needs. I bought a couple of marine deep cycle 12 volt batteries. They are used on boats to supply power for short term living needs when the boat’s generator is not running. Unlike car batteries they are designed for this purpose, can take and hold a large charge and power drain.
I used low voltage lights, LED lights weren’t really available at the time. These bulbs use even less power and put out great lightning with very little power drain. I used a inexpensive “power inverter”. Which take 12 volt DC and inverts it to 120 AC. I set this up in the early 2000. All of this stuff is much better made and cheaper these days. I could run my TV with Satellite dish/receiver, stereo/music, computer, etc for several days before the batteries needed to be recharged. If I was just running low voltage lights the batts would last a lot longer.
I also had a small generator. But it was noisy, annoying to run a lot, the quiet ones are very pricey. I had a large auto battery charger (around $100±) that I plugged into the genny to charge the batteries. Took about 2 hours depending on how low they were. Very good generators can be had from Harbor Freight on sale for $250-500+. IMO anybody that lives in the country should have a back up generator. Esp those with horses. Just having a genny big enough to run a well pump is god sent when power is out.
My cabin was wire just like any house. The set up worked great and only cost a few $100. Worth checking out RV websites that carry all kinds of stuff for off road living. Off gird solar websites may have some great suggestions also. The cost of all this stuff has dropped considerably in recent years. But even a simple “solar” set up is not cheap. You will still need batteries because when the sun sets so does the power if running directly off of panels.
The hot water heater can be much more problematic. A standard inexpensive residential electric one really needs to be hard wired to the house’s breaker/electric panel. If the code inspector should stop in because they see lights on in the barn they could take exception to this.
IMO gas residential hot water heater would be the way to go. Run off a large propane bottle, at least a 100 pounder depending on needs. Though new ones are “fired” with an electric igniter. Pretty sure the igniter is low voltage an or have battery back up on them. Old style used a pilot light just like stoves.
The portable propane hot water heaters that have been suggested work, but seem to have mixed reviews. There have been threads on them. Easy enough to do a search for “reviews” on them and the best models.
I wonder if the county will take exception to any kind of “lighting”? Would need to know exactly what the rules and regs are to give suggestions on how to get around what they will allow and what they won’t.