In Australia banks will not be allowed to finance gas powered cars only battery powered cars.

I bet your rentals have had their smoke detector batteries changed more often that your home. 

I had two occasions where the tenants looked amazing on paper, and connected with them really well during showing but turned out to be super incompetent tenant and called me about everything inconvenient about the house (i.e. smoke detector out of battery, spots with wall paint, natural porous holes on a travertine floor tile).  

The ADU would run off the solar batteries and if necessary pull electricity from the main house.Is this a viable solution? 

Not changing filters, door locks, leaky faucets, shower heads, smoke alarm batteries, and not doing touch up paint/cleaning. 

It has never failed or need batteries replaced.I do use wifi thermostats, wifi water heater and exterior cameras.

There is internet and a fully charged battery... and you eagerly do a search for, "what bait should I use to catch Tuna?"

They recently launched battery operated cameras and flood light cameras to better compete with Ring.

A local to me property just came on the market with a Tesla roof and battery wall. 

However, if you installed a complicated thermostat that is difficult for the average user to operate without a manual, then you should bare some responsibility.Can they just unplug it, remove the battery, and wipe the memory?