How you would beat that power set up for stealth is wire yourself up -- or buy one set up -- a solar kit with a battery.

You figure out the rough amp hours you need, and stealth charge the unit during the day if possible on top of a building or while you are out somewhere etc doing chores.

The solar panels charge the battery.  You bring the battery unit into your space.    Recharge as needed or ideally -- you have one charging when you offput the first one and take it inside to use it.  

Think Goal Zero Yeti 1200 series for one all set up and configured if you want to spend the money 

Never a waste of money to have such anyways, as a prep item for when the power goes down or the grid does even for a few hours which happens to nearly everyone.  

If it is cloud covered out and no solar charge available -- your unit like the Goal Zero or similar if made yourself -- would have to have A/C power to charge it - so again, stealth charging when nobody is around, or plug into an outlet when you are at a friend's or work, or out eating or doing your laundry.  

That sort of thing.  Use low drain appliances and lights etc and just be frugal w your power needs, scale back, etc.