I swear that not having to pay for the air conditioning must be one of the best parts of staying in a hotel when on vacation or traveling in the summer heat. I take every chance I can when traveling to those ancient AC units up full blast and eke out every penny's worth of my hotel room rate. They might sound like a freight train, but man do they get the job done. If you fall asleep with them on, without fail, you wake up crogenically frozen in the middle of the night.
Anyway, you have to imagine that that's what this neighbor was doing, knowing that they weren't paying for their AC costs, and that their neighbor's unwitting tenant was going to be footing the bill for them. Literally coasting through the latest heatwave while the tenant was sweating it out next door and none the wiser. Still, if you went through all that effort to wire your AC unit to your neighbor's electrical circuit, you think you'd be subtle about the usage of it so that they didn't immediately figure it out.