Do you strictly have to deprive others of content to be stealing? Taking away potential revenue, stealing someone’s design, etc. are also forms of stealing. If a gaming company lifts some art someone shared and put it in their game without compensating the artist or getting permission, would that not be stealing? They’re not taking away that content from anyone else - so is that ok?
All space heaters operate at the same efficiency since they convert electricity to heat via resistance. You may have a small one and low electricity rates in your area to see a negligible change. Or maybe other uses went down and masked the increase from the space heater usage.