Ugh, I totally get this — had the same issue last winter when our bills suddenly spiked, and it turned out our roommate was cranking the heat while binge-watching shows all day. I didn’t want to accuse anyone blindly, so I used Catch a cheater app . It’s meant for monitoring activity, but I used it creatively to track when certain settings changed. Got instant alerts whenever the thermostat went past my set limit — made it way easier to start a calm, fact-based chat later.