My municipal water meter transmits readings in the clear on the 915 MHz band. There's a neat program to catch the readings: https://github.com/bemasher/rtlamr
They could also check the physical meter for that, or if they are wardriving for the signal they could likely pick up the presence/lack of WiFi/5G/LTE signals which would probably be even more accurate than power usage.
1. You can sit in a car and read the meters for multiple houses at once, you actually need to trespass to read the physical meter
2. At home devices will still generate traffic, stuff like ring cameras, any laptops that are set to wakeup on network requests, ipads left behind, tons of smart devices. Water meter sounds like less of a hassle.
3. I don’t think most people use 5G or LTE at home, most would use wifi.
4. You could probably convince gullible people into buying a traffic spoofer device that acts as a residential vpn exit node by saying that criminals can detect when you’re on vacation by reading your wifi usage. Like those devices that will turn your TV on while you’re on vacation.