Historically they didn't have a history, but there are "smart grid" electric meters that track energy usage on a smaller time scale, and privacy is an issue for

Historically they didn't have a history, but there are "smart grid" electric meters that track energy usage on a smaller time scale, and privacy is an issue for those. If the lights in your living room total up to 85.5W, someone with access to fine grained power consumption logs can infer when you turned that light switch on or off. Similarly, there's going to be a telltale power consumption profile for when you're in the shower, when you run your washing machine, when you turn on your television, etc. This isn't widespread, but it's something to look out for going forward.