My smart gas meter produces one data point per day in units of whole therms. Usage for the last few days looks like this:
1, 2, 3, 1, 1, 2, 1, 0, 1, 1, 1, 2, 3
Good luck doing the data analysis on that to tell what time I take a shower.
If I had a smart meter for electricity (I don't, PG&E won't give me one because I have solar panels on my roof) there might be more of a problem as I understand that these provide per-hour data - not sure of the resolution. I'm certain that you'd be able to tell when I run the clothes drier - but smaller appliances are going to be difficult to spot in hourly data.