My PGE (Bay area) does the same but I'm pretty sure it's an estimate according to house size, # of people, and a questionnaire I filled out such as "how many times do you run the dishwasher per week". Your house pulls electricity through the breaker box or doesn't.

Then again, it's possible different appliances have a specific electrical signatures like +5KWH x 1.5 hours = dishwasher.