The way a washing machine uses power is quite different from, say, a television or a hair dryer. A family of four has quite a different usage "signature" from a home of single.
By analysing the consumption patterns it is possible to get amazingly accurate insight on who is using the power and what that person/family is doing with it.
You may want to take a look at Alan's blog, a researcher in UK that has studied "disaggregated homes", that is ways to separate the various consumption sources in a home by looking at the overall home power use. He showed that it is possible to recognise the telltale signature of each appliance (see also the figure).
Interestingly, but not surprising, there are companies offering a variety of services, with different biz models, to help you understand, as a private citizen or as a company, your usage patterns, like PlotWatt.
These companies can extract from the digital power meter (assuming you can provide them access to it) or from sensors they can place on your power line (and you need to pay for the sensors) data that are processed to identify your appliances signatures. Once that is done they start monitoring the use, discover a highlight patterns providing information on your actual usage in $ disaggregated into the various appliances and can suggest ways to decrease spending. They can even point out that the fridge may be needing a coolant replenishment and that it would be better to call maintenance to decrease power consumption and decrease chances of a motor break down.
All these data, when aggregated into neighbour, cities ... are invaluable in providing hard facts to power utility companies for more efficient production and distribution.
Clearly, this also arises privacy issues that were not existent before. And it would make possible to price "electrons" to stimulate better systemic usage patterns. And this opens up, potentially, a can of worms, something worth exploring in the next post.