They really can be enlightening such as teaching just how much it costs for those little lights on various items that are on to show that they have power to them.I think I'm going to actually have to buy one of those things that Elk mentioned to measure how much electricity something uses.
I used mine specifically to learn how much it costs to run my 40 year old refrigerator vs the advertised cost for a new refrigerator. I also learned it costs me $5 a month to run the fan in my greenhouse and $5 a month to run the fluorescent light over my plants in the living room. I should measure that again since it has a new ballast and supposedly LED bulbs.
It will not work on 220V or I would have measured my hot water heater and my well pump.