We have a house member who does not understand the effect on our electric bill of running his TV and space heater when not really using or needing them. We need proof of how much power he consumes.
Is there a meter that can be plugged into an outlet that shows the KWHs used over a period?
If not, some environmentalist geek might want to invent one.

Get a watt hour meter like the kill-a-watt. It'll tell you the watts per hour being used. And you should be able to find out how much electricity costs usually in kWh's (on your electricity bill), and do the math. I don't know if I'm aloud to link to a commercial site, but here it is...

Kill A Watt P4400 (http://www.smarthome.com/9034.html)

EDIT: The big power hog will be the space heater. They can run upwards of 1500 watts, which is 1.5 kWh's. Where I come from my utility charges $0.0594 per kWh. So if you run a space heater like that full blast for 24 hours per day, it'll cost me $2.14 per day or $66 per month give or take. That is a lot per month, even at half the power I wouldn't want that on my bill. And utility rates can be a lot higher then what mine here are. Keep in mind, I'm sure the rated watts on a unit isn't exact, but it'll give you an idea.