The TED 5000 series of smart meters allow home energy monitoring in real time. You can even view your electricity usage from any Internet-connected device, including your mobile phone. This device is compatible with Google PowerMeter. Kits start at $199.95
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Just wanted to point out another similar device that I feel is a better product.
http://www.brultech.com/HomeEnergy/ecm1240intro2.html
The Brultech ECM-1240 monitors the main feed coming from the electric meter just like the TED units, but the brultech unit also allows you to monitor 5 subfeeds (breakers) in your breaker box. You can narrow down usage a bit better this way.
We have a similar product in the UK called Alertme.com
It uses a clamp and a energy meter on your main inlet box, and then you can use smartplugs on other devices to see how much each appliance draws. It also doubles up as a great Home Automation system (well kinda) switching on and off appliances when triggered by the system.
TED is one of the better units and does make an effort to be accurate in the power factor and voltage are used.
I just find the Brultech unit to be even more accurate, gives more channels, because one is not enough with fridges/freezers etc switching on/off to make confusing picture more baffling.
You can even use channel 7 to hook up and log your gas meter.
more here
http://albacontrols.wordpress.com/2010/01/20/ecm1240r1/