This Instructable details a real-time web based household power usage monitor. The end result is a live chart in a web page that updates every 10 seconds with the instantaneous power usage for my entire house. The electrical current is measured on the main lines entering my home with AC clamps. The signal is then conditioned with a simple circuit and monitored by an ioBridge module
as it is measured and make kilowatt-hour calculations in real-time.