Every since reading about Viridian Electricity Meter contest in WIRED magazine in 2001, I’ve wanted one. Except that the designs were all imaginary. It seems there’s now an Newfoundland company that can sell me what I want: look at the PowerCost Monitor:

With a PowerCost Monitor you can tell at a glance how much electricity your home is consuming — moment-to-moment and in total. This is the advantage of real-time feedback on your electricity. Why wait for your electricity bill when you can see what you are spending on electricity as you spend it! Tests in Ontario and elsewhere have proven that householders who use real-time feedback can reduce electricity use by as much as five to 20 per cent.

Best of all, it seems that you don’t even need an electrician to install these units: they strap over top of both electromechanical and electronic meters.