I have had one of these for several years, and it has more than paid for itself by identifying devices and appliances that use more than their share of electricity.
For example, most electronic devices draw some power while turned off. Usually this is a watt or less, but I have found some older devices such as a VCR which drew about 10 watts. That's about 90 kilowatt hours per year, which was costing me about $0.15 per kilowatt hour, or about $13 per year. Unplugging that plus a few other inefficient transformer-operated devices paid for the meter within a year. To identify these, I only had to plug them into the Kill A Watt and note the wattage. Since there are 8,760 hours (8.76 kilo hours) in a year, the cost of running a device for one year is:
watts * 8.76 * electric rate
For devices like air conditioners or refrigerators, it's necessary to run them on the meter for at least a day, then determine the average wattage. From that you can estimate the yearly cost. For example, I found out that an old upright freezer in the basement used 3.54 kilowatt hours over a period of 26 hours and 29 minutes. That works out to nearly 1200 kilowatt hours (1.2 megawatt hours!) per year, so it was costing me about $180 per year. It turned out we could unplug the freezer and consolidate our frozen food into the refrigerator.
USA + Intl
OWC Canada
OWC Canada
