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When I search "voltmeter" and "wattmeter" at Amazon I get about the same list of devices in the results. Most of them are multimeters with the ability to provide several different kinds of output. You saved yourself from confusing everyone by including the picture. BTW, the Kill-A-Watt you show provides several kinds of outputs (as is typical) and will calculate the kilowatt-hours for you without need for manually cranking through your formula.