Kill A Watt

The Kill A Watt (a pun on kilowatt) is an electricity usage monitor manufactured by Prodigit Electronics and sold by P3 International.

The unit is manufactured by the Taiwanese company Prodigit, which also makes 230 VAC models of similar appearance and functionality for European Schuko, U.K. BS 1363 and Australian AS 3112 receptacles, and a model compatible with 100 VAC for the Japanese market (2022-04,[3] marketed there as the Watt Checker [ワットチェッカー] Plus by other companies).

[10] Although identical externally, there have been several different versions of the Kill A Watt and Prodigit equivalents, all essentially of the same design, but with different PCB layout, packaging, and components.

[11] One shortcoming of the Kill-a-Watt range of devices is that they do not have the ability to store, transmit or transfer the readings, thus limiting their usage for any ongoing monitoring purposes.

To counter this shortcoming, a couple of openly available modifications have been published on the Web, to enable these devices send data wirelessly to a receiver.

By piggybacking on the device's on-board LM2902N op-amp chip, the creator was able to get readings for voltage and current and transmit to a computer, which then sent this to Twitter via handle @tweetawatt.

[15] The modifications use a customized clone of the Arduino chip known as the Moteino, making this version much cheaper, and requires much less soldering than the original design.