Kill A Watt P4400 – P3 International Electricity Usage Monitor for $15.99 shipped after coupon code MLCK203005022525NL1. The coupon code is valid for the first 500 orders. Here is a screenshot for your reference. Kill-A-Watt identifies power-hungry devices by measuring their actual usage. Here is a review and a video clip about what this device can do to measure usage and help save energy.