Kill-A-Watt Electricity Usage Monitor for $17.99 shipped after code EL20P. Here is a screenshot for your reference. Note that it comes in OEM packaging, which means no pretty retail box and marketing materials but is otherwise identical. Kill-A-Watt is a tool that will help identify power-hungry devices by measuring their actual usage. It’s simple to use and can easily pay for itself quickly. We have a couple of them and have found them to be, uh, fun, amusing, and most importantly, very useful. Here is a review and a video clip about it.
Originally posted earlier, this deal has been revised.