SupermediaStore.com offers the
Kill A Watt P4400 Electricity Usage Monitor
sold out) for $22.49. Coupon code "EL20P" cuts it to
. With free shipping, it's the lowest total price we could find by $6. It features a large LCD display that will calculate electricity consumption by the Killawatt-hour.
Update: Buy.com offers P3 International's Kill-a-Watt P4460 EZ Electricity Usage Monitor, model no. P4460, for $29.99 with free shipping. That's a $7 overnight drop and the lowest total price we've seen.
It improves upon the P4400 by giving you weekly, monthly, or yearly forecasts.