I don't usually post weird deals and things, but I just got an e-mail flyer that included getting Kill-a-Watts for under $20.
Killawatt purchasing link
That comes with free ground shipping and an "instant savings".
Add coupon code: EL20P on checkout to get your total down to $17.99.
Poof! Start saving energy for under $20!
I think I paid $35 when I bought mine.
The only down-side is that it comes in bulk packaging, but you didn't want that wasteful retail packaging anyways did you?
Kill A Watt P4400 - P3 International Electricity Usage Monitor - Bulk Package with Free Shipping
Monitor Your Electricity Usage, Kill A Watt, only $17.99
FREE SHIPPING
Coupon code: EL20P
Item# EL-006-0428