Right now, Amazon has this device on sale for $13 or 39% off.Please Log In to view this link! I bought this the other week at full price and have been racing around my home plugging in everything I can into it. What it essentially does it gives you some insight as to how much power your electrical device(s) use and based on the cost of electricity in your area, it will determine how much it would cost to run it 24/7 for say a month or a year. For example, just my internet cable modem + router cost roughly $1.70 a month to run. 50 inch LCD Sony TV costs about $7 a month. Surprisingly, my older bedroom 30 inch TV costs $9 a month. Overall, it can be a Handy little investment even if it's more-so just for a conscious cost of running things.