Connect your appliances into the Kill A Watt, and assess how efficient they are. A large LCD display counts consumption by the Kilowatt-hour just like utility companies. You can figure out your electrical expenses by the hour, day, week, month, even an entire year. Monitor the quality of your power by displaying Voltage, Line Frequency, and Power Factor
Customer Rating: 
Summary: Handy little gadget
Comment: This tool will answer power consumption questions eg Should I leave the computer on when I'm not using it? Or, How much electricity does my TV use when it's on or when it's off? (They need to make one for 220 volt use also. This is limited to 15 amps at 115 volt appliances.)
Customer Rating: Summary: Works but awkward
Comment: The meter works as advertised and gives the the data I want, but it is unnecessarily awkward and difficult to use. Its not obvious from the photo that the other electrical connection is on the back and will block both sockets in an electrical outlet. The rear plug stands out from the back, so if you use an extension cord, the device won't lie flat nor stand up. The final annoyance is that the device has no memory if it is disconnected. The idea is to get the accumulated electricity use over a day or week, but if the device get disconnected from the wall socket or extension cord while wrestling with its awkwardness, all the counters reset to zero.
Next time need a product like this, I will look for a different device.
Customer Rating: Summary: Excellent little gadget
Comment: This thing works amazing if you are looking for power hungry gadgets in standby or are just curious how much power a device uses
+ Inexpensive
+ Measures pretty much anything you could imagine, including Power Factor, which in helpful in adjusting the PF for your entire house
+ Actual kWh measurement is really helpful to easily calculate the monthly or yearly cost of a gadget
+ Very simple to use
- Screen definitely needs a backlight of some sort, trust me you will need a flashlight
- A battery backup would be nice, but not necessary, to store some information
Customer Rating: Summary: Surprising how revealing this unit is......
Comment: I didn't know that this was still available. It may encourage saving electricity. I plugged my son's PS3 into it. Just push the on button and watch the wattage jump.
Customer Rating: Summary: catraveler
Comment: I purchased the Kill-a Watt P4400 a few years ago, and have used it numerous times to verify the power consumed by tv's,refrigerators, stereo equip., small A/C (less than 15amp). The only problem was a miss alignment of one of the reciptical pins, it was off center and the unit under test connector pin went down on the side instead of BETWEEN the recipticle contacts resulting in overheating the connector pin and partially melting some plastic. A slight adjustment and all is well. A good little tester!
;){kind=small}
View large
