Curious customers can plug their electrical products into the Kill A Watt and find out how efficient (or wasteful) they really are. This residential-grade device assesses power quality by monitoring voltage, line frequency, and power factor with accuracy +/- 0.2%. The Large LCD display monitors the kilowatt-hour consumption of electronics to learn how much they cost to run. Electrical expenses may be calculated by the day, week, month or even year. One-year manufacturer’s warranty.