They actually VERY accurate. I've measured before with other diagnostic equipment.
As long as you are not using it to measure the Microwave power consumption...
Sorry to bring up an old thread, but I was having trouble with a kill-a-watt and measuring a microwave. The microwave supposedly has 1650 input and 1200 output watts. When I measured it with a kill-a-watt it showed input between 1900 and 2000 watts.
Is there a problem with kill-a-watts measuring microwaves? Maybe because of their higher wattage?
When I saw the above comment by adaseb, I thought he or maybe someone else might know something about this.
Thanks for any help that can be provided.