A while back, I was able to check out the accuracy of my meter by using the Watt-hour Dot Display
on the LCD
http://ecorenovator.org/forum/conser...-yourself.html
by plugging in a space heater (and nothing else), then measuring the line voltage,
and line current with a clamp-on amp meter.
(Watch those little bars in the lower right corner of the LCD, in this .GIF pic)..
The watts displayed on the meter, matched my volt meter x clamp-on amp meter almost exactly.
I used those little bars to calibrate the Whole-House power monitor that I was using to monitor my heating system (not the whole house).
Many new meters have those little flashing bars, but most folks have no idea what they mean..