I use a Kill-A-Watt and I love the thing! I hooked it up to just about everything in the house... We are not actively miserly with electronics usage, and we stick around 400-450kWh/month. The goal is to setup our electronics, and our house to do the miserly stuff for us so we dont feel inconvenienced.
In the winter, we have the thermostat set to 60 degrees, but we use electric blankets and layers to keep us quite comfortable. My home media server is setup to go to sleep between 11pm and 9am, it only uses 35W at full tilt anyway. All of our appliances are energy saving. All of our lights are CFL or LED. During the summer we use a whole house fan during the cooler hours and seal up the house during the hot hours... so no AC usage here and things stay very comfortable unless its 95+ outside then we will use a little AC from time to time.
One thing the Kill-A-Watt found was that the 3 DirecTV receivers that we had where always using 45W even when not in use. That alone was accounting for 100kWh/month, so we got rid of them and just use OTA + Hulu + Netflix using Roku boxes that use 3W to 6W. Our 5kWh PV system produces about 650kWh average a month, so we should be sized just right after we get my Brammo Empulse this summer and my wife's Tesla Model X a few years from now.