I Kwh = 1000 watts for 1 hour.
I have inserted the method for calculating your own wattage from your meter using the formula shown. It's simple math, so don't get nervous. Follow the directions shown and you can figure out what you are using for the whole house, if you're interested. You will need your residential rates from your utility. Most have them posted on line. Ours here with La Plata electric is 11.3 cents/Kwh. So you multiply your watts product from the formula by .113. Pretty easy! The example here is 5400 watts. Remember to calculate the number of hours at that sustained rate too. It's a bit tricky to know how the usage is changing, based on what's being used, and for how long. That's the key to getting an accurate number.