They also sell meters that will tell you how much juice an appliance is using. You could put it in a closet and see. Figure on opening the door x amount of times per day and that you will likely need more power in the winter. If you decide to test it, I'd love to see the results.
https://www.amazon.com/P3-P4400-Ele...F8&qid=1502646667&sr=8-3&keywords=usage+Meter
https://www.amazon.com/P3-P4400-Ele...F8&qid=1502646667&sr=8-3&keywords=usage+Meter