It is possible to estimate a home’s energy needs in kWh, but it isn’t very accurate. You would have to add up all the wattages of ‘normal’ appliances (you’ll see what I mean by ‘normal’ later on in the post.)
For the above reason, it’s often difficult to estimate average watts. The best way is to simply take last year’s energy usage from your utility bill, which will be a good estimation of what you use.