We sell and install a bunch of generators. The best way is to have the customer turn on every item they want to use (make sure the microwave is in use) and turn off everything else. Use an amp clamp to see the actual current on these circuits. Then increase this by 25% for inrush currents and items not drawing full normal loads. This is the minimum you want to use. It's been my experience that a 40KW-50KW unit will run most houses without disruption using 2 - 200 amp transfer switches. A 15KW model will run the basics using a sub panel and a 100 amp ATS. You can email me if you need more info or to purchase a Guardian Generator from us.
