What is 'normal' phantom drain for a US household?
Older Fridges can draw upwards of 300 W  (while in defrost for example), and can average over 150W even if they are working correctly.  If you've got two of them, that could be your load and could explain the variance (if one were in defrost while measuring).  1KVA &quot;Phantom&quot; load for a 3500 sqft house doesn't seem totally unreasonable.  You've already found 500-700w of draw.  Everyone's circuit breaker idea (in comments above) is good to localize which circuit the phantom drain is attached to.