I'm pretty sure Jeff specifically builds his machines for low energy use. He's written about that before. Keeping device batteries "topped off" doesn't use much energy, either.
More likely is that Jeff's house is poorly insulated relative to his neighbors. Or that the "average" presented is extremely skewed and not actually representative. (Is Jeff's house actually <1200 sq ft?) It might be interesting to see how many households get reports indicating that they are "above average".
That makes no sense. Obviously the efficiency of any appliance will play into how it impacts your energy bill. Having a server that your neighbor doesn't have won't automatically make your usage greater than theirs unless they happen to have identical usage in all other respects.
Jeff's recent server build (which I believe is going to a colo and not sitting in his house anyway), uses 31 watts at idle and 87 watts at full load. Assuming the middle is typical (and this is likely a serious overestimate), you're looking at 59 watts, or 10kWh/week. You could offset this with a more efficient furnace, or better insulation. You could also more than offset this by hanging 3 loads of clothes per week instead of putting them through an electric dryer (~5000 watt).
More likely is that Jeff's house is poorly insulated relative to his neighbors. Or that the "average" presented is extremely skewed and not actually representative. (Is Jeff's house actually <1200 sq ft?) It might be interesting to see how many households get reports indicating that they are "above average".