I went to the noping calculator (http://www.noping.net/english/) and ran the following cases:

Fixed parameters:

Hands on tops
Height = 70.5"
68 F
25 ft above sea level
no wind
no slope to the road
90 rpm cadence
20 mph speed

Next I ran several cases where the sum of the rider and bicycle weight was held constant at 220 lbs:

160 lb rider + 60 lb bike => 255 watts
180 lb rider + 40 lb bike => 265 watts
200 lb rider + 20 lb bike => 274 watts
220 lb rider + 0 lb bike => 282 watts

Something in their model says that it is much better to lose weight off the rider than off the bike.