Lighting ... or Correct Me if I am Wrong

I have been looking at the compact fluorescent lighting available
(e.g.,from all-glass: www.all-glass.com) to replace my current
standard fluorescent setup.

Now correct me if I am wrong, but it looks to me that if you have a
48" tank, for example, and you have two 55 Watt compact fluorescent
bulbs -- one on each side of the divider -- then the combined wattage
(110 wattage) is not really what the plants are getting. Instead, it
seems, that each side of the tank will receive approximately 55 watts
+ some small additional wattage indirectly from the other side of the
tank.

This seems to be less than my current setup where I have two 48" 40
watt bulbs. Here both lights are on each side of the tank and, given
an even distribution of 40 watts eminating from the bulbs, each side
would receive a total of 80 watts; arguably higher than the compact
light alternative.

Is this scenario incorrect in some way or does it make sense ?