I don't think I see the point of riding a geared bike if you're just going to mimic your static singlespeed GI. Unless you really want to collect that one empirical data point.
On average.
I ride a lot of flat and my engine only does X over distance Y. Matching what my usual sustained cadence and speed is not wrong.
I can keep 35kph up no problem on a non-windy day. Why would I park in a gear with the same cadence but that nets me 29kph? I won't be working as hard.
I'm no roadie (close), but I have two modes of riding. Exercise and "going for a rip". The exercise part of my riding I like to maximise.
So with a geared bike I would like to keep my efficiency as close to what I have on my fixed, but when I hit an incline I just change gears to make it easy. Maybe I just view my road bike as the "easy ride". I'm not really getting my point across I think. :|