Just wondering. Under the same driving conditions will you get worse mileage if the engine has to charge the batteries?

By the time I hit the expressway in the morning the batteries are about 1/2 way charged. It seems to me based on the mpg gauge I don't get my best mileage for a while and I'm guessing it's because some of the ICE's power is being used to charge the batteries. I know it's not terrain related as everything is pretty flat around here.

Does anyone else find this? Does it make sense (does to me)? Or am I just staring at the gauge too much when I should be looking at the road?

I have the non-NAV version so I don't have the nifty display that shows mpg on a minute by minute basis.

There are times when I'm driving slow and "under load" or accelerating that the FE gage shows in the 20 to 30 range and the ICE is charging the battery. Letting off and reapplying the throttle won't kick in the battery mode and I just go back to the 20-30 range. It does not last all that long though (a couple of miles). When the battery is charged adequately I can let off and reapply the throttle and go to E mode. When I'm at speed (say 50 or 55) and there is excess horsepower, the ICE is sometimes still charging the battery, but it's with excess (normally wasted) horsepower and I get in the 50 to 60 mpg range.