And actually, contrary to what might seem common sense, this engine warm up period where the ICE runs regardless can actually yield really good FE. The HSD will try to let the engine idle to warm up and drive the car mostly from battery. I used to hate the fact that the ICE always ran for a minute or two, now I see it as an opportunity for a minute or two of high FE if I'm nice to the pedal.

Two climate control systems, one inside and the other at the tailpipe.

2007 Camry Hybrid (in service June 2006)
FE: 6.67L/100km or 35.3 mpg (6.11L/100km or 38.5 mpg in summer)