Information Bridge: DOE Scientific and Technical Information - Sponsored by OSTI
Here's an SAE technical paper that reads a bit like a Honda press release, but it's full of good technical information about the Insight.
Page 8 has a plot that gives engine friction torque at 1500RPM for a number of different engines. The Insight's appears to be about 10Nm at 1500RPM, i.e. 2.1HP. That's about half the value for their baseline 1.8L engine.
It means that engine friction is about half as large as road load at 45mph, which explains why the Insight's EV mode is so disappointing. It's also a reminder of how important it is to shut down your engine when it's not in use.