Wayne Brown's simulator predicts the following for the NHW20:
- 15F: 41.3 MPG (w/o heat)
- 15F: 39.0 MPG (with heat set to 68F)
- 32F: 43.7 MPG (w/o heat)
- 32F: 42.0 MPG (with heat set to 68F)
- 68F: 49.7 MPG
- 85F: 53.1 MPG (w/o AC)
- 85F: 51.8 MPG (with AC set to 78F)
These assume level terrain, smooth dry pavement, no wind, steady speed, Michelin Hydroedges inflated to 50/48, and 300# for occupant and cargo.
I assume your numbers are for the NHW11, which I would think ought to be a tad lower. Are you assuming the same terrain, pavement, wind, and steady-state conditions?
Regardless, when I report expected fuel economy, I generally include statements about these assumptions so that one who reads them may be less likely to think they can expect comparable results in, say, a 10 miles per hour head wind or a downpour.
I recently plugged simulator numbers into a spreadsheet for several temperature ranges (and other variables) for purposes of making charts as needed. An example can be found via this PriusChat
post. I'll be glad to generate a chart for you to include, if you think it helpful.