Actual EV Miles vs Estimated EV Range

My observations suggest that it depends. Obviously if you are on a decline the charge lasts longer then if you are on an incline. Incline and decline are not just hills either. Soft incline and decline that you don't notice unless you are watching gauges closely. And long distance incline or decline where there are up and down hills the entire way but oneway is mostly decline and one way is mostly incline. Donner pass, I-80 from Tahoe to Sacramento, is one extreme example.
I-80 from a bit east of Buffalo to just west of Albany is another much less noticeable but substantial decline that can be measured with mpg going both ways on a calm day. Wind resistance is also a factor. If you are driving with the wind on a windy day then you turn into the wind for a segment of the drive you will most likely notice the mpg drop significantly. There is a prevailing westerly wind between buffalo and albany, so an emphasis has to be on a flat calm the entire distance when reading the gauge. It's also possible to see mpg decline especially approaching albany on I-80 from the west as the incline starts again.

But the ev gauge is one thing I don't fully understand yet either. I hope in time I will have a better understanding of what variables are used to show the driver how much further there is to go in ev.

 

I think the EV gauge is an estimation of the surplus, expressed in distance, above that which the hybrid system needs to function optimally for maximum fuel economy. I believe the range is calculated based on recent driving history.

 

Ah yes one of my first complaints (suggestions as Toyota called them in a survey) about the car when I first picked it up. I want numbers not just graphs. If you can calculate an MPG off of fuel flow in an injector how hard can it be to calculate power flow from the traction battery in the HSI? And I didn't really care if they used MPGe or kWh.