I've decided to entertain myself by crunching some numbers on Eco-cruise and whether it is really beneficial for an EV. And I'm pretty sure that the answer is that Eco-cruise actually provides almost no benefit for an electric vehicle.
In an ICE car the vehicle can't deal with "negative" power. That is, when cruising downhill it must use engine braking to "burn off" the extra energy to keep the constant velocity. Eco-cruise allows the vehicle some flexibility for accelerating which means that energy is being converted into kinetic energy and not heat.
In the FFE the motor can regen power to maintain constant speed.
I worked out a spreadsheet to calculate the energy used to climb a hill and then descend the other side. This included Rolling Resistance and Air Drag.
It had variables for grade and distance(uphill and downhill). It also assumes that the vehicle returns to the initial velocity (at the beginning of the uphill) when it reaches the bottom of the downhill.
Just for the point of comparison I set the ICE energy usage to 0 when the energy would go negative. Really though because the ICE is still running this would be a positive number (and therefore the difference would be even greater).
The main point is at the very bottom... the EV has no net savings with Eco-Cruise, whereas the ICE does. There may be some other minimal forces at play that could make it more friendly but I think this shows why they didn't bother with Eco-cruise. The annoyance to other drivers wouldn't improve the efficiency.
**** EDIT ****
I realized that I was not properly calculating drag for the eco-cruise case. Since drag is proportional to velocity^2 it certainly does affect the outcome. As a result there is a small net gain for the FFE, but much smaller than for the ICE.
Numbers updated below
**** /EDIT ****
That's not to say that driving style doesn't matter. On local roads (where you aren't using cruise control anyway) you would certainly benefit by careful driving up and down hills. This analysis is obviously a relatively perfect scenario.
I will happily share the spreadsheet with anyone who asks. Feel free to check my numbers, I could have made a mistake.
Code:
Constant Speed (Standard Cruise)
FFE ICE
Energy (total) 276.7584949 320.5135982 Wh
Uphill 320.5135982 320.5135982 Wh
Downhill -43.75510332 0 Wh
Eco Cruise
Energy 267.4741485 286.2745674 Wh
Uphill 286.2745674 286.2745674 Wh
Downhill -18.80041884 0 Wh
Net Energy: 9.284346363 34.23903084 Wh