EPA rating and MPGe - error?

[ToddR]

The EPA ratings for the RAV4 EV of 74 MPGe (hwy) and 78 MPGe (city) seem incorrect.

Per the EPA energy calculation 1 gallon of gas = 115,000 BTU = 33.7 KWh, which seems reasonable, and is consistent with a cost based approach (see below). The problem with the EPA calculation is they are claiming that the RAV4 gets only gets 2.2 m/kWh (hwy) (74/33.7) and 2.3 m/kWh (city) (78/33.7).

These numbers seem unreasonably low, and I am curious how they were obtained. Based on the results I see in the entune app my EV efficiency of 3.0 m/kWh is pathetic compared to the top drivers that have efficiency rating between 3.4-4.0 m/kWh.

3.0 m/kWh = 101 MPGe

How is the EPA coming up with such low numbers?

Cost based approach:
1 Gal gas = $3.75
1 kWh = $.12
3.75/.12 = 31.25 kWh

 

[Dsinned]

Probably because the EPA test cycle(s) include driving less efficiently with the HVAC ON and the drivetrain always in "D" (i.e. reduced regenerative braking effect).

Case in point, while my wife drives the RAV during the week, the average efficiency drops quite noticeably. But, when I drive usually only on weekends, efficiency increases again, but never recovers as much as it loses while she is driving, even though she drive it over less distance overall than I do.

I practice hypermiling techniques almost ALWAYS when I drive it, including shifting to "L" quite often to maximize regenerative braking, and I only turn ON some accessories rather sparingly. When she drives, just the opposite . . . but admittedly, most people drive more like her and less like me, so the EPA rating more accurately reflects the driving style of a majority of people.

 

[ToddR]

I drive like your wife, and the lowest efficiency I have every gotten is 2.8, and that was on a short (~1mi trip). As an experiment I will blast the AC and use "power mode" to see if I can get closer to the official EPA number.

 

[TeCKis300]

Dsinned, my wife and I have completely opposite roles to your situation. My wife hates it when she see's her Monday morning charged range estimate quite a bit lower than what she had nurtured it to the previous Friday.

Several factors at work helping me eek out my terrible weekend efficiency - which has seen as low as 2.2 m/kWh :
1) My lead foot
2) Driving with the whole family in tow
3) A/C on, and set at either eco lo or normal
4) Elevation gain driving home

I'm plenty capable of hyper-milling and I've seen 3.9 m/kWh. But I figure even if I'm lead footing it, it's still rather efficient to my ICE in the grand scheme of things.

 

[TonyWilliams]

EPA considers energy consumed "from the wall". Even if you get the 2.7 miles per kWh as measured from the dash that the EPA range rating (92 - 113 miles at 80% and 100% charge) is based on, the actual "from the wall" total energy consumed is much more.

Charger losses (big) and EVSE losses (tiny) are included. My last measured full charge was 50.x kWh from the wall for 41.8 kWh usable, or about 83%. Using that value times 2.7 equals 2.24.

How the 5 cycle test is performed is all on the EPA website.

 

[SeaMonster]

Cool, it's nice to have a formula. I've been wanting to better calculate comparative numbers. On Monday I drove 55 miles from Tiburon to Sunnyvale and averaged 4.1KWh/m for that trip. (Start and stop at basically the same elevation.) If I use the 83% efficiency, that means I was getting 115MPGe. Nice.