How does the EPA get their mpge rating? Do they actually measure the electricity going into the battery and then note the range achieved? This would take into account the charging efficiency. I see that they find the kWh/mi figure then convert this figure into mpge using 33.7kWh as the energy content in a gallon of gas. But I've seen a lot of different testing methods especially in regards to how Nissan was testing the leaf and how the EPA was testing the leaf etc...
I would have to say, not very accurately, when I drove the Leaf, MPGe was 84.... in reality, if I got 70, I considered my self lucky! MPGe seems to be somewhat accurate in flat Kansas, with no hills or Hwy/Freeway speeds involved! Fake MPG!!
The MPGe is a useful yardstick to compare the cars. Nothing says that it will be the same as your usual drive nor mine. If we just drive our Prime around town, the mpg display maxes at 199.9, 'because it can't display infinity...miles divided by zero gas. That has no relationship to the driver with the long daily commute nor the long vacation drive. MPGe is just a yardstick.
Plug ins are tested on the same cycles as any other car. The electricity is measured at the outlet during charging, so the MPGe figure does account for the charging inefficiency. I am pretty sure the charging is at Level 1. Level 2 is a little bit more efficient. Being a Japanese company, Nissan could have been doing testing with the Japanese cycles; they yield better numbers.
Charging in the EPA test is with L2 OP: For range calc: Battery is charged to full; Car driven to empty alternating between the FTP and HWFET cycles; Energy at the meter measured to charge up the battery to full. The City and Highway MPGe values are similar in construction but only one cycle is driven for each type of test and the City is actually a weighted average of 3 FTP runs: one normal, one after a cold soak, and IIRC one using A/C
I've always wondered about this. It seems like if you never really use the gas engine in your car thats extremely in-accurate. Do the Prime cars have a mi/kWh gauge?
Where did you get this info? My understanding was that the raw city and highway values, which are used for CAFE, come from the respective test. The results from the three new tests(cold, A/C, and high speed) are used to adjust those raw values for the window sticker. Detailed Test Information
My average miles/kWh on my Prime was 5.3 during the spring, summer and fall. That equates to 179MPGe. The EPA rating is 133MPGe. The average has now dropped to 5.1 because of winter, but that's still 172MPGe.
