Actual PiP eGallon - Is this correct or even useful?

Math OCD: If you are assuming a 12% charging loss then you want to divide by 0.88 rather than multiply by 1.12

Mike

 

Another approach would be to use the kWh of energy in a gallon of regular gas. There seems to be some variance, but 33.7 kWh/gallon seems to be a good number. This really points out how inefficient the gas engine is when one computes the EV MPGe. On my first tank, using the EV ratio data, I got about 160 MPGe!

 

if i get 15 miles per charge at a cost of .50, and 60mpg in hybrid mode, does that make my egallon $2.00?

 

The calculation looks right.

Regular gas around here is $3.80 so you do save some money using electricity.

You'll have to keep in mind that, if you have to do many short trips, gas engine won't give you 58.79 MPG that you are getting.

There is synergy going on with PiP. EV miles are cutting out the MPG killing short trips. Gas engine is weeding out electricity sucking high speed driving. The way each fuel are designed to use is boosting each other's efficiency.

To put it another way, if you have a pure EV, you won't be able to achieve 236 Wh/mi since it'll have to cover highway driving as well as uphills. If you have a regular Prius, you'll likely get around 50 MPG because you'll have to do short trips that require engine warm ups.

I think it is good that you can go 59 miles with PiP for $2.95 with electricity and $3.80 with gas. Note that, you can't go all 59 miles with only electricity or only with gas. It has to be a blend of both in order to achieve that low cost.

So, what's your EV ratio?

 

agreed.^

 

i disagree. if i don't plug in and get 60mpg, it's fair to compare that to pure electric driving.

 

If gas is $3.50/gallon then 15 miles for $0.50 is 7 times 15 equals 105 mpg of equivalent cost.This is close to the EPA rating of 95mpg based on 33.7 kWh equivalent in energy to 1 gallon of gas.

Of course if you can get your charge for $0.15 (California PG&E rate E9 at night) its even better cost wise.

 

Those are all very good points.

On the other hand, he certainly "could" achieve 268 Wh per mile driving entirely in EV (236 doesn't including the assumed charging overhead). I averaged about 250 Wh per mile driving 1029 miles under a variety of typical conditions last month primarily on the highway in my 2011 Volt in EV mode. The PiP is at least as efficient in EV and maybe a little better. Some other all-battery cars appear to have comparable or better efficiency.

 

That's around 210 Wh per mile. I'm guessing you aren't including charging overhead which is how EPA reports MPGe estimates. With charging overhead it would be roughly about 140 MPGe which is very good.

 

If you get 60 MPG for all types of driving that you do, it would be fair to compare. The same goes for electricity -- if you get 15 miles per charge for all type of driving.

 

That's pretty good. May I ask at what speed?

 

I typically set the cruise control at 56 mph but occasionally drive up to 65 for short stretches. City driving is at the posted speed limit. Most of my electric miles are on flat highway but a few days a month when I'm running later than usual and want to avoid bad traffic I take highway 280 which has many substantial rolling hills for 40+ miles. I live in San Francisco now so some city driving includes substantial hills.

I just checked my 12 consecutive month statistics:

Total miles: 24,440
Electric miles: 17,088
Gasoline miles: 7,352
Total MPG: 153
Total gasoline: 160.21 gallons (US)
Total electricity: 3,783 kWh (no charging overhead)

EV efficiency works out to 221 Wh per mile or 250-260 Wh per mile (assuming 12-15% charging overhead).

HV efficiency works out to 45.9 mpg. The average 2nd gen Prius on fuelly.com gets around 45.5 mpg and the average 3rd gen Prius Liftback gets around 48 mpg.

I've checked the gasoline consumption on the Volt display vs. the pump for the last 6-7 tanks of gasoline and the Volt display has never been more than 1.2% optimistic and is roughly about 0.5% optimistic on average although I haven't tallied up the exact average yet.

Update: I tallied up my last 6 tanks of gas. The pumps said I used 40.667 gallons. The Volt display says I used 40.42 so the Volt display is about 0.6% optimistic over those 6 tanks.

So, I'm doing about as well on HV as the average fuelly.com 2nd gen Prius driver.

 

56 mph is a smart choice because beyond that, the wind resistance gets so high that Wh/mi would be much higher. I think it is the reason PiP was designed to start the gas engine above 62 mph.

You could do 100 mph in EV with Volt but that would be foolish/wasteful, considering the cost and recharge time of the battery.

If I recall from your one week test with PiP, you got 65 MPG on regular gas.

 

Yes, I was using the kWh reported on the EV ration display.