2012 Prius Plug-In Window Sticker

Interesting Point-of-view. Though that only driving 4000mi a year.

 

Despite my personal preferences I am capable of being objective.

I was really impressed when I saw the sticker with how little gas was used in the blended range. Its a shame really, because Toyota clearly tried very hard to use as little as possible. If they had just embraced blending as a design concept earlier, they could probably use more gas to really extend the cd period over more miles, which could be more or less efficient for a particular driving scenario.

From my perspective, I would like a car that ultimately lets you set the usage pattern for your particular drive, i.e. I'm running 6 miles to pick the kids up from soccer, stay all electric; I'm running 60 miles to visit grandmom, blend in gas to allow my charge to deplete over 60 miles; I'm driving 1000 miles to Disney world, just stay in HV on the interstate and I'll turn on the EV when we need to exit for stops, etc...

 

If the owner does 2 charges per day and it'll be 8,000 miles a year. Throw in long weekend trips and it could be 12,000 miles a year.

 

Emphasis on the word "they", since those buyers are not representative of the typical mainstream consumer.
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My mom only has a 3-mile commute (each way).

Imagine the killer MPG she'd get!
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Not a proper comparison. Volt and Leaf did the whole test on electricity. You have no way of estimating their electricity use over the same parts as the Prius did.

Prius PHV achieved 95MPGe for 11 miles.
Volt Achieves 94MPGe for 35 miles.
Leaf Achieves 99MPGe for 75 miles.

The differences between Prius and Volt in CD range are minor, and the Leaf is 5% more efficient in CD range. For difference travel profiles any one of them can be the most efficient overall.


If you want to say the Prius PHV will use less electricity overall than a Volt,then that is fair. Then the regular Prius or any pure ICE will use even less. And its not clear many people care about minimizing electricity use.

 

I will be recharging on average 3 times a day during the week, and possibly the same on week-ends.

In my case, most of the gas used will be the "mandatory" runs that the PIP will do every so often to keep the ICE and gas in the tank in good condition. Some longer trips on week-ends will use HV also.

 

That's not really a fair comparison either because fuel production for gas is much more efficient than electricity. Prius PHV figure contains some gas.

The only valid comparison is well-to-wheel, total energy efficiency. With that, Prius PHV comes on top.

 

Well, 21-23 is your estimation, mine is 35%, time will tell.

My problem with percent increase: Ultimate UF is 100% (or very close to it), it is only 150% of Volt average but 286% of Prius average (taking it as 35% EV). Percents increase cannot be compared straight forward.

You meant miles not time right?

 

Yea, the cord literally plug a hole in the MPG killing short trips.

 

Unfortunately, time probably not tell us much as getting real-world data on %EV usage will not be easy.


I don't see your point.. Achieving the 100% UF factor is a smaller percentage of the Volt average since the Volt average utilization is much higher. If one is looking at errors in measurement, or natural variations in a population, the ideal way is to look at z-scores, but we don't know the standard deviations. That would fully capture additive and approximately capture basic multiplicative noise. The next best approach is normalizing just using %difference from the mean, which captures additive noise between difference sources.

What is your recommendation for comparing error in estimating utility factor?

 

MPGe numbers are well-to-wheel efficiency numbers.

 

No, it is from wall-to-wheel. Fuel production is upstream (well-to-wall).

 

Sorry, you are right.

That said, you still can not claim that "fuel production for gas is much more efficient than electricity" without referencing well-to-wheel numbers as efficiency varies greatly depending on where your oil and where your electricity comes from.

 

Right. So, using average figures, gasoline production efficiency is about 84% and electricity is about 39%.

 

I am sorry but I really don't understand what you are trying to tell us. I understand upstream emmissions when we are talking about the cars, but I don't really get upstream efficiency.

DO you mean in some empirical sense there is more energy left in coal ash than oil sludge? What does that have to do with the cars? If my PV panels are only 22% efficient does my car get penalized for wasting all that other sunshine?

Is there some total pool of BTU's out there you want to make sure get utilized as efficiently as possible? How does that thinking jive with using renewable resources?

 

Uh, your chart right there says that wells to wheels electricity is more "efficient" than gasoline in the Prius.

 

The vehicle efficiency is just a subset of the entire chain of efficiency from well to wheel. Gas is least efficient at the combustion stage which happens to take place in the car. Electricity generation is least efficient in the power plant which happens outside the car.

The scope of EPA MPGe is only in the car. Therefore, the electric miles (MPGe) avoided it's least efficient stage in the chain because it was out of scope for EPA MPGe label.

It is not fair for EV if we only look at fuel production because it would be at disadvantage (39% vs 84%). On the same token, it is not fair for gas cars (including no-plug hybrids) if you only look at vehicle efficiency (37% vs 85%). We'll have to look at the whole process, combination of both.

I am not sure about the efficiency for the electricity generated from solar and renewable sources.

 

Yes you are correct, according to that Toyota chart. However, the point of discussion is the EPA label between MPG and MPGe.

Prius is rated 50 MPG. Leaf is rated 99 MPGe. From there, you would assume Leaf is twice more efficient than Prius.

If you look at the well-to-wheel efficiency, you can see they are about the same.

Prius PHV's 95 MPGe figure does not take account of that when blending of ~3kWh electricity and 0.022 gallon of gas.