Prius Plug-in Versus Volt: Which Costs Less to Drive?

USB if it helps at all I would adjust the volts kwh down from 12 to just a tad over 10 to maybe 10.5 (that is what I have observed to be usable), and I would also adjust the fuel mileage down to the low 30's.. I personally have seen 28-32mpg motoring about town. That is from my own personal observation, and hopefully it will give you some real world data instead of their best case scenario numbers. Granted the actual range is somewhat more than indicated, but it is about to go down into the 30's for the winter. That article also backs up my previous observation I made in another thread that it only takes about 70 miles to make the Prius a better option. I assume it will be less for the PiP seeing as my own 70 mile figure is based on our 2011 Prius which we regularly achieve 51-54mpg in and is not a PiP. I think the PiP cost will wind up being lower than what the graphs even show since we already know all the tips/tricks to getting good mileage around here, so will be interesting to see what the real world numbers for the PiP look like when people start getting them.


Taken after fully draining the battery from a full charge in 1 drive. Is why I doubt the 12.9kwh hour estimate. That would give me another approx 7-10 miles of range, and I would greatly appreciate that.

 

The point is to illustrate overall consumption, including the overhead of the charging process itself. So, you want more than just usable listed.
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True John.. I really need to get one of those meters to plug the charger into to see what the draw is for the charge and battery conditioning.. I keep forgetting about that. I pay a flat rate for the garage at the moment that has its own seperate electric so not really sure what the overall draw of the car is personally. Will certaintly be finding out next month though. Doing a little more digging USB's original figure is correct, so I apologize. I do sometimes forget the thing is a tad more complex than say plugging in a cell phone.

 

EV'rs can tell you that as a general rule, there's about 10% loss going from AC wall power, to DC battery charging, to storing the juice. Example from personal experience; although I'm calculating out 5.5 miles per kWh, I'm actually at 5.0 miles per kWh at the wall. Exactly 10% loss.

 

What are you using for miles per kiloWatt-hour?

 

A Fluke, and the Leaf's odometer. Pretty straight forward.

 

Why is the prius cheaper to run in CD at 87 mpge than the Volt at 94 mpge?

 

You are using the following assumptions to generate your chart:
15 / 3.6 kWh = 4.17 miles per kWh
35 / 12.9 kWh = 2.71 miles per kWh

Yet, at the Frankfurt auto show a few weeks ago Toyota itself gave a preliminary estimated battery range of 23 km or 14.3 miles on the European test cycle (NEDC). We have published NEDC results for the Opel Ampera (Chevy Volt with minor exterior cosmetic changes). It got 83 km or 51.6 miles of estimated battery range.

14.3 / 3.6 kWh = 3.97 miles per kWh
51.6 / 12.9 kWh = 4.0 miles per kWh

In other words, the Volt and PiP are identically efficient on the European test cycle. So, you can adjust things by taking the Volt's EPA computed miles per kWh from above (2.71) and use it for the PiP.

2.71 * 3.6 kWh = 9.75 miles

The chart should use 10 miles for the PiP, not 15.

That, together with a consistent EV range cost slope would push the crossover point to at least 60 miles or so. A skilled Volt driver going to a destination 60 miles away would use "Mountain Mode" as a crude battery "hold" button to preserve approximately 15 miles of battery driving near the eventual destination. I always drive this way on 50+ mile highway trips.

The result is that the gasoline is used during highway driving. So I would argue that a more realistic chart would use the EPA highway estimate of 40 mpg for the Volt.

This would move the crossover point even farther.

 

I think the other problem is not accounting for the oil consumption/cost during the "EV-esque" range of the PIP. It is blended operation so in addition to the kwh cost over the 15 miles he also needs to include the gas cost (I'd say about 35 cents [1/10 of a gallon or 150 mpg oil consumption in "EV-esque"]).

 

From that data, the Volt went at 240 watt-hr/mile. Which seems pretty good in my opinion. From what I've seen at low speed with the Hymotion kit on the Prius it is about 230 watt-hr/mile. So they both do come out pretty close when going on electric. I thought the Volt would do a fair bit worse than the Prius, but apparently not.

 

I am very skeptical of the volt managing to come anywhere close to the PIP in city CD fuel economy, given the weight differences.

As for the overall question, a smart PIP driver is going to embarrass the volt in cold weather driving

 

I'm jealous, my 2011 doesn't display the kwh used...

 

5 10 15 20 25 30 35 40 45 50 55 60
Prius 0.27 0.45 0.68 1.03 1.38 1.73 2.08 2.43 2.78 3.13 3.48 3.83
Volt 0.19 0.38 0.57 0.75 0.94 1.13 1.32 1.82 2.32 2.82 3.32 3.82

I get a cross over point somewhere just past 60 miles (wish I knew how to graph better)

 

The European Volt/Ampera also gets a "use gas" mode -- for mysterious reasons the U.S. version does not. All Volt's have a Mountain Mode that does act as a fixed function "use gas" mode by holding the last 15 miles of electric range.