An in Depth Comparison of the Volt Versus Prius

By Ray Iannuzzelli

I suppose I’ve always been a bit of a car guy. At the age of 16, my brother and already had three cars and performed a nearly successful engine rebuild on our 1957 Chevy convertible. During my adult life as a parent, engineer, runner, amateur cook, and car aficionado, I’ve had several GTOs, BMWs, and other non-performance cars. My two most recent BMWs are shown below.

2008 BMW 135i 2000 BMW Z3

However, my 2012 Volt is unique among all of them. Although not as peppy as the 135i that I traded in on my Volt, it is nearly as much fun to drive.

My recent fascination with electrics started a few years ago when I started a consulting gig for a battery supplier. Although not responsible for the design of vehicles, my job brought me close enough to get bitten by the electric car bug. I knew I had to have one. At this point I must give some credit to my dear wife of nearly 40 years. As an environmentalist of long-standing she convinced me back in 2004 that the new model Prius would be a wise investment. So, now on our second Prius (a 2010 model IV), we have some street credibility when it comes to environmentally friendly vehicles.

2012 Volt and 2010 Prius IV (background)

So How Do They Compare?

When you read that I was an engineer you just knew there would be some tech talk. I promise it will be short and sweet. I have compared my Volt and Prius. I wanted to know which car to drive on a trip. If we are planning a 100 mile journey which car is most economical? How about a 200 mile journey or longer?

The graphs below make the decision easy. Figure 1 is a comparison of the Volt vs. Prius mileage based on the energy used. It shows the breakeven trip at around 125 miles, i.e. for trips less than 125 miles the Volt is the clear winner.

Figure 1 Volt vs. Prius Mileage_energy

Figure 2 shows a similar graph to figure 1 except the mileage is based on the cost of the energy.

Figure 2 Volt vs. Prius Mileage_$

Figure 2 shows the breakeven mileage at around 85 miles, i.e. for trips greater than 85 miles the Prius is the winner.

The assumptions used to generate figures 1 & 2 are:

1) average EPA gasoline mileage
2) see figure 3 which is based on data from my volt between 11/18/11 and 12/25/11
3) average NH price between 11/18/11 and 12/25/11
4) based on recent PSNH electric bills
5) average Prius mileage between 11/18/11 and 12/25/11; below the yearly average of 50.1 mpg
6) data averaged from several Web sites

Figure 3 Volt Measured Electric Mileage

What I find interesting comparing figures 1 & 2 is the extreme volatility in the price of gasoline as compared to electricity. I would have expected a technical comparison to be much closer than is in fact the case.


Conclusions:

1. The criterion upon which a comparison can be made between the performance of the Volt and Prius is technically straightforward. If we use as a criterion the amount of energy consumed, the Volt shows a miles-driven breakeven of about 125 miles. Whereas, if we use the cost of the energy consumed, then the miles driven breakeven falls to about 85 miles. A clear implication here is that as gas prices rise relative to the electric rate, the $-breakeven will approach the energy-breakeven.

2. Of course the electric rate and gas price are both relative to the local market in which the comparison is made.

3. Also, the time-of-year and temperature are additional variables that will affect the comparisons.

Source: GM-Volt.com