Is the Prius green? I’m concluding the short answer is yes. This comes not from doing calculations myself, but rather relying on information from “major”-ish news sources.

I define green here as producing less CO2 over the entire life cycle of a car than the competition.

Most confusion on this issue stems from a 2007 report titled “Dust to Dust” by CNW Marketing Research (an automotive market research company) that concluded a Hummer is greener than Prius. Unfortunately I can’t easily find a copy of this report (CNW took it down) , but a variety of sources (here, here) document issues with the conclusions. Most notably, the report apparently listed the lifetime of a Prius as 109k miles and the Hummer at 379k miles. Consensus online appears to be the report is discredited. I think it’s telling that I can’t find any other mention of a credible report questioning the overall CO2 savings of a Prius (or other hybrid).

The Prius does indeed consume more energy during production than conventional cars, but driven to 160k miles, the Prius wins in terms of overall carbon emissions. ACEEE rankings, list Prius near the top of green cars.

A Fox News article also concludes Prius is green (have to scroll all way to bottom to find it).

There are a lot of reasons to buy a Prius. You get conspicuous conservation with your easy advertisement for how green you are. You get to drive in an obnoxious way while maximizing your mpg. Your car looks so weird it is bound to get attention (though not so weird now since it’s a best seller). And you can feel smug.

Driving a Prius won’t save the planet (whatever that means), but it appears to produce less CO2 over its entire life cycle than conventional cars.

My car broke down and repairs cost more than it’s worth. Time for a different one. I’ll likely get a Honda Civic or Toyota Prius. Do fuel savings from Prius justify price premium? No. It would take at least 8 years to reach breakeven between the two at current gas prices. I may buy a Prius anyway, but for other reasons.

Here’s the calculation (I ignore resale value, since I tend to drive cars to end of life).

I will buy used. I found these two options:
2012 Prius Two 51city/48highway $18,600 40k miles (Edmunds.com)
2012 Honda Civic: 29city/41highway $15,000 39k miles (Edmunds.com)

I probably drive 75% of time in city and 25% of time on highway. This gives following mpg:
Prius = 0.75*51 + 0.25*48 ~= 50.25 mpg
Civic = 0.75*29 + 0.25*41 ~= 32 mpg

I averaged ~10,000 miles/year in the broke-down car. Each car would consume following fuel:
Prius = (10,000 miles/year) / 50.25 mpg = 199 gallons
Civic = (10,000 miles/year) / 32 mpg = 313 gallons

In California, taxes and fees would add ~10% to list price, giving following out-the-door price:
Prius = $18,600 * 1.1 ~= $20,500
Civic = $15,000 * 1.1 = $16,500

The premium for a Prius is $20,500 – $16,500 = $4,000. A Prius consumes 313 – 199 = 114 gallons less gas per year.

With fuel price (F) and years driven (Y), we can calculate the breakeven point:
$4,000 = 114 gallons * F * Y
Y = $4,000/(114 * F)

If F = $4.20/gallon (current price), Y = 8.4 years.
If F=$7/gallon, Y = 5 years

I consider 5 years the acceptable payback period to buy the technology based on fuel savings alone. As you can see, gas prices would have to increase to $7/gallon to make that happen.

Considered another way, what is the likely premium paid to own a Prius over 5 years over a Civic:
Premium = $4,000 – 114 gallons * $4.20/gallon * 5 = $1,600

There are a lot of reasons to buy a Prius, but for me money saved on fuel is not one of them.