Frequently Asked Questions
1. How do you rate the vehicles? (Answer)
2. I'm considering purchasing an online subscription. What exactly
will I see once inside? (Answer)
3. Has your book been reviewed? (Answer)
4. Diesel-powered vehicles are highly efficient. Why don't I
see them in your "Greenest Vehicles" list? (Answer)
5. I can't find the vehicle I'm looking for on your website.
Do you have a rating for it? (Answer)
6. Do you have Green Scores for used cars? (Answer)
7. How can I get a hard copy of the book? (Answer)
8. Even though electric vehicles don't have tailpipe pollution,
don't they still cause pollution from powerplants? (Answer)
9. Speaking of EVs, I don't see any this year. What happened
to them and how do they score? (Answer)
10. Are there any federal or state incentives available for purchasing
a green vehicle? (Answer)
11. Who is the American Council for an Energy-Efficient Economy?
12. I have additional questions about green vehicles. Where should
I direct them? (Answer)
13. How can bookstores order ACEEE's Green Book®?
How do you rate the vehicles?
We analyze automakers' test results for fuel economy and emissions
as reported to the U.S. Environmental Protection Agency and the
California Air Resources Board, along with other specifications
reported by automakers. We estimate pollution from vehicle manufacturing,
from the production and distribution of fuel and from vehicle
tailpipes. We count air pollution, such as fine particles, nitrogen
oxides, hydrocarbons and other pollutants according to the health
problems caused by each pollutant. We then factor in greenhouse
gases (such as carbon dioxide) and combine the emissions estimates
into a Green Score that runs on a scale from 0 to 100. The top
vehicles this year score a 57, the average is 30 and the worst
gas-guzzlers score around 14. Further information can be found
on the GreenerCars.com Methodology
A complete discussion of the ratings is given in our technical
report, Rating the Environmental Impacts of Motor Vehicles:
ACEEE's Green Book® Methodology,
available from the ACEEE
I'm considering purchasing an online
subscription. What exactly will I see once inside?
An online subscription will give you access to our database
of every vehicle we have scored for the past seven years (model
years 2000-2007; about 10,500 records in total). Subscribers can
search the interactive database (updated with new model releases
throughout the year) and build custom lists for comparing vehicles.
The "Best of 2007" tables
offer a sample view of the layout.
Has your book been reviewed?
ACEEE's Green Book®
has been widely praised as a valuable resource on vehicles and
the environment. But don't take our word for it. See what
others are saying.
Diesel-powered vehicles are highly efficient.
Why don't I see them in your "Greenest Vehicles" list?
It is still an open question whether diesel engines can be made
clean enough at a competitive price to extensively exploit their
efficiency advantage in the U.S. market. Most of the diesels on
the market, such as Volkswagen's Jetta TDI (turbocharged direct-injection),
score "Inferior" in Green Book ratings even though they
are more fuel-efficient than their gasoline counterparts. The
Jetta 1.9-liter TDI diesel automatic rates 35 MPG in the city
and 42 MPG on the highway, for an overall average of 38 MPG. That's
about 35 percent better than the 28 MPG average for the Jetta
with a 2.0-liter gasoline engine. But the diesel version is certified
to a standard that allows it to emit, for every mile driven, more
than eight times the amount of nitrogen oxide (NOx) emitted by
the gasoline-powered Jetta, which now qualifies as a Tier 2 bin
5 vehicle in the majority of the country.
Automakers are working to clean up the diesel vehicle. For example,
Ford is developing a version of the Focus sedan that uses advanced
control technologies targeted to meet California's ULEV II standards.
It has equipped its laboratory test car with a special NOx clean-up
device in which a solution of urea in water is sprayed on the
catalyst to selectively reduce NOx from the exhaust stream. The
vehicle also has a catalytic, soot-trapping filter to remove fine
particles. Widespread use of such systems is still some years
away, particularly if a new chemical such as urea needs to be
widely distributed along with ultra-clean diesel fuel. Engineers
at Ford and other companies trying to slash diesel emissions are
making up for lost time, since today's gasoline engines benefit
from over three decades of experience with ever-tighter pollution
I can't find the vehicle I'm looking
for on your website. Do you have a rating for it?
Our free website includes the year's greenest
and meanest vehicles, as well as the
greenest vehicles in each size class, given in the Best
of 2007 tables. The full ratings for all vehicles are available
through ACEEE's Green Book®
Do you have Green Scores for used cars?
In addition to the model year 2007 listings, ACEEE's
Green Book® Online
also contains ratings for all model year 2000 through 2006 vehicles.
Ratings for model year 1998 and 1999 vehicles are available in
hard copy in the 1998 and 1999 editions of ACEEE's Green Book®,
respectively. These can be purchased through the ACEEE
publications office. Ratings for older vehicles (model year
1997 and earlier) are not yet available.
For earlier model years, fuel economy is an important determinant
of greenness. So look for high-efficiency models on the Federal
Fuel Economy Guide website.
How can I get a hard copy of the
ACEEE's Green Book®
was produced in hard copy through model year 2003. They can be
ordered from the ACEEE
Even though electric vehicles don't have
tailpipe pollution, don't they still cause pollution from powerplants?
Yes, and we account for powerplant pollution in our ratings.
We also account for the pollution caused by refining and delivering
gasoline to the pumps for gasoline cars. Electric vehicles score
well even when powerplant pollution is taken into account because
they are typically very efficient vehicles by design. More importantly,
powerplant exhaust is not emitted "in your face" as street-level
pollution that directly exposes many people, as it is for gasoline
and diesel vehicles.
Speaking of EVs, I don't see any this year.
What happened to them, and how do they score?
Astutue subscribers of ACEEE's Green Book®
Online may notice that no electric vehicles
have been analyzed for the past couple years. This is because
we only include vehicles that are both readily accessible to the
public and of which a non-trivial number are built. Neither progress
in battery technology nor consumer demand for EVs has materialized
the way that many had hoped a few years ago. In 1999, Honda discontinued
its EV Plus model. A year later, General Motors stopped building
the EV1. GM has since decided not to renew the cars' three-year
leases when they expire. Chrysler's Epic electric minivan, Ford's
Ranger EV, Nissan's Altra EV, and other models are available only
for demonstration or limited fleet use, without new production
runs scheduled. In 2003, Toyota pulled the plug on the RAV4 EV
sport utility as well.
Some consumers raise the question, "Even though EVs have
zero tailpipe emissions, they use electricity from power plants,
so don't they just cause pollution somewhere else?" Yes,
they do, but electric vehicles are less harmful to the environment
than comparable gasoline vehicles for two main reasons.
One is that a given amount of pollution from a power plant is
likely to be much less damaging to health than a similar amount
from a tailpipe. To make an analogy, imagine two sidewalk cafés,
one at each end of a city block. Someone is smoking a cigarette
at a table at one of them. If you sit at the café at the
far end of the block, you'll be less bothered by the smoke than
if you are at a table in the same sidewalk café as the
smoker. Similarly, pollutants from vehicle tailpipes-emitted at
ground level and directly in city streets-expose people to higher
concentrations of noxious fumes than do power plants, which are
generally in more remote locations and have stacks that allow
the pollution to disperse before it reaches populated areas.
The other reason is that real-world emissions from gasoline vehicles
are still higher than the levels set by the tailpipe standards.
This problem is not as bad as it once was, since EPA has started
requiring automakers to meet tougher tests of their cars' and
light trucks' emission controls before selling them. Battery electric
vehicles avoid the emissions control malfunction and degradation
problems that have plagued gasoline vehicles. By comparison, emissions
from electric power plants have been more reliably regulated within
their permitted levels.
Nevertheless, the relative environmental advantage of electrics
is being lessened by ongoing reductions in pollution from gasoline
vehicles. This progress is due to both better testing and automakers'
growing experience with more effective emissions control technology.
In performing research for ACEEE's Green
Book® Online, we
examined the data on real-world emissions control performance.
These data show that manufacturers are doing a better job of equipping
their cars with controls that keep pollution low under a variety
of driving conditions. The California Air Resources Board (CARB)
and U.S. Environmental Protection Agency (EPA) check up on how
well auto pollution controls are working in practice. Such oversight
pushes the car companies to fix flaws in their vehicles' emissions
control equipment. Tighter tailpipe standards begin taking effect
this year and, once fully phased-in, will offer significantly
greater environmental benefits. Some of the cleanest vehicles
of 2007those meeting SULEV II and PZEV standardsuse
emissions control technologies that will become commonplace over
the coming years. The stringent standards, along with ongoing
testing scrutiny by EPA and CARB, will further cut smog-causing
pollution and save consumers money through avoided repair costs.
In contrast to smog-causing pollution, the global warming pollution
from any type of vehicle depends mainly on its fuel efficiency.
Carbon dioxide and other greenhouse gases are equally damaging
no matter where they are emitted. An important advantage of electric
vehicles is their potential for very efficient drivetrains. Electric
vehicle battery capabilities remain inherently limited and costs
are likely to remain relatively high. In the long run, the electric
drivetrain of choice may be the fuel cell, which chemically converts
a fuel directly to electricity. For now, improvements in vehicle
structures and gasoline drivetrain efficiency (and when available,
the extra efficiency boost of hybrid drive) provide the best choices
for affordable and practical designs that cause less global warming
Are there any federal or state incentives
available for purchasing a green vehicle?
As of January 1, 2006, many consumers purchasing hybrid-electric
vehicles became eligible for a federal hybrid tax credit. ACEEE
has computed estimates for the
credit amounts, which vary by vehicle. The Federal government's
fueleconomy.gov Web site provides additional tax incentive information
about both hybrid-electric
vehicles (HEVs) and alternative
fuel vehicles (AFVs).
Who is the American Council for an
ACEEE is a Washington, D.C.-based independent, non-profit research
group dedicated to advancing energy efficiency as a means of protecting
the environment and strengthening the economy. Read more about
the organization at its website.
I have additional questions about
green vehicles. Where should I direct them?
Please email any inquiries to firstname.lastname@example.org.
How can bookstores order ACEEE's
Contact Chelsea Green Publishing
at (800) 639-4099.