Hybrid Watchdog:  How will the EPA's new fuel economy estimates impact hybrids and the hybrid market?

The Environmental Protection Agency (EPA) is adopting new methods for deriving the gas mileage estimates posted on new vehicle window stickers.  The new approach is intended to provide consumers with fuel economy estimates that more accurately capture real-world driving conditions.  Although the new EPA fuel economy procedures will downgrade the gasoline mileage estimates for both hybrid vehicles and non-hybrid vehicles, nothing about the actual vehicles is changing, only the ratings.  However, the changes necessitate another look at the potential net savings of driving a hybrid versus a non-hybrid vehicle. The good news is that under the new estimates, hybrids save just as much fuel as under the old estimates.

The New EPA Fuel Economy Tests
In December 2006, the EPA announced new methods for calculating the city and highway fuel economy estimates provided on new vehicle window stickers.  This change is significant given that the fuel economy estimates provided on previous window stickers were up to 30 percent greater than what the consumer could ever hope to achieve.  The disparity is attributable to the current fuel economy tests which do not capture or fully account for modern driving conditions and vehicle technologies.  For more information, visit Fixing the EPA’s Fuel Economy Tests. 

Beginning with 2011 model year vehicles, the EPA will use new test methods to calculate city and highway fuel economy estimates.  The methods will include three additional tests designed to replicate three real-world conditions that can significantly affect fuel economy: air conditioning use, driving at high speeds or with rapid acceleration, and cold temperature driving.  The EPA’s final estimates will also attempt to take into account such driving conditions as road grade, wind, tire pressure, vehicle load, and fuel properties.  Significantly, the tests will use vehicle-specific testing instead of “across-the-board adjustments” to more accurately derive the estimates.

In order to provide consumers with more accurate fuel economy information before the full testing regime begins in 2011, the EPA will use a more sophisticated adjustment factor based on preliminary results from the new testing procedures.  The adjusted estimates will begin with model year 2008 and later vehicles.  For adjusted fuel economy estimates for earlier model vehicles, visit the EPA and Department of Energy's Fuel Economy website.

How will the new test affect hybrid electric vehicle fuel economy?
The impact of the new EPA tests on fuel economy estimates will vary from vehicle to vehicle. The EPA estimates that the city fuel economy estimates of most vehicles will drop on average by about 12 percent and by as much as 30 percent.  The highway fuel economy estimates will drop on average by about 8 percent and by as much as 25 percent.

The nature of hybrid technology (e.g., a smaller engine, second battery for onboard power, and the use of advanced hybrid control systems) makes some models more sensitive to driving factors like air conditioning use and cold weather.  As a result, the city fuel economy estimates for hybrid electric vehicles may be reduced by 20 to 30 percent and highway estimates may be reduced 10 to 20 percent.  Table 1 shows the highway and city fuel economy change for 2007 hybrid vehicles under the new approach EPA is using in 2008.

Table 1.  Change in city and highway fuel economy estimates for 2007 model year hybrid electric vehicles under the new approach EPA is using in 2008.

Despite the sensitivity of certain hybrid vehicles to driving conditions which downgrade the fuel economy estimates, the same hybrid models remain fuel economy leaders, save consumers money and represent the best environmental choice for most consumers.  In fact, in most cases, the EPA may have been underestimating the fuel savings potential of hybrids.  

Table 2 examines the fuel economy and gasoline savings differences between several hybrids and their conventional model counterparts.   It shows that choosing a hybrid over the conventional model makes sense despite any downgrading of fuel economy estimates because in many cases, the hybrid model achieves better fuel economy than its conventional model counterpart.¹  For example, the combined fuel economy of the 2007 Honda Civic hybrid drops from 50 mpg to 42 mpg under the new EPA fuel economy tests.  The combined fuel economy of the 2007 non-hybrid Honda Civic drops from 33 mpg to 29 mpg, which is still 11 mpg less than the hybrid version.  UCS analysis of the EPA estimates indicates that the fuel economy downgrade actually increases projected gasoline savings.  The new EPA method projects that the 2007 Honda Civic hybrid provides a slightly higher gasoline savings per 100 miles over the conventional model compared to the non-adjusted fuel economy.  

Table 2. Change in Gasoline Savings for 2007 Model Year Hybrid vs. Conventional Models under the new EPA method.¹

Although the change in hybrid-vs.-non-hybrid gasoline savings may be different once EPA fully implements the new testing procedure in 2011, it seems that, in general, hybrid owners should keep bragging about all the fuel they are saving.  That said, if consumers are not made aware that hybrids under the new system are just as good as under the old, there is some risk of MPG sticker shock. It will be essential for automakers, dealers, and anyone writing about hybrids and the new tests to make clear that both hybrid and non-hybrid vehicle models will be affected by the new fuel economy tests.  Additionally, individual driving habits, traffic conditions, and other factors will continue to affect fuel mileage (so slow down, keep your tires pumped up and get that tune up you have been putting off).  Yet, thanks the new fuel economy test changes, consumers will be armed with more accurate information about the gas mileage and fuel savings they can expect when comparing new hybrid and non-hybrid vehicles.

1. The hybrid models were compared to the following conventional models: Ford Escape FWD 4 cylinder, 2.3 liter engine, 4 speed automatic transmission Honda Civic 4 cylinder, 1.8 liter engine, 5 speed automatic transmission Mercury Mariner 4WD 4 cylinder, 2.3 liter engine, 4 speed automatic transmission Toyota Camry 4 cylinder, 2.4 liter engine, 5 speed automatic transmission Toyota Matrix 4 cylinder, 1.8 liter engine, 4 speed automatic transmission