The difference between LEAF and Volt from the EPA fuel efficiency label

In November, the U.S. Environmental Protection Agency (EPA) announced fuel efficiency labels for the following two vehicles. The two vehicles are the Nissan LEAF (Chinese name: 葉风) scheduled to be launched in Japan and the United States in December 2010, and the General Motors Chevrolet Volt (Chevrolet Volt) scheduled to be launched in the United States in December. This label is mandatory for new vehicles to be marked on the vehicle when they are sold, in order to facilitate consumers to compare the performance of the vehicles. With the launch of electric vehicles (EV) and plug-in hybrid vehicles, this label has also adopted a new style that is different from the previous gasoline vehicle labels.

The label mainly indicates four points: fuel efficiency, fuel (electricity) cost, driving range, and environmental performance. As an EV, the LEAF is driven by only electricity, so the content on the label is relatively simple. First, in terms of fuel efficiency, the EPA uses the MPG equivalent (equivalent to miles per gallon), which is a value obtained by converting the average electricity consumption per mile into gasoline. The LEAF is 99MPG equivalent (equivalent to 42km/L). Originally, LEAF does not use gasoline because it is an EV. However, in order to compare with other gasoline vehicles, the amount of electric energy is converted into gasoline and then indicated. The calculation formula stipulates that 1 gallon of gasoline has the same energy as 33.7 kWh of electricity.

The Volt's value is divided into two cases: when it is running only on electricity and when it is running only on gasoline. When it is running only on electricity, it is 93 MPG equivalent (39.5 km/L equivalent), and when the electricity is exhausted and it is running only on gasoline, it is 37 MPG (15.7 km/L). Toyota's "Prius" in the United States has 50 MPG (21.3 km/L) in hybrid mode, and the "Camry Hybrid" has 31 MPG (13.2 km/L) in the city and 35 (14.9 km/L) when driving on the highway. Therefore, when running only on gasoline, the fuel efficiency of the Volt is slightly higher than that of the Camry. Assuming that the practical driving mode is a mixture of EV mode and gasoline mode, the EPA estimates that the fuel efficiency of the Volt is 60 MPG equivalent (25.5km/L equivalent) when the two modes are combined. In this way, the fuel efficiency of the Volt is higher than that of the Prius.

In terms of fuel cost, the LEAF costs $561 (47,000 yen at 84 yen to $1) for 15,000 miles per year. This is the value assuming that the price of 1 kWh of electricity is 11 cents (9.2 yen). For the Volt, the cost of driving only in EV mode is $601 (50,000 yen) and that of driving only with gasoline is $1,302 (109,000 yen). The cost of driving only in EV mode is not much different from that of the LEAF. The price difference is caused by the LEAF's slight improvement in fuel efficiency (MPG equivalent).

When it comes to driving range, this may be the biggest concern. This is because the EPA label shows the LEAF's range of 73 miles (117 km), which is much shorter than the manufacturer's advertised range. Nissan says that the LEAF can travel 160 km in LA4 mode without air conditioning, and 200 km in Japan's JC08 mode. In the EPA's test, the EPA repeated the test five times under constantly changing driving conditions and air conditioning conditions, and the range on the label was calculated. The result is very different from the data Nissan has disclosed. Which statement is actually correct? Although the authenticity still needs to be identified, if we look at the conclusion, the range of EVs will vary greatly depending on driving conditions, so it can be said that both data are correct.

On Nissan's US website, the range of LEAF under various conditions is marked. The company says that the range will vary between 62 and 138 miles (100 to 222 km). According to reports, in the test mode called LA4, if the maximum speed is 56.7 miles (91 km/h), the average speed is 19.59 miles (31.5 km/h), the air temperature is 68 to 86 degrees Fahrenheit (20 to 30 degrees Celsius), and the air conditioner is not turned on, the cruising range can be 100 miles (160 km). In addition, when driving at a constant speed of 38 miles (61 km/h), the cruising range can be increased to 138 miles (222 km). On the other hand, when the average speed is 49 miles (79 km/h), the air conditioner is turned on, and the air temperature is 110 degrees Fahrenheit (43 degrees Celsius), it will drop to 68 miles (109 km). The shortest cruising range is when the air conditioner is heated at a low temperature of 14 degrees Fahrenheit (-10 degrees Celsius). If driving at a low speed of 15 miles (24 km/h), the cruising range will drop to 62 miles (100 km).

It can be seen from this that the EPA's 73 miles (117 km) is a very strict value. The Volt was probably tested under the same conditions, so the 25-50 miles (40-80 km) range data released by GM is still convincing.

Figure 1: Nissan LEAF fuel efficiency label

Figure 2: Fuel efficiency label of General Motors' Chevrolet Volt