is used to determine the combined rating and guzzler tax. The procedure has been updated to FTP-75, adding a "hot start" cycle which repeats the "cold start" cycle after a 10-minute pause. Because EPA figures had almost always indicated better efficiency than real-world fuel-efficiency, the EPA has modified the method starting with 2008. Updated estimates are available for vehicles back to the 1985 model year. EPA testing procedure: 2008 and beyond US EPA altered the testing procedure effective MY2008 which adds three new Supplemental Federal Test Procedure (SFTP) tests to include the influence of higher driving speed, harder acceleration, colder temperature and air conditioning use. SFTP US06 is a high speed/quick acceleration loop that lasts 10 minutes, covers , averages and reaches a top speed of . Four stops are included, and brisk acceleration maximizes at a rate of per second. The engine begins warm and air conditioning is not used. Ambient temperature varies between to . SFTO SC03 is the air conditioning test, which raises ambient temperatures to , and puts the vehicle's climate control system to use. Lasting 9.9 minutes, the loop averages and maximizes at a rate of . Five stops are included, idling occurs 19 percent of the time and acceleration of 5.1 mph per second is achieved. Engine temperatures begin warm. Lastly, a cold temperature cycle uses the same parameters as the current city loop, except that ambient temperature is set to . EPA tests for fuel economy do not include electrical load tests beyond climate control, which may account for some of the discrepancy between EPA and real world fuel-efficiency. A 200 W electrical load can produce a 0.4 km/L (0.94 mpg) reduction in efficiency on the FTP 75 cycle test. Beginning with model year 2017 the calculation method changed to improve the accuracy of the estimated fuel economy, with lower uncertainty for fuel efficient vehicles. Electric vehicles and hybrids Following the efficiency claims made for vehicles such as Chevrolet Volt and Nissan Leaf, the National Renewable Energy Laboratory recommended to use EPA's new vehicle fuel efficiency formula that gives different values depending on fuel used. In November 2010 the EPA introduced the first fuel economy ratings in the Monroney stickers for plug-in electric vehicles. For the fuel economy label of the Chevy Volt plug-in hybrid EPA rated the car separately for all-electric mode expressed in miles per gallon gasoline equivalent (MPG-e) and for