Notes and comments Cars are buildings: Building-like energy use in automobiles Valerie M. Thomas a,b,⇑ , Alan K. Meier c , Siva G. Gunda d , Thomas P. Wenzel c a School of Industrial and Systems Engineering, Georgia Institute of Technology, 765 Ferst Drive, Atlanta, GA 30332-0205, USA b School of Public Policy, Georgia Institute of Technology, 685 Cherry Street, Atlanta, GA 30332-0345, USA c Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 90R2000 Berkeley, CA 94720, USA d Department of Mechanical Engineering, University of California, Davis, 2132 Bainer Hall, One Shields Avenue, Davis, CA 95616-5294, USA article info Keywords: Light-duty vehicles Air-conditioning costs Electricity use in vehicles abstract This paper examines vehicle energy use as if vehicles were buildings. Vehicle air condition- ers are much less efficient than residential air conditioners, and in the US consume about 0.9 quadrillion BTUs (quads) per year, comparable to the 2.3 by air conditioners in resi- dences. Vehicle heating, in contrast, is a model of efficiency, running as a combined- heat-and-power system using waste heat from the motor. Electricity use from appliances such as DVD players, laptops, and refrigerators remains modest, although stand-by power use is growing. Technology and policy approaches used for buildings can address similar types of energy use in cars. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction People in the US and other developed countries spend more than an hour a day in automobiles. The primary purpose of cars is to provide transportation, but the driver and other occupants also accomplish other tasks while in their vehicles. Many of these activities are familiar to building researchers: people in cars drink, eat, listen to audio entertainment, shave, communicate with friends on the telephone, and watch videos. All of these activities traditionally occurred inside buildings and have either shifted or expanded to mobile use. Furthermore, appliances that once resided solely in buildings are now becoming common in vehicles or being moved from one to the other. The car has a building envelope, with walls, windows, doors, and air infiltration. These elements have R-values, transpar- encies, and air leakage that if not controlled will create thermally uncomfortable conditions. Like a building, a car is heated, cooled, and ventilated. The modern vehicle offers its occupants illumination, a range of consumer electronics, and food-re- lated services. These are all familiar end-uses in buildings. There are also increasing electric loads from vehicle-related equipment including security systems and electronic engine controllers that may remain operational even when the vehicle is not in use. 2. Cost and energy to produce electricity in a vehicle The fuel needed to generate a kWh of electricity in a vehicle varies depending on the device being powered and how and when it is used. Fig. 1 shows power generation modes in vehicles and their corresponding efficiencies. The conversion of the chemical energy of the gasoline into mechanical energy at the crankshaft is about 25–30% efficient (US Department of En- ergy, 2008). The belt that transfers power from the shaft to all mechanical loads is about 95% efficient (Gates Corporation, 1361-9209/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.trd.2011.01.010 ⇑ Corresponding author at: School of Public Policy, Georgia Institute of Technology, 685 Cherry Street, Atlanta, GA 30332-0345, USA. E-mail address: valerie.thomas@isye.gatech.edu (V.M. Thomas). Transportation Research Part D 16 (2011) 341–345 Contents lists available at ScienceDirect Transportation Research Part D journal homepage: www.elsevier.com/locate/trd