Does the hybrid Toyota Prius lead to rebound effects? Analysis of size and number of cars previously owned by Swiss Prius buyers

Hybrid powertrains are considered being a promising technology to decrease fuel consumption of passenger cars. Sales numbers of hybrid cars are expected to rise considerably until 2010. However, the introduction of more efficient products is often accompanied by rebound effects, which counteract the positive effect of increased efficiency. We investigate two kinds of direct rebound effects that could possibly occur when buying hybrid cars: (i) people could tend to switch from small and/or already fuel-efficient cars to the new hybrid car, and (ii) the average vehicle ownership could increase, if the hybrid car is often purchased without disposing of an already owned vehicle. A survey was conducted with all 367 buyers of the Toyota Prius 2 in Switzerland in the first nine months after market entry. Return rate reached 82.6% without sending out reminders. The survey-based approach does not allow us to investigate whether hybrid drivers will in the future drive more (the classical example of the direct rebound effect). Detailed data on the car replaced by the Prius and on the other cars owned by the household were collected. Our analysis shows that average CO2 emissions dropped from 2 10 g/km for the previously owned vehicles to 104 g for the Prius. Empty vehicle weight (curb weight) increased by 9 kg only, which is below the market trend. A constant population-averaged vehicle ownership still allows for a certain amount of first-time car purchases and for increasing vehicle ownership for individual households, as these additional cars are compensated for by other households disposing of a vehicle. We present a new vehicle ownership model which assesses whether the vehicle transaction behavior of a sample of new car buyers corresponds, on average, to constant or increasing vehicle ownership. It is based on disaggregated data from the Swiss travel behavior micro census. Model results are consistent with market data and data from literature. Model results show that if ca. 20% of car purchases do not replace a vehicle (for a population with an age distribution identical to Prius buyers), this still allows for constant average household vehicle ownership. Only 13.7% of the surveyed Prius buyers did not replace an old car. Hence neither of the two rebound effects investigated could be found though the sample would have been large enough to do so: vehicle size did not increase, nor did average household vehicle ownership. (c) 2005 Elsevier B.V. All rights reserved.