Question

What statistical metric is applied to plug-in hybrid electric vehicles to account for the probability of a driver using the electric motor versus the internal combustion engine?

Accepted Answer

The statistical metric used to account for the proportion of electric versus gasoline usage in a plug-in hybrid electric vehicle is the Utility Factor. The Utility Factor represents the weighted average percentage of total distance traveled by a vehicle using electricity from the battery rather than fuel from the internal combustion engine. This metric is derived from statistical travel surveys that track the daily driving patterns of the general population. Because a plug-in hybrid has a limited electric-only range, the Utility Factor assigns a probability that a specific trip will be covered entirely by electricity based on that trip&#x27;s distance. For example, if a vehicle has an electric range of thirty miles, the Utility Factor calculates how often a typical driver will complete a journey within that distance. As the trip length increases, the Utility Factor decreases because the likelihood of the internal combustion engine engaging grows. Regulatory bodies, such as the EPA in the United States, use the Utility Factor to calculate a single combined fuel economy rating for plug-in hybrids by blending the electric-only efficiency with the gasoline-only efficiency based on expected real-world driving habits.

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What statistical metric is applied to plug-in hybrid electric vehicles to account for the probability of a driver using the electric motor versus the internal combustion engine?