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Diesels and Hybrids: MPG and HP

Hybrid MPG and Horsepower

I’ve been curious to see what the next crop of hybrids -- the bigger ones, the versions of existing popular models -- might mean from a fuel efficiency point of view. There aren’t a large variety of hybrid models in the market for comparison (understatement), but enough information about some upcoming versions has come out to give me a little something to work with.


I took the data I could find about the combined mileage and horsepower of these different promised and delivered models, plotted it and came up with this chart on the right. Horsepower is the Y axis, combined MPG the X axis. (Click to enlarge.)

Running a linear regression on the plot produced a R2 value of 0.9092 -- in other words -- there is a pretty strong correlation between horsepower and mileage, even with a hybrid. (An R2 value of 1 represents perfect correlation.) As horsepower increases, the combined mileage decreases. (Certainly there are other factors to consider: vehicle weight, shape, transmissions, etc.)

Well, duh, you might say. So?

So. For all the undeniable good of hybrids (fuel efficiency increases of 30-50% are nothing to scorn), given the American tendency to want big and powerful vehicles, the net effect of hybrids from a gasoline consumption point of view is going to be reduced.

For example, the Toyota Highlander Hybrid SUV is projected to deliver 32 mpg -- much better than a gasoline SUV, but much less than the Prius’ 55 mpg.

Hybrids are a terrific tactical solution. They reduce gasoline consumption and they reduce emissions. They mitigate the strategic problem of fossil fuel dependence, but they don’t solve it. The more current buying and driving patterns stay the same (bigger and more powerful vehicles, more miles each year) the less mitigation hybrids can produce.

The danger we face -- especially in a presidential election year -- is a gross oversimplification and polarization of the debate around solutions for sustainable mobility.


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