Peak Oil and Hybrid Cars — supplemental material


Calculation Details for Plug-in Hybrid Vehicles

In 2003 there were 135,670,000 registered passenger cars in the USA. They were driven an average of 12,242 miles per vehicle, and consumed a total of 74,590 million gallons of gasoline. Their average fuel economy was 22.3 miles per gallon, or 9.5 km per liter (data source: US DoT Bureau of Statistics).

A typical plug-in hybrid-electric vehicle (PHEV) should be able to achieve in excess of 100 miles per gallon, but just to be conservative let us use a figure of 67 mpg (three times better than present-day cars).

At three times the gasoline-efficiency of regular cars, a fleet of substitute PHEVs should use 2/3 less gasoline, or 49,726 million gallons per year, whose production would consume 2550 million barrels of crude oil. (Conversion factor: each barrel of oil yields 19.5 gallons of gasoline.)

That is about 348 million tonnes of oil per year, or fully 38% of the annual oil consumption of the USA (which was 912.3 million tonnes in 2003, according to the BP Review of World Energy 2005). This reflects the fact that transportation soaks up an astonishing 70% of our petroleum consumption. Here we are only concerned with passenger cars, which consume 38% of our annual petroleum usage. The remaining 32% is consumed by all other modes of transportation: SUVs, trucks, airplanes, railways, and ships.

If we replace just 6% of our existing stock of gasoline-powered passenger cars with PHEVs every year, then our total oil consumption will decrease at a rate of 2.3% per year for ten years — just about enough per year to account for our share of anticipated reductions in world oil production due to Peak Oil during this ten-year period. It will be much more than enough, if consumers pursue other conservation measures as well.

Replacing 6% of existing stock means buying 8.1 million PHEV cars per year. Given that our current rate of new passenger car sales fluctuates between 8 and 9 million per year, that clearly implies that just about every new passenger car would have to be a PHEV. That cannot be achieved this year or next year, but if the pump price of gasoline continues to rise sharply then it is highly likely to occur by 2012, even without any change in existing government regulations and subsidies.

Let us suppose that the typical PHEV will have a 9 kilowatt-hour Lithium-ion battery capable of powering the car for its first 60 miles, with only occasional assistance from the gasoline engine, while consuming 7.2 kilowatt-hours of electricity. At $0.10 per kwh, that comes to just 72 cents, or 1.2 cents per mile. If the typical PHEV uses an average of 6 kwh per day of electricity from the grid — a conservative estimate — then that comes to about 2.2 megawatt-hours of grid-based electricity consumed per year, per PHEV (source: EVWorld).

Can our electric grid bear the burden of all the additional electricity demand as new PHEVs are put into service? On the assumption that 6% of our passenger car fleet are updated to PHEVs every year (8.1 million cars), that would mean an annual increase in electrical demand of 17.8 terawatt-hours. The annual rate of US electricity use is 4000 terawatt-hours, so we are talking about a 0.4% increase in electrical usage per year. The grid can handle it.

But suppose that we decide to entirely cover this increase with power capacity, whether from coal, nuclear, or solar sources. How many power plants will we need to build each year in order to generate an additional 17.8 terawatt-hours of electricity for our fancy new PHEVs? 17.8 terawatt-hours is about 2 gigawatt-years, and a typical large power plant has a generating capacity of 1.2 gigawatt-years.

I conclude that we would only need to build two large coal- or nuclear-fired power plants a year to fully support a mass conversion to pluggable hybrid-electric vehicles. If solar and wind generation increase, then we would need even less.

Last revised: 29 April 2006.


Dear Reader: If, in studying these calculations, you should find any error or omission, please send me a note. Thanks!

— Loren (cobb@Aetheling.com)

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