Editor:

"A little plug for every car, a giant cut for carbon emissions" (July-August Yodeler) claims that dozens of studies show that electric cars and plug-in hybrids cause lower greenhouse gas emissions, even with the current mix of fuels used to generate electricity. But those studies compare people driving the same distances and driving plug-in cars similar to (or smaller than) their current cars.

In reality, a shift to electric cars will change people's driving habits for the worse, because such cars are far cheaper to drive than gasoline powered cars. The electric power costs about one-quarter as much per mile as gasoline - partly because electricity prices are controlled and kept below the market price.

Plug-in hybrids will become generally available during the 2010s, and I expect that virtually everyone will shift to them to avoid high gas prices. As a result:

• The current decline in mileage driven will end, and vehicle miles travelled will resume its upward trend. People's mileage will spike when they buy the plug-in car, and then it will continue to grow steadily, as it has in the past.
• The current shift to smaller cars will be reversed. Everyone will able to afford the energy to run a plug-in Hummer.
• Gas tax revenues, used to fund both highway repairs and public transportation, will decline dramatically, and will virtually disappear in a decade or so.

It is possible to deal with these problems if we plan for them in advance:

• To forestall the plug-in Hummer, there should be strict energy-efficiency requirements for plug-in cars, as there are for other electric appliances. Because electricity sells for less than market price, we need these requirements to prevent people from wasting it.
• To replace lost gas-tax revenues and to control vehicle miles travelled, we could use toll-everywhere congestion pricing, with a fee high enough to support improved public transportation.

Like most technologies, plug-in cars will create both benefits and problems. We can minimize the problems if we plan for them in advance, but the current mindless adulation of electric cars is preventing environmentalists from anticipating the problems they will cause.

I predict that, before 2020, the Sierra Club will be publishing articles saying that plug-in cars are causing more traffic congestion and sprawl, shortages of funding for public transportation and road repair, and increased demand for electricity that makes it difficult to fight global warming by phasing out coal-fired power plants.

Charles Siegel

Response by Sherry Boschert, author of the article.

I have seen no data suggesting that a shift to driving on electricity will worsen driving habits. Will plug-in vehicles cause drivers to adopt habits that increase energy consumption? My experience has been the opposite - driving on electricity seems to make drivers more aware of the energy consumed, and to increase their desire for energy efficiency. I agree that as gasoline supplies dwindle, we'll need to devise a replacement for gas-tax revenues, and I applaud policies that promote use of mass transit and that decrease miles traveled by individual vehicles.

Dear Sir:

A large reduction in carbon-dioxide emissions from autos, through the use of central-station-generated electricity via storage batteries instead of individual internal-combustion engines, will indeed, result. As for the "giant cut" indicated by the article's title - that may be somewhat delayed. There first has to be the retirement of the existing inventory of the somewhat more than 230 million cars in the U.S. alone, a process that will take at least a decade. Also, the mining and processing of the materials for the half-ton plus of electric-storage batteries needed by each car will entail a fossil-fuel usage - the emissions from which, properly, are chargeable to the plug-in cars.

The efficacy of substituting stored electrical energy depends, of course, on the fact that fossil-fueled central-station efficiencies are in the neighborhood of 50% whereas auto engine efficiencies are about 30% max, but generally less than 25% in the range of stop and go operations that is our lot. So ultimately the automotive carbon-dioxide emissions can, at best, be halved.

The transition time can, of course, be diminished by government edict. But if legislative action is to be resorted to, some alternatives should be considered: rationing of petrol, imposition of strict speed limits, reduction of weight.

The speeds for best miles/gallon are in the neighborhood of 30 mph, while at present city driving is somewhat in excess of this, and freeway speeds of 60 are not unusual. At the higher speeds the power required increases as the cube of the speed, so if overall average speeds, by legislative action, become 30 mph rather than the present 45 mph (my guess) the power usage would be the cube of 2/3 or somewhere between 1/3 and 1/4, with corresponding reductions in carbon dioxide (without the time, cost needed for research, development, production, and advertising of the plug-in components).

By a similar argument, reduction in CO₂ emissions results from automobile weight reduction - a 10 or 15% reduction in the stop and go city driving - by taking out the rear seats and getting rid of the spare tire and all that junk in the trunk.

The plug-in car is inevitable. But there are simple, cheap, and faster routes to automotive CO₂ emission reduction during the transition period - if we're willing to endure a little frugality.

Sincerely,

Ellis Lapin

Response by Sherry Boschert, author of the article.

These strategies for reducing automotive emissions apply to plug-in cars as well as gasoline cars. Lower speed limits and lighter vehicles reduce energy use in any type of car, and should be considered part of our portfolio of strategies for reducing greenhouse-gas emissions.