Is wind the new ethanol?

These are boom times for wind power. T. Boone Pickens, the wildcatter turned oil baron, is building the world’s biggest wind farm, in the dry scrub of the Texas Panhandle—a $10 billion bet on wind’s future. Twenty-eight states have set ambitious mandates for renewable energy, with wind power shouldering most of the load; many compel electric utilities to get at least 20 percent of their supply from wind and other renewable sources between 2015 and 2025.

Those requirements, along with a generous federal subsidy (20 percent of wind energy’s costs), have fostered a turbine-building frenzy. Overall capacity grew by 45 percent last year alone. Several wind-power companies have been snapped up in recent years in a string of multibillion-dollar deals. In May, Jim Cramer talked up wind stocks on Mad Money while assembling a model turbine in the studio.

And why not? Wind power seems to promise zero emissions and an endless supply of cheap power.

Still, it’s hard to ignore the parallels to the recent ethanol boom, which was also fueled by mandates and subsidies, and which is now viewed almost universally as a disaster. Wind power is unlikely to cause a global food crisis. But heedless investment in it may provoke blowback of a different sort.

Though wind advocates say that we can reliably and economically use wind for 20 percent of our power needs, the experience of Texas, which leads the nation in wind power—2.9 percent of its electricity comes from wind—highlights two big problems: transmission and variability.

Pickens’s windmills (like most of Texas’s) will be in the west, where the wind blows the most. The big cities are in the east. This problem plagues wind power nationally: people typically don’t live where the wind blows hardest, so you have to send power from, say, upstate to downstate New York, or from the Dakotas to the cities of the Midwest.

Texas expects to max out its east-west transmission lines by the end of the year. More wind power means new transmission lines, which will cost between $3 billion and $6.4 billion. Accommodating wind power on the scale foreseen nationally may require 12,000 to 19,000 miles of new high-power lines crisscrossing the country (by way of comparison, the interstate highway system runs 46,837 miles), plunging large parts of America into NIMBY hell.

Wind variability presents a more fundamental problem. Texas’s experience, at less than 3 percent wind power, is again instructive. In February, an unexpected cold front calmed the state’s wind farms. As power ran out and backup generation proved inadequate, grid operators were forced to call on large industrial and commercial users to power down.

Wind farms tend to produce the most energy when it’s not needed—at night and in the spring and fall, when demand is low. The hottest, highest-demand days of the year are the days when wind’s contribution is likely to be near zero. So wind, if it is to meet demand reliably, must be backed up, typically by (emissions-spewing) natural-gas plants that can ramp up and down quickly.

Powering plants up and down is inefficient, and when backup power is included, wind energy costs 10 to 30 percent more than fossil-fuel energy, even without factoring in the cost of new power lines. (Wind-energy costs have risen, not fallen, in recent years.) And once you include backup power, the cost of averting carbon-dioxide emissions by building a wind plant rises to $67 a ton, according to Cambridge Energy Research Associates. Less sexy emissions-reduction strategies, such as increasing efficiency at current electrical plants, cost between $10 and $30 a ton.

Wind is indisputably a promising source of renewable energy—today, in fact, it looks like the most promising and practical source. But many kinks remain to be worked out. It would be a tragedy if wind power were killed in the cradle by overeager requirements that bring hidden costs, unreliable operations, and higher energy prices, inviting a backlash.

The way to address our greenhouse-gas problems is not to champion wind or any other “silver bullet.” It’s to pass a national carbon tax or a cap-and-trade system, and let the market find the most efficient way to cut emissions and reduce our dependence on oil.