Maryland requires that its electric utilities buy part of their electricity from renewable sources, a portion that will grow to 20 percent by 2022. Mike Tidwell's commentary in Wednesday's Sun argues that the General Assembly should carve out a portion of that requirement and reserve it for offshore wind power ("A propitious wind," Dec. 5). This carve-out would be at the expense of other renewable energy sources. It would do little for the environment and could increase consumer costs.

The General Assembly should resist such efforts to dictate how the renewable energy target is met. Is the best way onshore wind, offshore wind, solar, geothermal, burning of biomass and landfill gas, or some other technology? The assembly shouldn't decide; these sources should compete toe-to-toe in the market. The sources that provide the most value (in terms of power when and where consumers want it) at the least cost while meeting the renewable goal should be chosen.

There are good reasons to doubt that offshore wind is actually the best way to lower greenhouse gas emissions and keep electricity bills down. Offshore wind power plants are slightly more productive than onshore wind plants but not enough to make up for the much greater construction and transmission costs (as much as double onshore costs). In research we have done for Great Britain, for example, we concluded that offshore wind power is economically uncompetitive with onshore sources for precisely this reason. Furthermore, unpredictable wind power is less valuable to energy consumers than predictable biomass or landfill gas sources that will be there whether or not the wind blows.

Regarding jobs, what offshore wind advocates fail to point out is that costly renewable energy creates construction jobs precisely because a lot of money must be spent on construction. Paying more than necessary for renewable energy robs jobs from other sectors in the economy because energy consumers will have less money in their pockets to spend elsewhere.

If offshore wind cannot fairly compete with the many onshore renewable options we have, the assembly should not give it an advantage by putting a thumb on the scale. Earmarking part of the 20 percent for offshore wind power will depress what the market is willing to pay for other clean sources and risks stifling the innovation that we need in renewable technology. If we have learned anything from economic developments over the last few decades, it is that "game changers" or "disruptive technologies" come from unexpected places.

Here at Johns Hopkins, we are developing tomorrow's biofuel, wind, photovoltaic and fuel cell technologies. Which will be best for Maryland in the 2020s can't be predicted. What Maryland's energy policy should do is welcome renewable energy from unexpected places; the market, and not the General Assembly, should pick the winners. If offshore wind energy is as economically beneficial as Mr. Tidwell argues, the market will choose it to meet Maryland's renewable goals, and it will not need a special carve-out.

I share the goals of Mr. Tidwell's Chesapeake Climate Action Network of lower pollution and power costs. Allowing all technologies to compete fairly to achieve our environmental goals is a better way to do that than to make special deals that favor certain renewable technologies over other clean energy sources (including other renewables, energy conservation and, yes, nuclear). If the assembly wants more renewables than the present 20 percent target, let it raise the goal, but not predetermine the winner.

Benjamin F. Hobbs, Baltimore

The writer is Schad Professor of Environmental Management and director of the Environment, Energy, Sustainability & Health Institute at Johns Hopkins University.