The bulk of the discussion this afternoon at the Plug-In Vehicles 2008 conference focused on the enormous hurdles that stand in the way of plug-in vehicles significantly increasing their market share in the near future. These include developing better batteries (appropriately, Nissan and Toyota both claimed today to be making progress, and in this month's Atlantic Jonathan Rauch profiles GM's effort), and eventually providing incentives for consumers to trade in their gas-powered cars for plug-ins. According to one panelist's estimate, without such incentives, the market share of plug-ins won't reach 15 percent until 2035 or so.

But one challenge that's often overlooked involves building a new electricity-transmission infrastructure. As the refrain goes, plug-ins are only as green as the electricity grid; replacing gas-powered cars with coal-powered plug-ins isn't a real advance. If you're going to have a power grid where renewables play a prominent role, you're going to need a lot of new transmission lines, because most areas rich in renewable energy resources (particularly sunlight and wind) aren't very close to major population centers. And, unfortunately, so far it's been slow going. High Country News had a really terrific piece this month on the Los Angeles Department of Water and Power's plan to build new transmission lines to the city from geothermal fields near the Salton Sea, more than 100 miles to the southeast. Without these new transmission lines, Los Angeles will be unable to meet Mayor Antonio Villaraigosa's ambitious renewable-energy targets (20 percent of the city's power by 2010, and 35 percent by 2020).

But DWP--as well as San Diego's Sempra Energy, which wants to build a new Salton Sea transmission line too--is meeting fierce resistance, both from owners of property near the likely path of the transmission lines and from environmentalists who fear that the lines could threaten desert preserves. Old-fashioned NIMBYism, while deplorable, is at least to be expected. Opposition from environmentalists, on the other hand, is more aggravating, and it's hard to escape the conclusion that the movement is shooting itself in the foot. Now, there are a few complications to the story: Some environmentalists say they don't object to the basic concept, but would prefer an alternative route that spares important wildlife habitats. There are also allegations (which the utilities deny) that the lines are not really for renewable power in the first place, but for power from natural gas–fired plants in Baja California. But other greens obstinately refuse to countenance any new electricity infrastructure in the desert, which has frustrated Governor Arnold Schwarzenegger, who in April perceptively remarked to an audience at Yale, "If you can’t put solar panels in the Mojave Desert, where the hell can you put them?"

We'll have to wait and see what happens, but if even the mighty DWP can't overcome opposition from a handful of landowners and conservation groups, it'll be hard to be optimistic about new transmission lines being built anywhere. And without such lines, plug-in hybrids suddenly look a lot less attractive.

--Josh Patashnik 

Photo: Transmission lines near Big Morongo Canyon Preserve, Morongo Valley, Calif. Courtesy Getty Images