A new study by the Oak Ridge National Laboratory looked at the impact that plug-in hybrids (and indirectly, electric cars) might have on the US electricity grid in the next few decades. They found that, as they say, timing is everything: If the cars were recharged after 10 P.M. there might not be a need for new power plants (in their "high-demand" scenario, 8 new plants are required).
This means that we would get the net benefit from the removal of all these gasoline and diesel vehicles without much more pollution coming from the grid. Actually, we hope that by that time any new generation built will be clean (wind, wave, solar, geothermal, etc).What if the timing was bad? The researchers looked at what would happen if all these vehicles were plugged in at 5 P.M. (at 6 kW of power on average, with a 25 percent market penetration by 2020) and found that up to 160 new power plants would have to be built. That might still make sense if many of those are clean and if it means millions less fossil-fuel powered cars on the road (someone would have to do the math), but it definitely would be sub-optimal.
Of course, we can't assume that people would plug their cars at night without any incentives or ways to balance out the inconvenience, but we don't think that would be a show-stopper.
Smart-metering could make the electricity rates vary almost in real time based on the supply-demand situation, and programmable chargers could be set to only charge cars between certain hours, or when rates are below a certain level. You wouldn't need to get up late at night and manually go plug the car; just plug it whenever, and the charger will do the rest.
Fully electric cars would of course need more power than plug-ins, but by using smart-charging and smart-metering we could use the power that we already have more efficiently. For example, have cars start charging whenever we're producing more than we're using (day or night). This might be a very windy or sunny day and wind and solar farms are producing more power than can be used.
Of course at some point new power generation will be needed, but if it is clean and internal combustion cars are replaced, it could still be a big gain.
See also: ::OEMtek Turns Hybrids into Plug-in Hybrids, ::BYD F6DM: Will the First Plug-In Hybrid be Chinese?, ::GM's Chevy Volt Price Goes Up; Stereo, Wipers to Blame, ::How's The Google Plug-In Hybrid Fleet Doing?