But perhaps the greatest obstacle to the wider adoption of wind power is the need to overhaul the power grid to accommodate it. Transmitting wind power from rural areas with strong winds to populated areas with high demand will require expensive new transmission lines. In addition, the power grid must become more flexible, though some progress has already been made. “Although wind is variable, it is also very predictable,” explains Andrew Garrad, the boss of Garrad Hassan, a consultancy in Bristol, England. Wind availability can now be forecast over a 24-hour period with a reasonable degree of accuracy, making it possible to schedule wind power, much like conventional power sources.Still, unlike electricity from traditional sources, wind power is not always available on demand. As a result, grid operators must ensure that reserve sources are available in case the wind refuses to blow. But because wind-power generation and electricity demand both vary, the extra power reserves needed for a 20% share of wind are actually fairly small—and would equal only a few percent of the installed wind capacity, says Edgar DeMeo, co-chair of the 20% wind advisory group for America’s Department of Energy.