Energy efficiency refers to approaches or strategies that yield more service value from each primary energy consumed.
Making homes, vehicles, and businesses more energy efficient is seen as a largely untapped solution to addressing the problems of pollution, global warming, energy security, and fossil fuel depletion.
Via Lauren Moss
In areas of dense population, we should concentrate our efforts toward green and energy efficiency. Any improvement in energy efficiency would be compounded by the number of people this would be available to. That woould increase the cost effictiveness and impact on the planet quickly.