In order to give some prospective on scale of saving 1,500 megawatts of power during peak:

"California currently has around 2,300 MW of wind installed throughout the state"
ASX: AFG.AX) of Australia that will provide 1,500 megawatts (MW) or more of power, the largest wind energy contract ever signed by a U.S. utility.
...will involve the development of a wind farm on 50 square miles of land that Allco controls and or owns"
http://thefraserdomain.typepad.com/energy/2006/12/sce_signs_1500_.html

So, changing roof tiles, planting trees, changing the type of paving over a period 15 years [because this is average life of these sorts of things that require them to be changed] in one rather large city could get these types of power saving.

What is needed isn't draconian govt laws, instead what is needed is an increase in consumer awareness- the roof color/change of material saves the consumer money in terms their energy use and the further reduction to the community's energy bill is just gravy. There are hundreds of other cities this can also be applied to which could in total have somewhere 20 or more times the above 1500 megawatts in energy savings. In other something FAR more significant than all the alternative energy that Federal and State governments have been spending billions of dollar per year for last few decades.

And if done intelligently, it basically costs government no money, saves consumers billions of dollars, lower temperature during heatwaves and other more normal warm weather by 5-10 F. Lowers energy use, lowers the need to build as many powerplants to handle peak power demands, and lowers health costs significantly. And applied globally one probably easily times this by around another 5 times the effect.