To get the reduced amount of CO2 savings not being released to the atmosphere,
multiply the #kWh saved times 1.5 lbs/kWh. So for example, each 14watt CFL would save 690
pounds over the life of the bulb; 9 bulbs would save 6210 pounds or over 3 tons! (if we use oil or coal to produce electricity).
http://www.nwcouncil.org/comments/calcs.asp
With an assortment of calculators, including a streetlight savings calc.