Most of the saving from reduced energy usage have already been realized and any additional benefits are not economically justified even at higher prices. If you have a car that gets 40 MPG and you drive 5,000 miles per year buying a car that gets 50 MPG will only save you 100 gals. At $10 dollars per gal you save only $1,000 so if you keep the car for 5 years you save $5,000 and if the car costs more than $5,000 more than a car that gets 40 MPG then its not worth it. the same logic applies to all uses of energy and after decades of looking at reduced energy the additional sames are now minimal — unless you give up performance!