Efficiency is troublesome when it comes to measuring..

As an example:

Last Feburary, i bought a 1999 Chevy S10 with 70,000 miles on it. I get about 25 MPG.

While not as efficient as a newer vehicle, the energy and pollution costs of manufacturing it has already been expended.

The energy and pollution expense of producing a new car is only slightly less than it was for my older vehicle, but you would also need to account for the energy and pollution expense of recycling my older vehicle.

By keeping my older, less efficient vehicle, I can spend less money, be less polluting and use less energy.

A similar problem can be said for energy efficient light bulbs.

High consumpton incandescent bulbs may be "less efficient" when it comes to producing light, but during the winter the heat they release reduces the energy required to heat a home conventionally.

A more practical, long term view of efficiency would be beneficial in reduction of consumption.