Reduce our IT CO2 foot print, let's green label our applications!

After reading the book cradle to cradle I started thinking what we can do in IT about reducing our C02 footprint. People start to realize that IT is consuming some 5% of our energy consumption nowadays. So all hardware companies start thinking about how to improve the energy consumption of servers. This improvement is only aimed at the run time component of the application execution.
At design time, the question can be raised, can we make our programming greener?
I started programming in the late 80's, where I've learned to program to avoid memory usage (ok that lead us into the 2000 problem...), and optimize the program to run as smooth as possible with the scarce resources in mind.
With the ever increasing speed of processors, we are spoiled and tend to program sloppy nowadays, who cares about extra loop cycles, just add an extra processor.
Actually when we look nowadays at the 'size' of an application, the term SLOC (Source Lines of Code) is used. In short, instead of measuring the effectiveness of an application, we only look at the size, so size really matters....
Let's go back to the drawing table start thinking about programming again, how can we make our applications more efficient in the usage of resources?

I think green management of an application should be part of the design and run phase, and should already be added in the offerings we bring to our clients. Cars have an energy level, so why don't we green label our applications?