Burning CPU cycles
How about Energy Star project timelines? When server apps are up to millions of lines of code, it's common to see a system gain 100% to 1000% more throughput after old architectural problems are fixed. That's a lot more power saved than you'll get from fine tuning a server's power supply. From a business point of view, the power and hardware savings from code optimization usually don't compare well to the same effort spent on building new services. Power is cheap, today's servers are losing value, and tomorrow's servers will be faster.