As a follow-up note, We have a 2 story-home with many windows facing WEST.
We tinted all of the WEST windows with 60-80% blockage.
Wow, what a difference!
Electricity bill went down 25%:
June 2005: $230 (avergae 90-100 deg F)
June 2006: $180 (everage 95-105 deg F)
I strongly recommend Tinting windows, especially those facing WEST.