Hello,
This is Ann from European Rolling Shutters. Our company and website was mentioned in this thread.
There have been a couple independent studies that estimate savings from exterior rolling shutters or shades (screens). The savings vary depending on the price, quality, type of window, type of window attachment and so on.
PAMA did a study that found exterior solar shades can reduce annual cooling energy costs up to 86% for homes in San Francisco.
Here is the excerpt from that study for San Francisco (sorry, can't find the entire study at the moment):
http://www.ersshading.com/images/news/solar-shades-study-CA_San_Francisco_PAMA.pdf
The AERC (Attachments Energy Rating Council) also recently published this utility study very recently that covers blinds, cellular shades, roller shades, solar screens and storm windows.
http://aercnet.org/wp-content/uploads/2016/10/UtilityInfo.pdf
And you can REALLY geek out over stats in this Berkeley Labs study done for Energy.gov where they ran 16,848 energy simulations for 12 climate zones, four house types, three baseline windows, 11 window attachment categories, four attachment qualities and varying number of deployment positions.
http://energy.gov/sites/prod/files/2013/11/f5/energy_savings_from_windows_attachments.pdfHope that helps!