Trying to trim costs

So today we put up some Gila Heat Control Titanium Film on our sliding glass doors that get direct afternoon sun.  This afternoon it was pretty amazing how much cooler the living room is versus how it normally is.  The film itself has a slight tint; probably not any more than you would find on a new car window.  I purchased the film at one of the big box home supply places for $35.  Considering the power bill for 6/18-7/18 was $232, I am hoping to see at least a small reduction in costs.  I'll let you know in about 20 days.