S.K.
We have "double cell" cellular shades and they work great. Our eating area in the kitchen gets really hot and when I close the shade, it makes a huge difference. It isn't room darkening because I like some light coming through. In our playroom we went a little cheaper and got single cell shades and I regret it. They help but it still gets too warm in there. We put the film on the back
door in there and it didn't do much plus it was a HUGE pain to put it on because we didn't want any bubbling. Almost impossible.
My brother and his wife bought the solar screens for their old house and they said it made a huge difference. Not sure on the price but I know they were pretty high.