These are definitely blackout panels and they keep out the heat... Wayfair even sent us two panels the wrong size so we just have one panel on each window for now, (exchange pending) but still NO SUN comes through with just one panel and makes a huge difference in the temperature (we live in the hot desert and used these in a part of the house where the hottest afternoon sun hits for a good chunk of the day). Thanks for saving us on our AC bill!!