These curtains definitely do the job as long as they physically cover the entire window, ie, yes, sunlight will sneak out of the corners that the curtain does not cover. I live in NYC on a very, very brightly lit street, so, if they help me, they will probably help you. They also block out a bit of the wind that comes through the window. Can't comment on the heat that might come through. They are heavy/dense curtains and not flimsy (which I was scared of). The creasing hasn't naturally gotten out since I've hung them (2+ months) and I intend to iron it out so it doesn't look like I just pulled them out of the package. Also, the stitching isn't perfect, but price v. quality is fantastic. they also come with ties so you can pull them together. Overstock shipped me the wrong size, the longer one (they just skim the floor), than I ordered, but it actually turned out for the better for me as I plan on keeping these curtains for a long time. They do look luxious & make a statement (I ordered them in Black/Pewter) and look as they do in the picture.