Before we get into this, I'm going to give the quick reveal right up top for you folks who don't like to read (or skim). For the best sun tea, don't bother with the sun.
'sun tea' on Serious Eats
Whether it's because you love the taste or because you're enjoying a thirst-inducing summer power outage, there's no funner way to make a good situation out of a heat wave than a jug of sun tea. Why even heat up so much as a kettle when Mother Nature will do it for you?