Sweet oranges are the ones you know and love from the supermarket, the kind whose juice drips down your chin. The peel of the sweet orange delivers a more positively identifiable orange character to beer than does that of the bitter orange. A popular member of the sweet orange family, the Valencia (Citrus sinensis var._ Valencia_) is the signature variety found in Blue Moon Belgian White. If you enjoy this kind of flavor, then sweet orange peel is the way to go.
Sweet orange peel is popular in holiday beers and pairs well with other holiday spices such as cloves and cinnamon.
So there you go. Use bitter orange peel for a pleasant citrusy character and sweet orange peel for intense orange flavor. Regardless which you choose, start small and adjust your recipe to taste. Add 0.5–1.0 ounce (14–28 grams) of dried orange peel 5 to 15 minutes before the end of the boil, or steep in hot water for 10 minutes and add to secondary.
This can also be used as a botanical in gin distilling, just experiment away.....