Add 4 cups of water to a saucepan over medium-high heat. Bring to a boil. Remove from heat. After water has stopped boiling, add tea bags and steep for 5 minutes. Remove tea bags from water.
Add sugar and stir until dissolved.
Pour tea concentrate into a 1-gallon pitcher and top with remaining 12 cups of water. Stir to combine.
Refrigerate for 2-3 hours, or until chilled. Serve over ice.
Notes
Sweeten to preference: For less sweet tea, start with ½ to ⅔ cup of sugar. For sweeter tea, add up to 1.5 cups of sugar total.
Storage: Sweet tea has the best flavor within 1 day of preparing, but will keep for 3-4 days before flavor starts to taste "off".
Garnish options: Add lemon/orange slices or fresh mint to glasses before serving.