Place the sugar and water in a saucepan. Wash and dry the lemons. Slice one of the lemons and juice the remaining 3. Add the lemon slices to water and sugar and set the lemon juice aside.
Wash and dry the ginger. Cut it into slices and add it to the sugar and water in the saucepan.
Place the saucepan over medium heat and bring it to boil. Simmer for 10 minutes. Turn the heat off, cover the saucepan and let it sit for 30 minutes.
Discard the ginger and lemon slices. Pour the syrup into a pitcher and add the lemon juice.
Add 4 cups of water and stir the lemonade. Taste and add more water if needed. Serve in glasses over ice.
Notes
Instead of sugar, you can use honey or maple syrup.
You can add mint, rosemary or lavender to the lemon sliced and ginger while simmering.
To make sparkling ginger lemonade add sparkling water instead of still water.