You may separate your whites from colors when you wash your clothes, but when it comes to drying them, separate according to weight. By drying heavy clothes like jeans, sweaters and thick flannel shirts separately from light fabrics like T-shirts and undergarments, you will be using the least amount of energy. Start by drying a load of light fabrics first; they will dry quickly and warm up the inside of the dryer. Then add the heavier items for a second load. The residual heat from the first load will help speed up that drying process. Since modern dryers have moisture sensors, it will automatically and accurately turn off when the batch of clothes are truly dry and ready to be removed.