They save quite a bit of energy as the drying time is reduced by 30-40% or so. Woolzies also work better than plastic drier balls: I have noticed a marked difference in the quality and softness of the dried garments.
This product is efficient and environmentally friendly through and through: they’re made of pure wool so no plastic or other chemicals are used to make them. They drastically reduce the time required to dry clothing, they are gentler on the dried fabric, which also comes out softer and almost wrinkle-free. — Denis Zaff