So, there is a delivery fee. How do you save money by using a delivery service?
For starters, you will stick to what you ordered.
You won't see additional items while shopping in-store that you add to your cart. This all adds up.
Gas! If you live far from the place where you get your groceries, you will save on gas. I know I do!
Time! It saves time and it gives you time to do something else.
Here again, especially if you live far away from the store, you can save a lot of time by having your groceries delivered.