The ACH system is one of the most robust payments systems in the world and is responsible for over $40 Trillion in payments every year. ACH payments typically require 3-5 business days to process in order to ensure that your account has sufficient funds.
In order to facilitate electronic funds transfers between two accounts, your funds will move from the source account (e.g. checking account) to your Dwolla account for a short time (3-5 days) and then to the destination account (e.g., savings account). We would love to help you move funds instantly from one bank to the other but unfortunately the payments systems in the US are not set up for this scenario yet.