John Handra shows how to configure read-only routing on an Availability Group:
NOTE: SQL Server 2016 introduces load-balancing across the secondary replicas in your AlwaysOn Availability Group. To utilize this feature, the above routing list will need to be modified so that SQL Server directs incoming read-only connections across the servers you choose to be load-balanced. You will have to use nested parentheses around the server instances you want to be part of the load-balanced group.
Read-only routing requires some additional setup and possibly load changes, but it can give you a nice performance gain by off-loading some of your read requests.