There is tons of data to show that engaged employees create engaged customers. Consider this about engaged employees:

1. Always try their hardest at work.
2. Stay late to work if something needs to be done after the normal workday ends.
3. Do something good for the company even if it isn’t expected of them.
4. Make a recommendation for an improvement.
5. Recommend a friend or relative apply for a job.

And the list goes on.

via The Untapped Value of Employee Engagement Infographic | Customer Experience Matters.