Will SSL Encryption slow down page load? If so, how do I estimate the impact on performance for my web application?
This is a possible duplicate of several questions:
The last includes this answer, including: "non-SSL sockets are less than 10 times faster than SSL sockets". However, this can be a bit misleading - be sure to read the entire answer.
You can also mitigate the performance concern, at least on the server-side, by offloading the SSL processing to another device, e.g. a dedicated load balancer or firewall.