File transfer speed is very low. WinSCP does not utilize all available bandwidth. How do I improve the transfer speed?

File transfers in WinSCP are encrypted and encryption is CPU intensive. Either your local workstation or your server might not be able to encrypt file transfer stream at the same speed, your connection is able to transfer it. You may try to choose different encryption algorithm on Login dialog. Also SSH-1 is in general less CPU intensive than SSH-2. SCP protocol is usually faster than SFTP too.