You could use the Web Site Copy Tool - deploying a web site using this tool only updates the files that have been changed.
After you connect to the remote site, each file will have one of the following statuses.
- Unchanged
- The file has not changed since the last time the file was copied.
- Changed
- The file has a timestamp that is newer than the timestamp taken when the file was last copied. If the same file has been changed in both the source site and the remote site and you synchronize these files, the tool prompts you to indicate in which direction you want to copy.
- New
- The file has been added since the last time the site was copied.
- Deleted
- The file has been removed since the last time the site was copied. These files are shown only if you select Show Deleted Files. If you synchronize a file that has been deleted in one site, the tool will prompt you to indicate if you want to delete the file from the other site.
See this article for further information