It might be useful to give some back story on the intent of estimates within Intervals since there are project estimates and task estimates. The most common way is to use the project estimates to set the high level budget for the project and then use the task estimates as a control/reality check for the project. It is a top down vs. bottom up view. On the Pelago web development side of our business we sell contacts that have the total number of hours included for the project then use the task estimates as an early indicator if the project is going to go over what was contracted. The estimated vs. actual link in the left hand column for an individual project is probably worth a look to view an individual project. There are toggles to view by the project's estimated work or by the task estimates.
If you are more interested in seeing hours only based on task estimates:
On the task listing if you filter for an individual project the estimates will total up on the listing. Selecting “include closed tasks” at the top of the listing will include all tasks for the project. This can be filtered for individual resources as well.
If you navigate into a project and then click on estimated vs. actual there is a link to toggle task estimates.
In the reporting section if you run a project activity report and select “by task” in the summary drop down the bottom half of the report will include all tasks and their estimated time. This report can be filtered by person as well.
In the reporting section if you run the project landscape report and click on the time tab after the report is generated the total task estimates are included.
Depending on your workflow and the data you need one of those might be an option. The project landscape report is probably the most comprehensive report for project related budget and time information.