Thanks Kyna and hello Sara,
Although it's possible that the new Reporting 2.0 functionality might help with this one, it's still a ways out, so other than the two workarounds the support team mentioned, the only (kinda) out of the box alternative I can suggest would be a relatively simple API report that you could type into a url (providing the Project ID) that returns the total (sparing you the Excel export / tally). Alternatively, I invite you to consider Fusion or our UberCalc solution, with which you could use to rollup-and-store the total you're after at the Project level.
Regards,
Doug