If you’re chosen to donate, someone else is not, so they save time, although overall, more time is wasted if you don’t sign up, because the organization will have to deal with an extra potential donor. Roughly one more person will be signed up in expectation if you sign up, unless you think you have an important effect on others. You’re not wasting the time of anyone else who signed up if you sign up, since they were already going to pay that cost.
If you’re not chosen to donate, you’ll waste your own time, and the time of the organization.
Overall, though, if you’re EA-minded, your time is probably worth much more than the average person who signed up, and I think this should dominate time considerations.
If you’re chosen to donate, someone else is not, so they save time, although overall, more time is wasted if you don’t sign up, because the organization will have to deal with an extra potential donor. Roughly one more person will be signed up in expectation if you sign up, unless you think you have an important effect on others. You’re not wasting the time of anyone else who signed up if you sign up, since they were already going to pay that cost.
If you’re not chosen to donate, you’ll waste your own time, and the time of the organization.
Overall, though, if you’re EA-minded, your time is probably worth much more than the average person who signed up, and I think this should dominate time considerations.