* doc/guix.texi (Invoking `guix size'): Add guix size example for store item.
the closure is not a problem @i{per se} because they are always available
on the system anyway.)
+Since the command also accepts store file names, assessing the size of
+a build result is straightforward:
+
+@example
+guix size $(guix system build config.scm)
+@end example
+
When the package(s) passed to @command{guix size} are available in the
store@footnote{More precisely, @command{guix size} looks for the
@emph{ungrafted} variant of the given package(s), as returned by