diff --git a/CHANGES/1170.misc.rst b/CHANGES/1170.misc.rst
new file mode 100644
index 00000000..9f27309d
--- /dev/null
+++ b/CHANGES/1170.misc.rst
@@ -0,0 +1 @@
+Improved performance of converting :class:`~yarl.URL` to a string when no explicit port is set -- by :user:`bdraco`.
diff --git a/tests/test_url.py b/tests/test_url.py
index 49245b8d..9947b950 100644
--- a/tests/test_url.py
+++ b/tests/test_url.py
@@ -304,35 +304,43 @@ def test_port_for_implicit_port():
 def test_port_for_relative_url():
     url = URL("/path/to")
     assert url.port is None
+    assert url._port_not_default is None
+    assert url.explicit_port is None
 
 
 def test_port_for_unknown_scheme():
     url = URL("unknown://example.com")
     assert url.port is None
+    assert url._port_not_default is None
+    assert url.explicit_port is None
 
 
 def test_explicit_port_for_explicit_port():
     url = URL("http://example.com:8888")
     assert 8888 == url.explicit_port
     assert url.explicit_port == url._val.port
+    assert url._port_not_default == 8888
 
 
 def test_explicit_port_for_implicit_port():
     url = URL("http://example.com")
     assert url.explicit_port is None
     assert url.explicit_port == url._val.port
+    assert url._port_not_default is None
 
 
 def test_explicit_port_for_relative_url():
     url = URL("/path/to")
     assert url.explicit_port is None
     assert url.explicit_port == url._val.port
+    assert url._port_not_default is None
 
 
 def test_explicit_port_for_unknown_scheme():
     url = URL("unknown://example.com")
     assert url.explicit_port is None
     assert url.explicit_port == url._val.port
+    assert url._port_not_default is None
 
 
 def test_raw_path_string_empty():
diff --git a/yarl/_url.py b/yarl/_url.py
index 3f3a6d9f..bac600d7 100644
--- a/yarl/_url.py
+++ b/yarl/_url.py
@@ -603,10 +603,10 @@ def _default_port(self) -> Union[int, None]:
     @cached_property
     def _port_not_default(self) -> Union[int, None]:
         """The port part of URL normalized to None if its the default port."""
-        port = self.port
-        if self._default_port == port:
+        explicit_port = self.explicit_port
+        if explicit_port is None or explicit_port == self._default_port:
             return None
-        return port
+        return explicit_port
 
     @cached_property
     def authority(self) -> str: