diff --git a/docs/source/usersguide/output/summary.rst b/docs/source/usersguide/output/summary.rst
index 6bf0cf2ad8..9ced8448a3 100644
--- a/docs/source/usersguide/output/summary.rst
+++ b/docs/source/usersguide/output/summary.rst
@@ -131,8 +131,8 @@ The current revision of the summary file format is 1.
 
 **/geometry/surfaces/surface <uid>/type** (*char[]*)
 
-    Type of the surface. Can be 'X Plane', 'Y Plane', 'Z Plane', 'Plane', 'X
-    Cylinder', 'Y Cylinder', 'Sphere', 'X Cone', 'Y Cone', or 'Z Cone'.
+    Type of the surface. Can be 'x-plane', 'y-plane', 'z-plane', 'plane',
+    'x-cylinder', 'y-cylinder', 'sphere', 'x-cone', 'y-cone', or 'z-cone'.
 
 **/geometry/surfaces/surface <uid>/coefficients** (*double[]*)
 
diff --git a/openmc/summary.py b/openmc/summary.py
index 3d7da115f6..2ae7464846 100644
--- a/openmc/summary.py
+++ b/openmc/summary.py
@@ -120,61 +120,61 @@ class Summary(object):
             coeffs = self._f['geometry/surfaces'][key]['coefficients'][...]
 
             # Create the Surface based on its type
-            if surf_type == 'X Plane':
+            if surf_type == 'x-plane':
                 x0 = coeffs[0]
                 surface = openmc.XPlane(surface_id, bc, x0, name)
 
-            elif surf_type == 'Y Plane':
+            elif surf_type == 'y-plane':
                 y0 = coeffs[0]
                 surface = openmc.YPlane(surface_id, bc, y0, name)
 
-            elif surf_type == 'Z Plane':
+            elif surf_type == 'z-plane':
                 z0 = coeffs[0]
                 surface = openmc.ZPlane(surface_id, bc, z0, name)
 
-            elif surf_type == 'Plane':
+            elif surf_type == 'plane':
                 A = coeffs[0]
                 B = coeffs[1]
                 C = coeffs[2]
                 D = coeffs[3]
                 surface = openmc.Plane(surface_id, bc, A, B, C, D, name)
 
-            elif surf_type == 'X Cylinder':
+            elif surf_type == 'x-cylinder':
                 y0 = coeffs[0]
                 z0 = coeffs[1]
                 R = coeffs[2]
                 surface = openmc.XCylinder(surface_id, bc, y0, z0, R, name)
 
-            elif surf_type == 'Y Cylinder':
+            elif surf_type == 'y-cylinder':
                 x0 = coeffs[0]
                 z0 = coeffs[1]
                 R = coeffs[2]
                 surface = openmc.YCylinder(surface_id, bc, x0, z0, R, name)
 
-            elif surf_type == 'Z Cylinder':
+            elif surf_type == 'z-cylinder':
                 x0 = coeffs[0]
                 y0 = coeffs[1]
                 R = coeffs[2]
                 surface = openmc.ZCylinder(surface_id, bc, x0, y0, R, name)
 
-            elif surf_type == 'Sphere':
+            elif surf_type == 'sphere':
                 x0 = coeffs[0]
                 y0 = coeffs[1]
                 z0 = coeffs[2]
                 R = coeffs[3]
                 surface = openmc.Sphere(surface_id, bc, x0, y0, z0, R, name)
 
-            elif surf_type in ['X Cone', 'Y Cone', 'Z Cone']:
+            elif surf_type in ['x-cone', 'y-cone', 'z-cone']:
                 x0 = coeffs[0]
                 y0 = coeffs[1]
                 z0 = coeffs[2]
                 R2 = coeffs[3]
 
-                if surf_type == 'X Cone':
+                if surf_type == 'x-cone':
                     surface = openmc.XCone(surface_id, bc, x0, y0, z0, R2, name)
-                if surf_type == 'Y Cone':
+                if surf_type == 'y-cone':
                     surface = openmc.YCone(surface_id, bc, x0, y0, z0, R2, name)
-                if surf_type == 'Z Cone':
+                if surf_type == 'z-cone':
                     surface = openmc.ZCone(surface_id, bc, x0, y0, z0, R2, name)
 
             # Add Surface to global dictionary of all Surfaces
diff --git a/src/summary.F90 b/src/summary.F90
index cc04599b0e..b93bf120c6 100644
--- a/src/summary.F90
+++ b/src/summary.F90
@@ -210,27 +210,27 @@ contains
       ! Write surface type
       select case (s%type)
       case (SURF_PX)
-        call write_dataset(surface_group, "type", "X Plane")
+        call write_dataset(surface_group, "type", "x-plane")
       case (SURF_PY)
-        call write_dataset(surface_group, "type", "Y Plane")
+        call write_dataset(surface_group, "type", "y-plane")
       case (SURF_PZ)
-        call write_dataset(surface_group, "type", "Z Plane")
+        call write_dataset(surface_group, "type", "z-plane")
       case (SURF_PLANE)
-        call write_dataset(surface_group, "type", "Plane")
+        call write_dataset(surface_group, "type", "plane")
       case (SURF_CYL_X)
-        call write_dataset(surface_group, "type", "X Cylinder")
+        call write_dataset(surface_group, "type", "x-cylinder")
       case (SURF_CYL_Y)
-        call write_dataset(surface_group, "type", "Y Cylinder")
+        call write_dataset(surface_group, "type", "y-cylinder")
       case (SURF_CYL_Z)
-        call write_dataset(surface_group, "type", "Z Cylinder")
+        call write_dataset(surface_group, "type", "z-cylinder")
       case (SURF_SPHERE)
-        call write_dataset(surface_group, "type", "Sphere")
+        call write_dataset(surface_group, "type", "sphere")
       case (SURF_CONE_X)
-        call write_dataset(surface_group, "type", "X Cone")
+        call write_dataset(surface_group, "type", "x-cone")
       case (SURF_CONE_Y)
-        call write_dataset(surface_group, "type", "Y Cone")
+        call write_dataset(surface_group, "type", "y-cone")
       case (SURF_CONE_Z)
-        call write_dataset(surface_group, "type", "Z Cone")
+        call write_dataset(surface_group, "type", "z-cone")
       end select
 
       ! Write coefficients for surface