diff --git a/Changelog.md b/Changelog.md
index efd9869fb..0f84f68d1 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -1,3 +1,10 @@
+# v0.11.28
+
+* Change to report efficiency instead of overhead.
+  Efficiency is defined by `killtime / runtime`.
+
+  [#1415](https://github.com/mbj/mutant/pull/1415)
+
 # v0.11.27 2023-12-01
 
 * [#1414](https://github.com/mbj/mutant/pull/1414)
diff --git a/lib/mutant/reporter/cli/printer/env_progress.rb b/lib/mutant/reporter/cli/printer/env_progress.rb
index a3e8bf804..d4e3d9cdc 100644
--- a/lib/mutant/reporter/cli/printer/env_progress.rb
+++ b/lib/mutant/reporter/cli/printer/env_progress.rb
@@ -14,7 +14,6 @@ class EnvProgress < self
             :coverage,
             :env,
             :killtime,
-            :overhead,
             :runtime
           )
 
@@ -25,7 +24,7 @@ class EnvProgress < self
             [:info,   'Timeouts:        %s',      :amount_timeouts        ],
             [:info,   'Runtime:         %0.2fs',  :runtime                ],
             [:info,   'Killtime:        %0.2fs',  :killtime               ],
-            [:info,   'Overhead:        %0.2f%%', :overhead_percent       ],
+            [:info,   'Efficiency:      %0.2f%%', :efficiency_percent     ],
             [:info,   'Mutations/s:     %0.2f',   :mutations_per_second   ],
             [:status, 'Coverage:        %0.2f%%', :coverage_percent       ]
           ].each(&:freeze)
@@ -50,8 +49,8 @@ def coverage_percent
             coverage * 100
           end
 
-          def overhead_percent
-            (overhead / killtime) * 100
+          def efficiency_percent
+            (killtime / runtime) * 100
           end
         end # EnvProgress
       end # Printer
diff --git a/lib/mutant/reporter/cli/printer/status_progressive.rb b/lib/mutant/reporter/cli/printer/status_progressive.rb
index 862d4a7e5..465f34931 100644
--- a/lib/mutant/reporter/cli/printer/status_progressive.rb
+++ b/lib/mutant/reporter/cli/printer/status_progressive.rb
@@ -14,7 +14,6 @@ class StatusProgressive < self
             :amount_mutations_alive,
             :amount_mutations_killed,
             :killtime,
-            :overhead,
             :runtime
           )
 
diff --git a/lib/mutant/result.rb b/lib/mutant/result.rb
index f701210fa..b6dd11dd9 100644
--- a/lib/mutant/result.rb
+++ b/lib/mutant/result.rb
@@ -50,17 +50,6 @@ def delegate(name, target)
 
     private_constant(*constants(false))
 
-    # Mutant overhead running mutatet tests
-    #
-    # This is NOT the overhead of mutation testing, just an engine specific
-    # measurement for the efficiency of the parallelization engine, kill
-    # isolation etc.
-    #
-    # @return [Float]
-    def overhead
-      runtime - killtime
-    end
-
     # Hook called when module gets included
     #
     # @param [Class, Module] host
diff --git a/spec/unit/mutant/reporter/cli/printer/env_progress_spec.rb b/spec/unit/mutant/reporter/cli/printer/env_progress_spec.rb
index 449b89544..a66a26b0a 100644
--- a/spec/unit/mutant/reporter/cli/printer/env_progress_spec.rb
+++ b/spec/unit/mutant/reporter/cli/printer/env_progress_spec.rb
@@ -29,7 +29,7 @@
         Timeouts:        0
         Runtime:         4.00s
         Killtime:        0.00s
-        Overhead:        Inf%
+        Efficiency:      0.00%
         Mutations/s:     0.00
         Coverage:        100.00%
       STR
@@ -56,7 +56,7 @@
         Timeouts:        0
         Runtime:         4.00s
         Killtime:        2.00s
-        Overhead:        100.00%
+        Efficiency:      50.00%
         Mutations/s:     0.50
         Coverage:        100.00%
       STR
@@ -85,7 +85,7 @@
         Timeouts:        0
         Runtime:         4.00s
         Killtime:        2.00s
-        Overhead:        100.00%
+        Efficiency:      50.00%
         Mutations/s:     0.50
         Coverage:        50.00%
       STR
diff --git a/spec/unit/mutant/reporter/cli/printer/env_result_spec.rb b/spec/unit/mutant/reporter/cli/printer/env_result_spec.rb
index 4ae5cb73e..28ca9e72a 100644
--- a/spec/unit/mutant/reporter/cli/printer/env_result_spec.rb
+++ b/spec/unit/mutant/reporter/cli/printer/env_result_spec.rb
@@ -36,7 +36,7 @@
       Timeouts:        0
       Runtime:         4.00s
       Killtime:        2.00s
-      Overhead:        100.00%
+      Efficiency:      50.00%
       Mutations/s:     0.50
       Coverage:        50.00%
     STR
diff --git a/spec/unit/mutant/reporter/cli_spec.rb b/spec/unit/mutant/reporter/cli_spec.rb
index 0714456a5..e34a6d493 100644
--- a/spec/unit/mutant/reporter/cli_spec.rb
+++ b/spec/unit/mutant/reporter/cli_spec.rb
@@ -99,7 +99,7 @@ def self.it_reports(expected_content)
       Timeouts:        0
       Runtime:         4.00s
       Killtime:        2.00s
-      Overhead:        100.00%
+      Efficiency:      50.00%
       Mutations/s:     0.50
       Coverage:        100.00%
     REPORT
diff --git a/spec/unit/mutant/result_spec.rb b/spec/unit/mutant/result_spec.rb
index 4039711f3..a1b6f8eab 100644
--- a/spec/unit/mutant/result_spec.rb
+++ b/spec/unit/mutant/result_spec.rb
@@ -22,12 +22,4 @@ def collection
       expect(object.length).to be(1)
     end
   end
-
-  describe '#overhead' do
-    subject { object.overhead }
-
-    it 'returns difference between runtime and killtime' do
-      should eql(2.0)
-    end
-  end
 end