diff --git a/RELEASE_NOTES.md b/RELEASE_NOTES.md
index 3ccdc5ff..21264538 100644
--- a/RELEASE_NOTES.md
+++ b/RELEASE_NOTES.md
@@ -26,6 +26,10 @@
   `METRIC_AC_APPARENT_CURRENT` -> `METRIC_AC_CURRENT`
   `METRIC_AC_APPARENT_CURRENT_PHASE_[1|2|3]` -> `METRIC_AC_CURRENT_PHASE_[1|2|3]`
 
+- Metrics for Total Harmonic Distortion have been un-abbreviated:
+  `METRIC_AC_THD_CURRENT` -> `METRIC_AC_TOTAL_HARMONIC_DISTORTION_CURRENT`
+  `METRIC_AC_THD_CURRENT_PHASE_[1|2|3]` -> `METRIC_AC_TOTAL_HARMONIC_DISTORTION_CURRENT_PHASE_[1|2|3]`
+
 ## New Features
 
 - Added a `Frequenz.api.common.v1.types.Decimal` type, compatible with
diff --git a/proto/frequenz/api/common/v1/metrics/metric_sample.proto b/proto/frequenz/api/common/v1/metrics/metric_sample.proto
index 66069a75..553a0a2a 100644
--- a/proto/frequenz/api/common/v1/metrics/metric_sample.proto
+++ b/proto/frequenz/api/common/v1/metrics/metric_sample.proto
@@ -129,10 +129,10 @@ enum Metric {
   METRIC_AC_REACTIVE_ENERGY_PHASE_3 = 70;
 
   // AC harmonics
-  METRIC_AC_THD_CURRENT = 80;
-  METRIC_AC_THD_CURRENT_PHASE_1 = 81;
-  METRIC_AC_THD_CURRENT_PHASE_2 = 82;
-  METRIC_AC_THD_CURRENT_PHASE_3 = 83;
+  METRIC_AC_TOTAL_HARMONIC_DISTORTION_CURRENT = 80;
+  METRIC_AC_TOTAL_HARMONIC_DISTORTION_CURRENT_PHASE_1 = 81;
+  METRIC_AC_TOTAL_HARMONIC_DISTORTION_CURRENT_PHASE_2 = 82;
+  METRIC_AC_TOTAL_HARMONIC_DISTORTION_CURRENT_PHASE_3 = 83;
 
   // General BMS metrics.
   METRIC_BATTERY_CAPACITY = 101;