diff --git a/services/core/java/com/android/server/EventLogTags.logtags b/services/core/java/com/android/server/EventLogTags.logtags
index d3ce306aa2427..6174aece39371 100644
--- a/services/core/java/com/android/server/EventLogTags.logtags
+++ b/services/core/java/com/android/server/EventLogTags.logtags
@@ -32,9 +32,11 @@ option java_package com.android.server
 # The device is being asked to go into a soft sleep (typically by the ungaze gesture).
 # It logs the time remaining before the device would've normally gone to sleep without the request.
 2731 power_soft_sleep_requested (savedwaketimems|2)
+# Power save state has changed. See BatterySaverController.java for the details.
+2739 battery_saver_mode (prevOffOrOn|1|5),(nowOffOrOn|1|5),(interactive|1|5),(features|3|5)
 
 #
-# Leave IDs through 2739 for more power logs (2730 used by battery_discharge above)
+# Leave IDs through 2740 for more power logs (2730 used by battery_discharge above)
 #
 
 
diff --git a/services/core/java/com/android/server/power/BatterySaverPolicy.java b/services/core/java/com/android/server/power/BatterySaverPolicy.java
index 3ccf17ee8c695..38101926c0d0e 100644
--- a/services/core/java/com/android/server/power/BatterySaverPolicy.java
+++ b/services/core/java/com/android/server/power/BatterySaverPolicy.java
@@ -86,6 +86,12 @@ public class BatterySaverPolicy extends ContentObserver {
     @GuardedBy("mLock")
     private String mDeviceSpecificSettingsSource; // For dump() only.
 
+    /**
+     * A short string describing which battery saver is now enabled, which we dump in the eventlog.
+     */
+    @GuardedBy("mLock")
+    private String mEventLogKeys;
+
     /**
      * {@code true} if vibration is disabled in battery saver mode.
      *
@@ -354,6 +360,27 @@ public class BatterySaverPolicy extends ContentObserver {
 
         mFilesForNoninteractive = (new CpuFrequencies()).parseString(
                 parser.getString(KEY_CPU_FREQ_NONINTERACTIVE, "")).toSysFileMap();
+
+        final StringBuilder sb = new StringBuilder();
+
+        if (mForceAllAppsStandby) sb.append("A");
+        if (mForceBackgroundCheck) sb.append("B");
+
+        if (mVibrationDisabled) sb.append("v");
+        if (mAnimationDisabled) sb.append("a");
+        if (mSoundTriggerDisabled) sb.append("s");
+        if (mFullBackupDeferred) sb.append("F");
+        if (mKeyValueBackupDeferred) sb.append("K");
+        if (!mFireWallDisabled) sb.append("f");
+        if (!mDataSaverDisabled) sb.append("d");
+        if (!mAdjustBrightnessDisabled) sb.append("b");
+
+        if (mLaunchBoostDisabled) sb.append("l");
+        if (mOptionalSensorsDisabled) sb.append("S");
+
+        sb.append(mGpsMode);
+
+        mEventLogKeys = sb.toString();
     }
 
     /**
@@ -431,6 +458,12 @@ public class BatterySaverPolicy extends ContentObserver {
         }
     }
 
+    public String toEventLogString() {
+        synchronized (mLock) {
+            return mEventLogKeys;
+        }
+    }
+
     public void dump(PrintWriter pw) {
         synchronized (mLock) {
             pw.println();
diff --git a/services/core/java/com/android/server/power/batterysaver/BatterySaverController.java b/services/core/java/com/android/server/power/batterysaver/BatterySaverController.java
index 1b19c33848cdd..a6bca0bf6c4ca 100644
--- a/services/core/java/com/android/server/power/batterysaver/BatterySaverController.java
+++ b/services/core/java/com/android/server/power/batterysaver/BatterySaverController.java
@@ -45,6 +45,7 @@ import com.android.internal.messages.nano.SystemMessageProto.SystemMessage;
 import com.android.internal.notification.SystemNotificationChannels;
 import com.android.internal.util.ArrayUtils;
 import com.android.internal.util.Preconditions;
+import com.android.server.EventLogTags;
 import com.android.server.LocalServices;
 import com.android.server.power.BatterySaverPolicy;
 import com.android.server.power.BatterySaverPolicy.BatterySaverPolicyListener;
@@ -77,6 +78,12 @@ public class BatterySaverController implements BatterySaverPolicyListener {
     @GuardedBy("mLock")
     private boolean mEnabled;
 
+    /**
+     * Previously enabled or not; only for the event logging. Only use it from
+     * {@link #handleBatterySaverStateChanged}.
+     */
+    private boolean mPreviouslyEnabled;
+
     private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
         @Override
         public void onReceive(Context context, Intent intent) {
@@ -213,12 +220,18 @@ public class BatterySaverController implements BatterySaverPolicyListener {
         final ArrayMap<String, String> fileValues;
 
         synchronized (mLock) {
-            Slog.i(TAG, "Battery saver " + (mEnabled ? "enabled" : "disabled")
-                    + ": isInteractive=" + isInteractive);
+            EventLogTags.writeBatterySaverMode(
+                    mPreviouslyEnabled ? 1 : 0, // Previously off or on.
+                    mEnabled ? 1 : 0, // Now off or on.
+                    isInteractive ?  1 : 0, // Device interactive state.
+                    mEnabled ? mBatterySaverPolicy.toEventLogString() : "");
+            mPreviouslyEnabled = mEnabled;
 
             listeners = mListeners.toArray(new LowPowerModeListener[mListeners.size()]);
+
             enabled = mEnabled;
 
+
             if (enabled) {
                 fileValues = mBatterySaverPolicy.getFileValues(isInteractive);
             } else {