diff --git a/README.md b/README.md
index d7fbb31..6a2040f 100644
--- a/README.md
+++ b/README.md
@@ -60,15 +60,21 @@ click a number to edit it (turn changes it, click confirms), hold to go back.
 Entries:
 
 * **Save as favourite / Remove from favourites** — the camera that was playing;
-  saving asks for one of the 12 slots (overwrites it).
-* **Favourites** — the 12 slots; click one to play it. A saved camera shows a
+  saving asks for one of the 24 slots (overwrites it).
+* **Favourites** — the 24 slots; click one to play it. A saved camera shows a
   yellow *FAV n* marker while it plays.
 * **Source** — *Random* draws from the sites, *Favourites* cycles the saved slots.
 * **Provider** — *insecam*, *opentopia* or *Mixed* (a random site per batch).
 * **Time per camera**, **Listing** (mixed / top rated / newest), **Screen
   brightness**, **Ring brightness**, **Caption**.
-* **Forget a favourite**, **Wi-Fi setup** (reboots into the hotspot), the board
-  name with its IP, and the power source.
+* **Forget a favourite**, **Wi-Fi setup** (reboots into the hotspot), **Power
+  off**, the board name with its IP, and the power source.
+
+*Power off* switches the peripheral rail off (screen, ring, codec) and puts the
+ESP32-S3 into deep sleep; turning the knob wakes it and it boots as normal. The
+encoder's push button is deliberately not a wake source: it is GPIO 0, and a
+press that is still held when the chip resets would land it in the ROM
+bootloader instead.
 
 The menu closes by itself after 45 s without input.
 
@@ -114,8 +120,9 @@ it stays out of the way. The CC1101 board's BQ27220 gauge is not supported.
   elapses or the knob moves, skip dead cameras, keep history for "previous".
 * `ui.c` is LVGL 9 via `esp_lvgl_port`: a canvas for the frame, a translucent
   caption bar, a LIVE/PAUSED badge, a hairline progress bar and a six-row menu page.
-* `settings.c` keeps the settings blob and the 12 favourite slots in NVS
-  (namespace `widget`); `menu.c` is the knob-driven menu that edits them.
+* `settings.c` keeps the settings blob and the 24 favourite slots in NVS
+  (namespace `widget`); `menu.c` is the knob-driven menu that edits them;
+  `power.c` is the deep-sleep power-off with ext1 wake on the encoder pins.
 
 ## License
 
diff --git a/main/CMakeLists.txt b/main/CMakeLists.txt
index edc0b8f..48a5244 100644
--- a/main/CMakeLists.txt
+++ b/main/CMakeLists.txt
@@ -1,6 +1,6 @@
 idf_component_register(
     SRCS "main.c" "board.c" "display.c" "ui.c" "leds.c" "input.c" "net.c"
-         "httpstream.c" "jpegframe.c" "jpegdec.c" "insecam.c" "slideshow.c" "settings.c" "menu.c" "battery.c" "webpage.c" "opentopia.c"
+         "httpstream.c" "jpegframe.c" "jpegdec.c" "insecam.c" "slideshow.c" "settings.c" "menu.c" "battery.c" "webpage.c" "opentopia.c" "power.c"
     INCLUDE_DIRS "."
     PRIV_REQUIRES esp_lcd esp_wifi nvs_flash esp_netif esp_event esp_http_server driver esp_timer esp_adc esp_http_client mbedtls
 )
diff --git a/main/display.c b/main/display.c
index 356bae1..6c8c5f2 100644
--- a/main/display.c
+++ b/main/display.c
@@ -15,6 +15,8 @@ static const char *TAG = "display";
 #define BL_TIMER LEDC_TIMER_0
 #define BL_CHANNEL LEDC_CHANNEL_0
 
+static esp_lcd_panel_handle_t panel;
+
 static void backlight_init(void)
 {
     ledc_timer_config_t timer = {
@@ -57,7 +59,6 @@ void display_init(void)
     };
     ESP_ERROR_CHECK(esp_lcd_new_panel_io_spi((esp_lcd_spi_bus_handle_t)LCD_SPI_HOST, &io_cfg, &io));
 
-    esp_lcd_panel_handle_t panel = NULL;
     esp_lcd_panel_dev_config_t panel_cfg = {
         .reset_gpio_num = board->lcd_rst,
         .rgb_ele_order = board->lcd_bgr ? LCD_RGB_ELEMENT_ORDER_BGR : LCD_RGB_ELEMENT_ORDER_RGB,
@@ -90,3 +91,9 @@ void display_init(void)
     if (!disp) { ESP_LOGE(TAG, "lvgl_port_add_disp failed"); abort(); }
     ESP_LOGI(TAG, "ST7789 %dx%d up at %d MHz", LCD_H_RES, LCD_V_RES, CONFIG_WIDGET_LCD_PCLK_MHZ);
 }
+
+void display_off(void)
+{
+    display_set_backlight(0);
+    if (panel) esp_lcd_panel_disp_on_off(panel, false);
+}
diff --git a/main/display.h b/main/display.h
index 3f5c52d..49efe32 100644
--- a/main/display.h
+++ b/main/display.h
@@ -8,3 +8,5 @@
 void display_init(void);
 // 0..100
 void display_set_backlight(uint8_t percent);
+// Panel sleep-in (used before powering down).
+void display_off(void);
diff --git a/main/main.c b/main/main.c
index da087e8..ccf52f1 100644
--- a/main/main.c
+++ b/main/main.c
@@ -5,6 +5,7 @@
 #include "jpegdec.h"
 #include "leds.h"
 #include "net.h"
+#include "power.h"
 #include "settings.h"
 #include "slideshow.h"
 #include "ui.h"
@@ -29,6 +30,7 @@ static void run_portal(void)
 void app_main(void)
 {
     board_init();
+    power_report_wakeup();
     settings_init();
     leds_init();
     leds_set_brightness(settings.led_brightness);
diff --git a/main/menu.c b/main/menu.c
index 8dbf64a..e15fddd 100644
--- a/main/menu.c
+++ b/main/menu.c
@@ -5,6 +5,7 @@
 #include "input.h"
 #include "leds.h"
 #include "net.h"
+#include "power.h"
 #include "settings.h"
 #include "ui.h"
 #include "esp_log.h"
@@ -19,7 +20,7 @@ static const char *TAG = "menu";
 
 typedef enum { VIEW_TOP, VIEW_FAV_PLAY, VIEW_FAV_SAVE, VIEW_FAV_FORGET } view_t;
 enum { ROW_FAV_TOGGLE, ROW_FAVS, ROW_SOURCE, ROW_PROVIDER, ROW_INTERVAL, ROW_LISTING, ROW_LCD, ROW_RING,
-       ROW_CAPTION, ROW_FORGET, ROW_WIFI, ROW_IP, ROW_BATTERY, ROW_CLOSE, TOP_ROWS };
+       ROW_CAPTION, ROW_FORGET, ROW_WIFI, ROW_POWER, ROW_IP, ROW_BATTERY, ROW_CLOSE, TOP_ROWS };
 
 static ui_menu_row_t rows[TOP_ROWS > FAV_SLOTS + 1 ? TOP_ROWS : FAV_SLOTS + 1];
 static char values[TOP_ROWS][20];
@@ -52,6 +53,7 @@ static int build_top(const cam_info_t *current, int fav_slot)
     rows[ROW_CAPTION] = (ui_menu_row_t){"Caption", settings.caption ? "Shown" : "Hidden", false};
     rows[ROW_FORGET] = (ui_menu_row_t){"Forget a favourite", NULL, fav_count() == 0};
     rows[ROW_WIFI] = (ui_menu_row_t){"Wi-Fi setup", NULL, false};
+    rows[ROW_POWER] = (ui_menu_row_t){"Power off", "knob wakes", false};
     rows[ROW_IP] = (ui_menu_row_t){board->name, net_ip_str(), true};
     int mv, pct;
     bool usb;
@@ -189,6 +191,9 @@ menu_result_t menu_run(const cam_info_t *current, int *fav_slot_out)
             vTaskDelay(pdMS_TO_TICKS(800));
             esp_restart();
             break;
+        case ROW_POWER:
+            ui_menu_hide();
+            power_off();
         case ROW_CLOSE:
             goto out;
         default:
diff --git a/main/power.c b/main/power.c
new file mode 100644
index 0000000..53a2e98
--- /dev/null
+++ b/main/power.c
@@ -0,0 +1,60 @@
+#include "power.h"
+#include "board.h"
+#include "display.h"
+#include "leds.h"
+#include "ui.h"
+#include "driver/gpio.h"
+#include "driver/rtc_io.h"
+#include "esp_log.h"
+#include "esp_sleep.h"
+#include "esp_wifi.h"
+#include "freertos/FreeRTOS.h"
+#include "freertos/task.h"
+
+static const char *TAG = "power";
+
+// Arm ext1 wake on the encoder pins. The S3 has one level mode for all selected
+// pins, so pick it from the knob's resting state: pins that are high wake on
+// low; if both rest low, wake on high. A single detent toggles both pins.
+static void arm_knob_wakeup(void)
+{
+    int pins[2] = {board->enc_a, board->enc_b};
+    uint64_t high = 0, low = 0;
+    for (int i = 0; i < 2; i++) {
+        rtc_gpio_init(pins[i]);
+        rtc_gpio_set_direction(pins[i], RTC_GPIO_MODE_INPUT_ONLY);
+        rtc_gpio_pulldown_dis(pins[i]);
+        rtc_gpio_pullup_en(pins[i]);
+    }
+    vTaskDelay(pdMS_TO_TICKS(5));
+    for (int i = 0; i < 2; i++) {
+        if (rtc_gpio_get_level(pins[i])) high |= 1ULL << pins[i];
+        else low |= 1ULL << pins[i];
+    }
+    esp_sleep_pd_config(ESP_PD_DOMAIN_RTC_PERIPH, ESP_PD_OPTION_ON);   // keeps the RTC pull-ups alive
+    if (high) esp_sleep_enable_ext1_wakeup_io(high, ESP_EXT1_WAKEUP_ANY_LOW);
+    else esp_sleep_enable_ext1_wakeup_io(low, ESP_EXT1_WAKEUP_ANY_HIGH);
+    ESP_LOGI(TAG, "wake on knob: A%d=%d B%d=%d", board->enc_a, !!(high & (1ULL << board->enc_a)),
+             board->enc_b, !!(high & (1ULL << board->enc_b)));
+}
+
+void power_off(void)
+{
+    ESP_LOGI(TAG, "powering off");
+    ui_status("Off", "turn the knob to wake");
+    vTaskDelay(pdMS_TO_TICKS(700));
+    leds_set_mode(LED_OFF, 0);
+    vTaskDelay(pdMS_TO_TICKS(80));                 // let the ring task push the dark frame
+    display_off();
+    esp_wifi_stop();
+    gpio_set_level(board->pwr_en, 0);              // peripheral rail off (screen, ring, codec)
+    arm_knob_wakeup();
+    esp_deep_sleep_start();
+}
+
+void power_report_wakeup(void)
+{
+    esp_sleep_wakeup_cause_t cause = esp_sleep_get_wakeup_cause();
+    if (cause == ESP_SLEEP_WAKEUP_EXT1) ESP_LOGI(TAG, "woken by the knob");
+    else if (cause != ESP_SLEEP_WAKEUP_UNDEFINED) ESP_LOGI(TAG, "wakeup cause %d", cause);
+}
diff --git a/main/power.h b/main/power.h
new file mode 100644
index 0000000..c37499b
--- /dev/null
+++ b/main/power.h
@@ -0,0 +1,5 @@
+#pragma once
+// Cuts the peripheral rail and puts the ESP32 into deep sleep; a turn of the knob wakes it.
+void power_off(void) __attribute__((noreturn));
+// Logs how we came up (cold boot vs. knob wake).
+void power_report_wakeup(void);
diff --git a/main/settings.h b/main/settings.h
index 4baed4c..b3578c8 100644
--- a/main/settings.h
+++ b/main/settings.h
@@ -29,7 +29,7 @@ void settings_save(void);
 void settings_request_portal(void);
 bool settings_take_portal_request(void);
 
-#define FAV_SLOTS 12
+#define FAV_SLOTS 24
 const cam_info_t *fav_get(int slot);           // NULL when empty
 void fav_set(int slot, const cam_info_t *cam);
 void fav_clear(int slot);