diff --git a/main.py b/main.py
index 0825366..d4cebf5 100644
--- a/main.py
+++ b/main.py
@@ -4,6 +4,7 @@ import os
 from dotenv import load_dotenv
 import logging
 import signal
+import time
 
 load_dotenv()
 
@@ -43,8 +44,8 @@ signal.signal(signal.SIGINT, handle_shutdown)
 
 def main():
     with serial.Serial(device_name, 115200, timeout=1) as ser:
-        inverter_offline_counter = 0
         shutdown_triggered = False
+        inverter_online = True
         while running:
             line = ser.readline().decode(errors="ignore").strip()
             if line == "":
@@ -52,13 +53,16 @@ def main():
                 continue
             elif line == "0":
                 logger.debug("Inverter Online")
-                inverter_offline_counter = 0
-            elif inverter_offline_counter >= shutdown_timer:
-                shutdown_triggered = True
-                break
+                inverter_online = True
+            elif not inverter_online:
+                if time.time() - last_online > shutdown_timer:
+                    shutdown_triggered = True
+                    break
             else:
-                inverter_offline_counter += 1
-                logger.info(f"Running on UPS reserve, offline for {inverter_offline_counter}s")
+                if inverter_online:
+                    inverter_online = False
+                    last_online = time.time()
+                    logger.info(f"Running on UPS reserve, offline for {time.time()-last_online}s")
 
         if shutdown_triggered:
             logger.info(f"Inverter offline for {shutdown_timer} seconds")