diff --git a/api/ecobee.php b/api/ecobee.php
index ddce844..b597f7f 100644
--- a/api/ecobee.php
+++ b/api/ecobee.php
@@ -62,12 +62,11 @@ class ecobee extends external_api {
         $ecobee_token
       );
 
-      $guids = [];
+      $identifiers = [];
       $email_addresses = [];
       foreach($response['thermostatList'] as $thermostat) {
         $runtime = $thermostat['runtime'];
-        $guid = sha1($thermostat['identifier'] . $runtime['firstConnected']);
-        $guids[] = $guid;
+        $identifiers[] = $thermostat['identifier'];
 
         $notification_settings = $thermostat['notificationSettings'];
         $email_addresses = array_merge($email_addresses, $notification_settings['emailAddresses']);
@@ -79,7 +78,7 @@ class ecobee extends external_api {
       $existing_ecobee_thermostats = $this->database->read(
         'ecobee_thermostat',
         [
-          'guid' => $guids
+          'identifier' => $identifiers
         ]
       );
 
diff --git a/api/ecobee_sensor.php b/api/ecobee_sensor.php
index 78c5fe5..5b949b3 100644
--- a/api/ecobee_sensor.php
+++ b/api/ecobee_sensor.php
@@ -100,14 +100,12 @@ class ecobee_sensor extends cora\crud {
     // Loop over the returned sensors and create/update them as necessary.
     $sensor_ids_to_keep = [];
     foreach($response['thermostatList'] as $thermostat_api) {
-      $guid = sha1($thermostat_api['identifier'] . $thermostat_api['runtime']['firstConnected']);
-
       $ecobee_thermostat = $this->api(
         'ecobee_thermostat',
         'get',
         [
           'attributes' => [
-            'guid' => $guid
+            'identifier' => $thermostat_api['identifier']
           ]
         ]
       );
diff --git a/api/ecobee_thermostat.php b/api/ecobee_thermostat.php
index d191bf0..d58b4fb 100644
--- a/api/ecobee_thermostat.php
+++ b/api/ecobee_thermostat.php
@@ -100,11 +100,9 @@ class ecobee_thermostat extends cora\crud {
     // Loop over the returned thermostats and create/update them as necessary.
     $thermostat_ids_to_keep = [];
     foreach($response['thermostatList'] as $api_thermostat) {
-      $guid = sha1($api_thermostat['identifier'] . $api_thermostat['runtime']['firstConnected']);
-
       $ecobee_thermostat = $this->get(
         [
-          'guid' => $guid
+          'identifier' => $api_thermostat['identifier']
         ]
       );
 
@@ -123,7 +121,7 @@ class ecobee_thermostat extends cora\crud {
       else {
         // Thermostat does not exist.
         $ecobee_thermostat = $this->create([
-          'guid' => $guid
+          'identifier' => $api_thermostat['identifier']
         ]);
         $thermostat = $this->api(
           'thermostat',