diff --git a/homeassistant/components/sma/config_flow.py b/homeassistant/components/sma/config_flow.py
index f43c851d04a..e08b9ade9fc 100644
--- a/homeassistant/components/sma/config_flow.py
+++ b/homeassistant/components/sma/config_flow.py
@@ -184,7 +184,36 @@ class SmaConfigFlow(ConfigFlow, domain=DOMAIN):
         self._data[CONF_HOST] = discovery_info.ip
         self._data[CONF_MAC] = format_mac(self._discovery_data[CONF_MAC])
 
-        await self.async_set_unique_id(discovery_info.hostname.replace("SMA", ""))
+        _LOGGER.debug(
+            "DHCP discovery detected SMA device: %s, IP: %s, MAC: %s",
+            self._discovery_data[CONF_NAME],
+            self._discovery_data[CONF_HOST],
+            self._discovery_data[CONF_MAC],
+        )
+
+        existing_entries_with_host = [
+            entry
+            for entry in self._async_current_entries(include_ignore=False)
+            if entry.data.get(CONF_HOST) == self._data[CONF_HOST]
+            and not entry.data.get(CONF_MAC)
+        ]
+
+        # If we have an existing entry with the same host but no MAC address,
+        # we update the entry with the MAC address and reload it.
+        if existing_entries_with_host:
+            entry = existing_entries_with_host[0]
+            self.async_update_reload_and_abort(
+                entry, data_updates={CONF_MAC: self._data[CONF_MAC]}
+            )
+
+        # Finally, check if the hostname (which represents the SMA serial number) is unique
+        serial_number = discovery_info.hostname.lower()
+        # Example hostname: sma12345678-01
+        # Remove 'sma' prefix and strip everything after the dash (including the dash)
+        if serial_number.startswith("sma"):
+            serial_number = serial_number.removeprefix("sma")
+        serial_number = serial_number.split("-", 1)[0]
+        await self.async_set_unique_id(serial_number)
         self._abort_if_unique_id_configured()
 
         return await self.async_step_discovery_confirm()
diff --git a/tests/components/sma/test_config_flow.py b/tests/components/sma/test_config_flow.py
index 29779ec2773..b2e488318a5 100644
--- a/tests/components/sma/test_config_flow.py
+++ b/tests/components/sma/test_config_flow.py
@@ -11,8 +11,10 @@ import pytest
 
 from homeassistant.components.sma.const import DOMAIN
 from homeassistant.config_entries import SOURCE_DHCP, SOURCE_USER
+from homeassistant.const import CONF_MAC
 from homeassistant.core import HomeAssistant
 from homeassistant.data_entry_flow import FlowResultType
+from homeassistant.helpers.device_registry import format_mac
 from homeassistant.helpers.service_info.dhcp import DhcpServiceInfo
 
 from . import (
@@ -37,6 +39,12 @@ DHCP_DISCOVERY_DUPLICATE = DhcpServiceInfo(
     macaddress="0015bb00abcd",
 )
 
+DHCP_DISCOVERY_DUPLICATE_001 = DhcpServiceInfo(
+    ip="1.1.1.1",
+    hostname="SMA123456789-001",
+    macaddress="0015bb00abcd",
+)
+
 
 async def test_form(
     hass: HomeAssistant, mock_setup_entry: AsyncMock, mock_sma_client: AsyncMock
@@ -154,6 +162,31 @@ async def test_dhcp_already_configured(
     assert result["reason"] == "already_configured"
 
 
+async def test_dhcp_already_configured_duplicate(
+    hass: HomeAssistant, mock_config_entry: MockConfigEntry
+) -> None:
+    """Test starting a flow by DHCP when already configured and MAC is added."""
+    mock_config_entry.add_to_hass(hass)
+    await hass.config_entries.async_setup(mock_config_entry.entry_id)
+    await hass.async_block_till_done()
+
+    assert CONF_MAC not in mock_config_entry.data
+
+    result = await hass.config_entries.flow.async_init(
+        DOMAIN,
+        context={"source": SOURCE_DHCP},
+        data=DHCP_DISCOVERY_DUPLICATE_001,
+    )
+
+    assert result["type"] == FlowResultType.ABORT
+    assert result["reason"] == "already_configured"
+    await hass.async_block_till_done()
+
+    assert mock_config_entry.data.get(CONF_MAC) == format_mac(
+        DHCP_DISCOVERY_DUPLICATE_001.macaddress
+    )
+
+
 @pytest.mark.parametrize(
     ("exception", "error"),
     [