diff --git a/docs/source/config-sectors.md b/docs/source/config-sectors.md
index cfd32458..9591ebe8 100644
--- a/docs/source/config-sectors.md
+++ b/docs/source/config-sectors.md
@@ -6,6 +6,9 @@ the following configuration options are exposed to the user.
 
 ```{note}
 Only single-period studies are currently supported when running sector studies.
+Set `renewable_weather_years: [2018]` for sector-coupled runs (`G` or `E-G`):
+residential and commercial demand profiles use 2018 weather data.
+Other weather years are rejected when the workflow loads the configuration.
 ```
 
 ## Carbon Limits
diff --git a/tests/static/test_config_schema.py b/tests/static/test_config_schema.py
index d07f5e77..9c8d36f9 100644
--- a/tests/static/test_config_schema.py
+++ b/tests/static/test_config_schema.py
@@ -129,3 +129,34 @@ def test_godeeep_requires_renewable_land_access_key(schema):
     cfg.pop("renewable_land_access")
     with pytest.raises(jsonschema.ValidationError):
         jsonschema.validate(cfg, schema)
+
+
+@pytest.mark.fast
+@pytest.mark.parametrize("sector", ["G", "E-G"])
+@pytest.mark.parametrize("weather_years", [[2019], [2018, 2019], []])
+def test_sector_weather_year_must_be_2018(sector, weather_years, schema):
+    cfg = _merged("config.default.yaml")
+    cfg["scenario"]["sector"] = sector
+    cfg["renewable_weather_years"] = weather_years
+    with pytest.raises(jsonschema.ValidationError) as exc_info:
+        jsonschema.validate(cfg, schema)
+    assert list(exc_info.value.path) == ["renewable_weather_years"]
+
+
+@pytest.mark.fast
+@pytest.mark.parametrize("sector", ["G", "E-G"])
+def test_sector_weather_year_2018_is_supported(sector, schema):
+    cfg = _merged("config.default.yaml")
+    cfg["scenario"]["sector"] = sector
+    cfg["renewable_weather_years"] = [2018]
+    jsonschema.validate(cfg, schema)
+
+
+@pytest.mark.fast
+@pytest.mark.parametrize("sector", ["", "E"])
+@pytest.mark.parametrize("weather_years", [[2019], [2018, 2019]])
+def test_electricity_weather_years_remain_supported(sector, weather_years, schema):
+    cfg = _merged("config.default.yaml")
+    cfg["scenario"]["sector"] = sector
+    cfg["renewable_weather_years"] = weather_years
+    jsonschema.validate(cfg, schema)
diff --git a/tests/static/test_dag_dryrun.py b/tests/static/test_dag_dryrun.py
index 1666a7cd..62323df3 100644
--- a/tests/static/test_dag_dryrun.py
+++ b/tests/static/test_dag_dryrun.py
@@ -75,6 +75,27 @@ def test_snakemake_dryrun_resolves(configfile, target, overrides):
     )
 
 
+@pytest.mark.fast
+@pytest.mark.parametrize("sector", ["G", "E-G"])
+def test_sector_weather_year_is_checked_at_workflow_start(tmp_path, sector):
+    configfile = tmp_path / "sector.yaml"
+    configfile.write_text(f"scenario:\n  sector: {sector}\nrenewable_weather_years: [2019]\n")
+    result = subprocess.run(
+        ["snakemake", "--list", "--configfile", str(configfile)],
+        cwd=WORKFLOW_DIR,
+        capture_output=True,
+        text=True,
+        timeout=60,
+    )
+    assert result.returncode != 0
+    output = result.stdout + result.stderr
+    assert "Error validating config file" in output
+    assert "renewable_weather_years" in output
+    assert "Sector-coupled runs require" in output
+    assert "[2018]" in output
+    assert "[2019]" in output
+
+
 def _solve_network_inputs(overrides):
     """Return the ``solve_network`` input paths snakemake resolves in a dry run."""
     cmd = [
diff --git a/workflow/schemas/config.schema.yaml b/workflow/schemas/config.schema.yaml
index 746dc40b..555a237f 100644
--- a/workflow/schemas/config.schema.yaml
+++ b/workflow/schemas/config.schema.yaml
@@ -506,6 +506,22 @@ properties:
       eia: {type: ["string", "null"]}
 
 allOf:
+# Residential and commercial sector demand profiles use 2018 weather data.
+- if:
+    properties:
+      scenario:
+        properties:
+          sector: {pattern: "(^|-)G(-|$)"}
+        required: [sector]
+    required: [scenario]
+  then:
+    properties:
+      renewable_weather_years:
+        description: >-
+          Sector-coupled runs require renewable_weather_years: [2018].
+          Residential and commercial demand profiles use 2018 weather data.
+        const: [2018]
+
 # The selected solver's options block must exist in solver_options.
 - if:
     properties: