diff --git a/backend/documents_parser/tests/fixtures/Summary_000565_case50.pdf b/backend/documents_parser/tests/fixtures/Summary_000565_case50.pdf
new file mode 100644
index 00000000..ab23b998
Binary files /dev/null and b/backend/documents_parser/tests/fixtures/Summary_000565_case50.pdf differ
diff --git a/tests/domain/sap10_calculator/worksheet/_elmhurst_worksheet_000565_case50.py b/tests/domain/sap10_calculator/worksheet/_elmhurst_worksheet_000565_case50.py
new file mode 100644
index 00000000..e051922b
--- /dev/null
+++ b/tests/domain/sap10_calculator/worksheet/_elmhurst_worksheet_000565_case50.py
@@ -0,0 +1,113 @@
+"""Mapper-driven cascade pin against the Elmhurst U985-0001-000565
+"simulated case 50" worksheet — an all-electric Economy-7 dwelling with
+MVHR + electric storage heaters + a DUAL-immersion hot-water cylinder.
+
+Like 000565 / the _rr cases, this fixture does NOT hand-build the
+EpcPropertyData: it routes the Summary PDF through
+ElmhurstSiteNotesExtractor + from_elmhurst_site_notes so the SAP-result
+pin grid exercises the WHOLE extractor + mapper + calculator pipeline.
+
+This case was hand-built (Khalim) to ground-truth the dual-immersion
+cylinder water-heating path, and it exercises two distinct off-peak
+tariff mechanics that the gas/standard-tariff fixtures don't reach:
+
+  - The Table 13 HW high-rate fraction for a whc-903 DUAL electric
+    immersion (0.1009 high / 0.8991 low) — the COST (6.4878 p/kWh) AND
+    the CO2/PE split ("Water heating - high/low rate cost", fixed in
+    `_electric_immersion_hw_high_rate_fraction`).
+  - The Table 12a Grid 2 fan fraction (0.71/0.58) for MVHR fan
+    electricity (315.64 kWh, 100% MVHR per worksheet line 230a) — billed
+    distinct from "all other uses" 0.90/0.80 (fixed by including the MVHR
+    fan in `mev_kwh_for_cost_split`).
+
+Unknown meter + dual electric immersion resolves to 7-hour off-peak via
+the §12 trigger. After both fixes the existing-dwelling rating reconciles
+to the U985 worksheet EXACTLY, including the (272) rating CO2.
+
+Cert shape: 000565 semi shell, main = electric storage heaters (SAP 402,
+manual charge control), portable electric secondary (SAP 693), water
+heating from a whc-903 dual electric immersion + 160 L foam cylinder (no
+cylinder stat), MVHR (Vent Axia, PCDB 500140), one instantaneous electric
+shower, no PV, Economy-7.
+
+Source: user-simulated PDFs at `sap worksheets/golden fixture debugging/
+simulated case 50/`. The Summary is mirrored into the tracked
+`backend/documents_parser/tests/fixtures/Summary_000565_case50.pdf` so the
+test runs without depending on the unstaged workspace.
+
+Worksheet pin targets (U985-0001-000565 block 1 — existing dwelling SAP):
+- SAP rating 39 (258); continuous 38.8426; ECF 4.4252 (257)
+- Total fuel cost £1317.0116 (255)
+- Total CO2 2397.1237 kg/year (272)
+- Space heating 14318.4904 kWh/year ((98c))
+- Main 1 fuel 12170.7169 kWh/year (211)
+- Secondary fuel 2147.7736 kWh/year (215)
+- Hot water fuel 1668.0788 kWh/year (219)
+- Lighting 435.3204 kWh/year (232)
+- Pumps/fans 315.6384 kWh/year (231)
+
+Per [[feedback-zero-error-strict]] + [[feedback-e2e-validation-
+philosophy]]: pins are abs=1e-4 against the worksheet PDF. The pin
+values live in `test_e2e_elmhurst_sap_score._FIXTURE_PINS`.
+"""
+
+from __future__ import annotations
+
+import re
+import subprocess
+from pathlib import Path
+from typing import Final
+
+from backend.documents_parser.elmhurst_extractor import ElmhurstSiteNotesExtractor
+from datatypes.epc.domain.epc_property_data import EpcPropertyData
+from datatypes.epc.domain.mapper import EpcPropertyDataMapper
+
+# parents[0]=worksheet/, [1]=sap10_calculator/, [2]=domain/, [3]=tests/,
+# [4]=repo root.
+_SUMMARY_PDF: Final[Path] = (
+    Path(__file__).resolve().parents[4]
+    / "backend" / "documents_parser" / "tests" / "fixtures"
+    / "Summary_000565_case50.pdf"
+)
+
+
+def _summary_pdf_to_textract_style_pages(pdf_path: Path) -> list[str]:
+    """Convert a Summary PDF into the per-page text format the
+    ElmhurstSiteNotesExtractor expects (label\\nvalue sequences). Mirror
+    of the helper in the other `_elmhurst_worksheet_*` fixtures.
+    """
+    info = subprocess.run(
+        ["pdfinfo", str(pdf_path)], capture_output=True, text=True, check=True,
+    ).stdout
+    m = re.search(r"Pages:\s+(\d+)", info)
+    if m is None:
+        raise RuntimeError(f"Could not parse page count from {pdf_path}")
+    page_count = int(m.group(1))
+    pages: list[str] = []
+    for i in range(1, page_count + 1):
+        layout = subprocess.run(
+            [
+                "pdftotext", "-layout", "-f", str(i), "-l", str(i),
+                str(pdf_path), "-",
+            ],
+            capture_output=True, text=True, check=True,
+        ).stdout
+        tokens: list[str] = []
+        for line in layout.splitlines():
+            if not line.strip():
+                tokens.append("")
+                continue
+            parts = [p for p in re.split(r"\s{2,}", line.strip()) if p]
+            tokens.extend(parts)
+        pages.append("\n".join(tokens))
+    return pages
+
+
+def build_epc() -> EpcPropertyData:
+    """Route the simulated case-50 Summary through extractor + mapper.
+    No hand-built EpcPropertyData — the extractor and mapper are part of
+    the test target.
+    """
+    pages = _summary_pdf_to_textract_style_pages(_SUMMARY_PDF)
+    site_notes = ElmhurstSiteNotesExtractor(pages).extract()
+    return EpcPropertyDataMapper.from_elmhurst_site_notes(site_notes)
diff --git a/tests/domain/sap10_calculator/worksheet/test_e2e_elmhurst_sap_score.py b/tests/domain/sap10_calculator/worksheet/test_e2e_elmhurst_sap_score.py
index 13b1b1bb..918329d9 100644
--- a/tests/domain/sap10_calculator/worksheet/test_e2e_elmhurst_sap_score.py
+++ b/tests/domain/sap10_calculator/worksheet/test_e2e_elmhurst_sap_score.py
@@ -48,6 +48,7 @@ from tests.domain.sap10_calculator.worksheet import (
     _elmhurst_worksheet_001431_case6 as _w001431_case6,
     _elmhurst_worksheet_001431_case7 as _w001431_case7,
     _elmhurst_worksheet_001431_case20 as _w001431_case20,
+    _elmhurst_worksheet_000565_case50 as _w000565_case50,
     _elmhurst_worksheet_000565_case52 as _w000565_case52,
 )
 from tests.domain.sap10_calculator.worksheet._elmhurst_fixtures import (
@@ -297,6 +298,22 @@ _FIXTURE_PINS: Final[dict[str, FixtureCascadePins]] = {
         lighting_kwh_per_yr=246.3083,
         pumps_fans_kwh_per_yr=0.0,
     ),
+    # Mapper-driven — Summary_000565_case50.pdf → extractor → mapper →
+    # calculator. All-electric Economy-7: storage-heater main (SAP 402) +
+    # MVHR + whc-903 DUAL electric immersion + 160 L cylinder. Exercises
+    # the Table 13 HW high/low split (cost + CO2/PE) AND the Table 12a
+    # Grid 2 MVHR fan fraction (0.71/0.58). Reconciles to the worksheet
+    # EXACTLY after both off-peak fixes (incl. the (272) rating CO2).
+    "000565_case50": FixtureCascadePins(
+        sap_score=39, sap_score_continuous=38.8426, ecf=4.4252,
+        total_fuel_cost_gbp=1317.0116, co2_kg_per_yr=2397.1237,
+        space_heating_kwh_per_yr=14318.4904,
+        main_heating_fuel_kwh_per_yr=12170.7169,
+        secondary_heating_fuel_kwh_per_yr=2147.7736,
+        hot_water_kwh_per_yr=1668.0788,
+        lighting_kwh_per_yr=435.3204,
+        pumps_fans_kwh_per_yr=315.6384,
+    ),
     # Mapper-driven — Summary_000565_case52.pdf → extractor → mapper →
     # calculator. Regular (non-combi) mains-gas boiler (SAP 102) + a
     # 160 L foam cylinder heated from the main (WHC 901), no cylinder
@@ -333,6 +350,7 @@ _FIXTURE_MODULES: Final[dict[str, ModuleType]] = {
     "001431_case6": _w001431_case6,
     "001431_case7": _w001431_case7,
     "001431_case20": _w001431_case20,
+    "000565_case50": _w000565_case50,
     "000565_case52": _w000565_case52,
 }