diff --git a/src/app/globals.css b/src/app/globals.css
index de46d37..d14431b 100644
--- a/src/app/globals.css
+++ b/src/app/globals.css
@@ -1541,6 +1541,16 @@ a.kpi:hover {
   color: var(--text-faint);
 }
 
+.tree-grid .downstream-board-load-row td {
+  background: var(--panel-bg-subtle);
+  color: var(--text-muted);
+  font-style: italic;
+}
+
+.tree-grid .downstream-board-load-row td:nth-child(2) {
+  padding-left: 1.5rem;
+}
+
 .tree-grid .empty-circuit-row td {
   background: var(--panel-bg-subtle);
 }
diff --git a/src/app/projects/[projectId]/page.tsx b/src/app/projects/[projectId]/page.tsx
index ed03cd9..4a99cf0 100644
--- a/src/app/projects/[projectId]/page.tsx
+++ b/src/app/projects/[projectId]/page.tsx
@@ -56,6 +56,7 @@ import {
   disconnectProjectDeviceRows,
   exportProjectTransfer,
   getProject,
+  getProjectCircuitTrees,
   getProjectDeviceSyncPreview,
   listBuildings,
   listCircuitLists,
@@ -73,6 +74,7 @@ import {
 import type {
   BuildingDto,
   CircuitListDto,
+  CircuitTreeResponseDto,
   CreateRoomInput,
   CreateProjectDeviceInput,
   DistributionBoardDto,
@@ -151,6 +153,7 @@ export default function ProjectDetailPage() {
   const [project, setProject] = useState<ProjectDto | null>(null);
   const [boards, setBoards] = useState<DistributionBoardDto[]>([]);
   const [circuitLists, setCircuitLists] = useState<CircuitListDto[]>([]);
+  const [circuitTrees, setCircuitTrees] = useState<CircuitTreeResponseDto[]>([]);
   const [buildings, setBuildings] = useState<BuildingDto[]>([]);
   const [floors, setFloors] = useState<FloorDto[]>([]);
   const [rooms, setRooms] = useState<RoomDto[]>([]);
@@ -170,6 +173,8 @@ export default function ProjectDetailPage() {
     setEditingBoardSimultaneityFactor,
   ] = useState("1");
   const [editingBoardCopyName, setEditingBoardCopyName] = useState("");
+  const [editingFeedingBoardId, setEditingFeedingBoardId] = useState("");
+  const [editingFeedingCircuitId, setEditingFeedingCircuitId] = useState("");
   const [editingBoardInfo, setEditingBoardInfo] =
     useState<DistributionBoardInfoDraft>(
       toDistributionBoardInfoDraft({
@@ -209,6 +214,7 @@ export default function ProjectDetailPage() {
       getProject(projectId),
       listDistributionBoards(projectId),
       listCircuitLists(projectId),
+      getProjectCircuitTrees(projectId),
       listBuildings(projectId),
       listFloors(projectId),
       listRooms(projectId),
@@ -219,6 +225,7 @@ export default function ProjectDetailPage() {
         currentProject,
         distributionBoards,
         loadedCircuitLists,
+        loadedCircuitTrees,
         loadedBuildings,
         loadedFloors,
         loadedRooms,
@@ -228,6 +235,7 @@ export default function ProjectDetailPage() {
         setProject(currentProject);
         setBoards(distributionBoards);
         setCircuitLists(loadedCircuitLists);
+        setCircuitTrees(loadedCircuitTrees.trees);
         setBuildings(loadedBuildings);
         setFloors(loadedFloors);
         setRooms(loadedRooms);
@@ -310,6 +318,48 @@ export default function ProjectDetailPage() {
     () => new Map(circuitLists.map((circuitList) => [circuitList.distributionBoardId, circuitList])),
     [circuitLists]
   );
+  const circuitTreeByBoardId = useMemo(
+    () => new Map(circuitTrees.map((tree) => [tree.distributionBoardId, tree])),
+    [circuitTrees]
+  );
+  const feedingBoardOptions = useMemo(() => {
+    if (!editingBoard) return [];
+    const boardById = new Map(boards.map((board) => [board.id, board]));
+    return boards.filter((candidate) => {
+      if (candidate.id === editingBoard.id) return false;
+      const visited = new Set<string>();
+      let current: DistributionBoardDto | undefined = candidate;
+      while (current && current.feedingDistributionBoardId && !visited.has(current.id)) {
+        if (current.feedingDistributionBoardId === editingBoard.id) return false;
+        visited.add(current.id);
+        current = boardById.get(current.feedingDistributionBoardId);
+      }
+      return true;
+    });
+  }, [boards, editingBoard]);
+  const selectedFeedingTree = editingFeedingBoardId
+    ? circuitTreeByBoardId.get(editingFeedingBoardId)
+    : undefined;
+  const selectedFeedingCircuits = useMemo(
+    () =>
+      selectedFeedingTree?.sections.flatMap((section) =>
+        section.circuits.map((circuit) => ({ circuit, section }))
+      ) ?? [],
+    [selectedFeedingTree]
+  );
+  const selectedFeedingCircuit = selectedFeedingCircuits.find(
+    ({ circuit }) => circuit.id === editingFeedingCircuitId
+  );
+  const selectedFeedingBoard = boards.find(
+    (board) => board.id === editingFeedingBoardId
+  );
+  const selectedFeedingCircuitUseCount = editingFeedingCircuitId
+    ? boards.filter(
+        (board) =>
+          board.id !== editingBoard?.id &&
+          board.feedingCircuitId === editingFeedingCircuitId
+      ).length
+    : 0;
   const enabledBoardSupplyTypes =
     project?.enabledDistributionBoardSupplyTypes ?? [];
   const usedBoardSupplyTypes = useMemo(
@@ -329,6 +379,21 @@ export default function ProjectDetailPage() {
     [boards]
   );
 
+  function formatBoardFeedingReference(board: DistributionBoardDto) {
+    if (!board.feedingDistributionBoardId) return board.fedFrom ?? "–";
+    const feedingBoard = boards.find(
+      (candidate) => candidate.id === board.feedingDistributionBoardId
+    );
+    if (!feedingBoard) return "Unbekannte Verteilung";
+    const boardLabel = feedingBoard.boardNumber ?? feedingBoard.name;
+    if (!board.feedingCircuitId) return boardLabel;
+    const circuit = circuitTreeByBoardId
+      .get(feedingBoard.id)
+      ?.sections.flatMap((section) => section.circuits)
+      .find((candidate) => candidate.id === board.feedingCircuitId);
+    return `${boardLabel}${circuit?.equipmentIdentifier ?? ""}`;
+  }
+
   function applyProjectRevision(currentRevision: number) {
     setProject((current) =>
       current ? { ...current, currentRevision } : current
@@ -358,6 +423,7 @@ export default function ProjectDetailPage() {
       ]);
       setCircuitLists(await listCircuitLists(projectId));
       applyProjectRevision(result.history.currentRevision);
+      setCircuitTrees((await getProjectCircuitTrees(projectId)).trees);
       setBoardName("");
       setBoardFloorId("");
       setBoardSupplyType(
@@ -488,6 +554,8 @@ export default function ProjectDetailPage() {
     );
     setEditingBoardCopyName(`${board.name} Kopie`);
     setEditingBoardInfo(toDistributionBoardInfoDraft(board));
+    setEditingFeedingBoardId(board.feedingDistributionBoardId ?? "");
+    setEditingFeedingCircuitId(board.feedingCircuitId ?? "");
   }
 
   function openBoardCreator() {
@@ -523,6 +591,8 @@ export default function ProjectDetailPage() {
           floorId: editingBoardFloorId || null,
           supplyType: editingBoardSupplyType,
           simultaneityFactor,
+          feedingDistributionBoardId: editingFeedingBoardId || null,
+          feedingCircuitId: editingFeedingCircuitId || null,
           ...fromDistributionBoardInfoDraft(editingBoardInfo),
         },
         project.currentRevision
@@ -535,6 +605,7 @@ export default function ProjectDetailPage() {
         )
       );
       applyProjectRevision(result.history.currentRevision);
+      setCircuitTrees((await getProjectCircuitTrees(projectId)).trees);
       setEditingBoard(null);
     } catch (err) {
       setError(
@@ -590,6 +661,7 @@ export default function ProjectDetailPage() {
         result.circuitList,
       ]);
       applyProjectRevision(result.history.currentRevision);
+      setCircuitTrees((await getProjectCircuitTrees(projectId)).trees);
       setEditingBoard(null);
     } catch (err) {
       setError(
@@ -633,6 +705,7 @@ export default function ProjectDetailPage() {
         )
       );
       applyProjectRevision(result.history.currentRevision);
+      setCircuitTrees((await getProjectCircuitTrees(projectId)).trees);
       setEditingBoard(null);
     } catch (err) {
       setError(
@@ -989,6 +1062,7 @@ export default function ProjectDetailPage() {
                     <th>Örtlichkeit</th>
                     <th>Etage</th>
                     <th>Netzart</th>
+                    <th>Gespeist von</th>
                     <th>GZF</th>
                     <th className="text-end">Aktionen</th>
                   </tr>
@@ -1015,6 +1089,7 @@ export default function ProjectDetailPage() {
                               ]
                             : "Nicht festgelegt"}
                         </td>
+                        <td>{formatBoardFeedingReference(board)}</td>
                         <td>
                           {board.simultaneityFactor.toLocaleString(
                             "de-DE",
@@ -1392,7 +1467,7 @@ export default function ProjectDetailPage() {
 
       {editingBoard ? (
         <FormModal
-          description={`${editingBoard.name}: Etagenzuordnung, Netzart und Gleichzeitigkeitsfaktor ändern.`}
+          description={`${editingBoard.name}: Etagenzuordnung, Netzart, Einspeisung und Gleichzeitigkeitsfaktor ändern.`}
           isSaving={isSaving}
           onClose={() => setEditingBoard(null)}
           onSubmit={handleUpdateBoard}
@@ -1479,6 +1554,91 @@ export default function ProjectDetailPage() {
               </div>
             </div>
           </div>
+          <section className="card mt-4" aria-labelledby="feeding-reference-heading">
+            <div className="card-header" id="feeding-reference-heading">
+              Logische Einspeisung
+            </div>
+            <div className="card-body row g-3">
+              <div className="col-12 col-md-6">
+                <label className="form-label" htmlFor="feeding-distribution-board">
+                  Speisende Verteilung
+                </label>
+                <select
+                  className="form-select"
+                  id="feeding-distribution-board"
+                  onChange={(event) => {
+                    setEditingFeedingBoardId(event.target.value);
+                    setEditingFeedingCircuitId("");
+                  }}
+                  value={editingFeedingBoardId}
+                >
+                  <option value="">Keine Projektverteilung</option>
+                  {feedingBoardOptions.map((board) => (
+                    <option key={board.id} value={board.id}>
+                      {board.boardNumber ?? board.name}
+                    </option>
+                  ))}
+                </select>
+              </div>
+              <div className="col-12 col-md-6">
+                <label className="form-label" htmlFor="feeding-circuit">
+                  Speisender Abgang
+                </label>
+                <select
+                  className="form-select"
+                  disabled={!editingFeedingBoardId}
+                  id="feeding-circuit"
+                  onChange={(event) => setEditingFeedingCircuitId(event.target.value)}
+                  value={editingFeedingCircuitId}
+                >
+                  <option value="">Nur Verteilung bekannt</option>
+                  {selectedFeedingCircuits.map(({ circuit }) => (
+                    <option key={circuit.id} value={circuit.id}>
+                      {circuit.equipmentIdentifier}
+                      {circuit.displayName ? ` · ${circuit.displayName}` : ""}
+                    </option>
+                  ))}
+                </select>
+              </div>
+              {editingFeedingBoardId && !editingFeedingCircuitId ? (
+                <div className="col-12">
+                  <div className="alert alert-warning mb-0 py-2">
+                    Ohne speisenden Abgang wird die Hierarchie angezeigt, die
+                    Leistung dieser Verteilung aber keinem Stromkreis zugerechnet.
+                  </div>
+                </div>
+              ) : null}
+              {selectedFeedingBoard?.supplyType &&
+              editingBoardSupplyType !== selectedFeedingBoard.supplyType ? (
+                <div className="col-12">
+                  <div className="alert alert-warning mb-0 py-2">
+                    Die Netzarten weichen ab: {selectedFeedingBoard.supplyType}
+                    {" → "}{editingBoardSupplyType}. Bitte Umschaltung und
+                    Versorgungskonzept prüfen.
+                  </div>
+                </div>
+              ) : null}
+              {selectedFeedingCircuit &&
+              selectedFeedingCircuit.section.category !== "three_phase" ? (
+                <div className="col-12">
+                  <div className="alert alert-warning mb-0 py-2">
+                    Der gewählte Abgang ist 1-phasig. Bitte prüfen, ob diese
+                    Einspeisung für die Unterverteilung geeignet ist.
+                  </div>
+                </div>
+              ) : null}
+              {selectedFeedingCircuitUseCount > 0 ? (
+                <div className="col-12">
+                  <div className="alert alert-info mb-0 py-2">
+                    Dieser Abgang speist bereits {selectedFeedingCircuitUseCount}
+                    {selectedFeedingCircuitUseCount === 1
+                      ? " weitere Verteilung."
+                      : " weitere Verteilungen."}
+                  </div>
+                </div>
+              ) : null}
+            </div>
+          </section>
           <div className="mt-4">
             <DistributionBoardInfoCard
               draft={editingBoardInfo}
diff --git a/src/domain/models/circuit-tree.model.ts b/src/domain/models/circuit-tree.model.ts
index 2e1aa72..00a0c2d 100644
--- a/src/domain/models/circuit-tree.model.ts
+++ b/src/domain/models/circuit-tree.model.ts
@@ -90,6 +90,7 @@ export interface CircuitTreeDownstreamBoardLoad {
 
 export interface CircuitTreeFeedingReference {
   distributionBoardId: string;
+  circuitListId: string;
   distributionBoardName: string;
   distributionBoardNumber?: string;
   circuitId?: string;
diff --git a/src/frontend/components/cable-sizing-defaults.ts b/src/frontend/components/cable-sizing-defaults.ts
index ae4c7a4..069c575 100644
--- a/src/frontend/components/cable-sizing-defaults.ts
+++ b/src/frontend/components/cable-sizing-defaults.ts
@@ -22,6 +22,9 @@ export function deriveCircuitPhase(
  * Rows without cos φ count as 1; a circuit without load yields 1.
  */
 export function deriveCircuitCosPhi(circuit: CircuitTreeCircuitDto): number {
+  if (Number.isFinite(circuit.circuitCosPhi) && circuit.circuitCosPhi > 0) {
+    return Math.round(circuit.circuitCosPhi * 100) / 100;
+  }
   let activePowerKw = 0;
   let apparentPowerKva = 0;
   for (const row of circuit.deviceRows) {
diff --git a/src/frontend/components/circuit-tree-editor.tsx b/src/frontend/components/circuit-tree-editor.tsx
index e8a2f23..bac08ce 100644
--- a/src/frontend/components/circuit-tree-editor.tsx
+++ b/src/frontend/components/circuit-tree-editor.tsx
@@ -1,5 +1,6 @@
 "use client";
 
+import Link from "next/link";
 import { DragEvent, KeyboardEvent, useEffect, useMemo, useRef, useState } from "react";
 import {
   ArrowDown,
@@ -3293,6 +3294,23 @@ export function CircuitTreeEditor(props: { projectId: string; circuitListId: str
           threePhaseVoltageV={data.threePhaseVoltageV}
         />
       ) : null}
+      {data.feedingReference ? (
+        <div className="alert alert-info py-2" role="status">
+          Gespeist von{" "}
+          <Link
+            href={`/projects/${projectId}/circuit-lists/${
+              data.feedingReference.circuitListId
+            }/tree-edit`}
+          >
+            {data.feedingReference.distributionBoardNumber ??
+              data.feedingReference.distributionBoardName}
+            {data.feedingReference.circuitEquipmentIdentifier ?? ""}
+          </Link>
+          {data.feedingReference.circuitId
+            ? null
+            : " (speisender Stromkreis noch nicht festgelegt)"}
+        </div>
+      ) : null}
       <div className="editor-toolbar">
         <IconButton
           disabled={!historyState || historyState.undoDepth === 0 || historyBusy || isSaving}
@@ -4062,6 +4080,8 @@ export function CircuitTreeEditor(props: { projectId: string; circuitListId: str
                       ? "summary-row"
                       : row.rowType === "deviceRow"
                         ? "device-row"
+                        : row.rowType === "downstreamBoardLoad"
+                          ? "downstream-board-load-row"
                         : row.rowType === "reserveCircuit"
                           ? "empty-circuit-row"
                           : row.rowType === "placeholder"
@@ -4667,7 +4687,10 @@ export function CircuitTreeEditor(props: { projectId: string; circuitListId: str
                         : ""
                     }`}
                   >
-                    {row.circuit && row.rowType !== "deviceRow" ? (
+                    {row.circuit &&
+                    (row.rowType === "circuitCompact" ||
+                      row.rowType === "circuitSummary" ||
+                      row.rowType === "reserveCircuit") ? (
                       <>
                         <IconButton
                           disabled={isSaving}
diff --git a/src/frontend/components/distribution-board-info-card.tsx b/src/frontend/components/distribution-board-info-card.tsx
index f2523f4..dcc4188 100644
--- a/src/frontend/components/distribution-board-info-card.tsx
+++ b/src/frontend/components/distribution-board-info-card.tsx
@@ -13,7 +13,7 @@ export type DistributionBoardInfoDraft = Record<DistributionBoardInfoField, stri
 const placeholders: Record<DistributionBoardInfoField, string> = {
   boardNumber: "z. B. UV 1.1",
   location: "z. B. Raum 003 Technik",
-  fedFrom: "z. B. HV 0.1 oder HAK / Zähleranlage",
+  fedFrom: "z. B. HAK, Zähleranlage, Trafo oder NEA",
   remark: "",
 };
 
@@ -98,8 +98,8 @@ export function DistributionBoardInfoCard({
             )}
             {field === "fedFrom" ? (
               <div className="form-text">
-                Vorerst Freitext. Die logische Verknüpfung mit dem
-                speisenden Verteiler folgt.
+                Für externe Einspeisungen oder ergänzende Hinweise. Eine
+                speisende Projektverteilung wird oben logisch verknüpft.
               </div>
             ) : null}
           </div>
diff --git a/src/frontend/types.ts b/src/frontend/types.ts
index 8a2dec4..572182b 100644
--- a/src/frontend/types.ts
+++ b/src/frontend/types.ts
@@ -494,6 +494,7 @@ export interface CircuitTreeDownstreamBoardLoadDto {
 
 export interface CircuitTreeFeedingReferenceDto {
   distributionBoardId: string;
+  circuitListId: string;
   distributionBoardName: string;
   distributionBoardNumber?: string;
   circuitId?: string;
diff --git a/src/frontend/utils/circuit-grid-model.ts b/src/frontend/utils/circuit-grid-model.ts
index ba4be98..faa4a11 100644
--- a/src/frontend/utils/circuit-grid-model.ts
+++ b/src/frontend/utils/circuit-grid-model.ts
@@ -44,6 +44,7 @@ export type RowType =
   | "circuitCompact"
   | "circuitSummary"
   | "deviceRow"
+  | "downstreamBoardLoad"
   | "reserveCircuit"
   | "placeholder"
   | "footerComponent";
@@ -614,6 +615,7 @@ export function getCellKind(rowType: RowType, key: CellKey): CellKind {
     return "readonly";
   }
   if (rowType === "deviceRow") return deviceFieldKeys.has(key) ? "deviceField" : "readonly";
+  if (rowType === "downstreamBoardLoad") return "readonly";
   if (rowType === "circuitSummary") return circuitFieldKeys.has(key) ? "circuitField" : "readonly";
   if (rowType === "reserveCircuit" || rowType === "circuitCompact") {
     if (deviceFieldKeys.has(key)) return "deviceField";
diff --git a/src/frontend/utils/circuit-grid-projection.ts b/src/frontend/utils/circuit-grid-projection.ts
index fb2a846..a9b11de 100644
--- a/src/frontend/utils/circuit-grid-projection.ts
+++ b/src/frontend/utils/circuit-grid-projection.ts
@@ -2,6 +2,7 @@ import type {
   CircuitTreeCircuitDto,
   CircuitTreeComponentDto,
   CircuitTreeDeviceRowDto,
+  CircuitTreeDownstreamBoardLoadDto,
   CircuitTreeSectionDto,
 } from "../types.js";
 import { buildCircuitStructureProjection } from "./circuit-structure-projection";
@@ -45,6 +46,7 @@ export interface VisibleGridRow {
   circuit?: CircuitTreeCircuitDto;
   device?: CircuitTreeDeviceRowDto;
   component?: CircuitTreeComponentDto;
+  downstreamBoardLoad?: CircuitTreeDownstreamBoardLoadDto;
   cells: VisibleGridCell[];
 }
 
@@ -126,13 +128,16 @@ function makeVisibleGridRow(
   rowType: RowType,
   sectionId: string,
   circuit?: CircuitTreeCircuitDto,
-  device?: CircuitTreeDeviceRowDto
+  device?: CircuitTreeDeviceRowDto,
+  downstreamBoardLoad?: CircuitTreeDownstreamBoardLoadDto
 ): VisibleGridRow {
   const rowKey =
     rowType === "placeholder"
       ? `placeholder:${sectionId}`
       : rowType === "deviceRow" && device
         ? `device:${device.id}`
+        : rowType === "downstreamBoardLoad" && downstreamBoardLoad
+          ? `downstream-board:${circuit?.id}:${downstreamBoardLoad.distributionBoardId}`
         : `${rowType}:${circuit?.id ?? sectionId}`;
 
   const cells = allColumns.map((column): VisibleGridCell => {
@@ -140,7 +145,17 @@ function makeVisibleGridRow(
     const editable = kind === "circuitField" || kind === "deviceField";
     let value: GridValue;
 
-    if (rowType === "placeholder") {
+    if (rowType === "downstreamBoardLoad" && downstreamBoardLoad) {
+      value = column.key === "displayName"
+        ? `Unterverteilung ${downstreamBoardLoad.boardNumber ?? downstreamBoardLoad.name}`
+        : column.key === "rowTotalPower"
+          ? downstreamBoardLoad.activePowerKw
+          : column.key === "cosPhi"
+            ? downstreamBoardLoad.cosPhi
+            : column.key === "remark"
+              ? "Automatisch aus der verknüpften Verteilung"
+              : undefined;
+    } else if (rowType === "placeholder") {
       value = column.key === "equipmentIdentifier" ? "-frei-" : undefined;
     } else if (kind === "deviceField" && device) {
       value = getDeviceValue(device, column.key);
@@ -166,7 +181,15 @@ function makeVisibleGridRow(
     return { cellKey: column.key, editable, kind, value };
   });
 
-  return { rowKey, rowType, sectionId, circuit, device, cells };
+  return {
+    rowKey,
+    rowType,
+    sectionId,
+    circuit,
+    device,
+    downstreamBoardLoad,
+    cells,
+  };
 }
 
 export function buildVisibleGridRowsWithStructure(
@@ -221,15 +244,27 @@ export function buildVisibleGridRowsWithStructure(
     }
     if (row.rowType === "circuitBlock") {
       const circuit = row.circuit;
-      if (circuit.deviceRows.length === 0) {
+      const downstreamLoads = circuit.downstreamBoardLoads ?? [];
+      if (circuit.deviceRows.length === 0 && downstreamLoads.length === 0) {
         rows.push(makeVisibleGridRow("reserveCircuit", section.id, circuit));
-      } else if (circuit.deviceRows.length === 1) {
+      } else if (circuit.deviceRows.length === 1 && downstreamLoads.length === 0) {
         rows.push(makeVisibleGridRow("circuitCompact", section.id, circuit, circuit.deviceRows[0]));
       } else {
         rows.push(makeVisibleGridRow("circuitSummary", section.id, circuit));
         for (const device of circuit.deviceRows) {
           rows.push(makeVisibleGridRow("deviceRow", section.id, circuit, device));
         }
+        for (const load of downstreamLoads) {
+          rows.push(
+            makeVisibleGridRow(
+              "downstreamBoardLoad",
+              section.id,
+              circuit,
+              undefined,
+              load
+            )
+          );
+        }
       }
       continue;
     }
diff --git a/src/server/controllers/circuit-tree.controller.ts b/src/server/controllers/circuit-tree.controller.ts
index 22b4a73..17ac134 100644
--- a/src/server/controllers/circuit-tree.controller.ts
+++ b/src/server/controllers/circuit-tree.controller.ts
@@ -104,6 +104,9 @@ export async function buildProjectCircuitTrees(
 
   const boardById = new Map(boards.map((board) => [board.id, board]));
   const listById = new Map(lists.map((list) => [list.id, list]));
+  const listByBoardId = new Map(
+    lists.map((list) => [list.distributionBoardId, list])
+  );
   const sectionById = new Map(sections.map((section) => [section.id, section]));
   const circuitById = new Map(circuits.map((circuit) => [circuit.id, circuit]));
   const rowsByCircuitId = groupBy(rows, (row) => row.circuitId);
@@ -158,6 +161,7 @@ export async function buildProjectCircuitTrees(
       feedingReference: resolveFeedingReference(
         board,
         boardById,
+        listByBoardId,
         circuitById,
         sectionById
       ),
@@ -252,7 +256,9 @@ export async function buildProjectCircuitTrees(
         voltage: circuit.voltage ?? undefined,
         controlRequirement: circuit.controlRequirement ?? undefined,
         status: circuit.status ?? undefined,
-        isReserve: Boolean(circuit.isReserve),
+        isReserve:
+          Boolean(circuit.isReserve) &&
+          circuitLoad.downstreamBoards.length === 0,
         remark: circuit.remark ?? undefined,
         circuitTotalPower: circuitLoad.activePowerKw,
         circuitApparentPower: circuitLoad.apparentPowerKva,
@@ -292,17 +298,21 @@ export async function buildProjectCircuitTrees(
 function resolveFeedingReference(
   board: Awaited<ReturnType<typeof distributionBoardRepository.listByProject>>[number],
   boardById: Map<string, Awaited<ReturnType<typeof distributionBoardRepository.listByProject>>[number]>,
+  listByBoardId: Map<string, Awaited<ReturnType<typeof circuitListRepository.listByProject>>[number]>,
   circuitById: Map<string, Awaited<ReturnType<typeof circuitRepository.listByCircuitLists>>[number]>,
   sectionById: Map<string, Awaited<ReturnType<typeof circuitSectionRepository.listByCircuitLists>>[number]>
 ) {
   if (board.feedingDistributionBoardId === null) return undefined;
   const feedingBoard = boardById.get(board.feedingDistributionBoardId);
   if (!feedingBoard) throw new Error("Feeding distribution board is missing.");
+  const feedingList = listByBoardId.get(feedingBoard.id);
+  if (!feedingList) throw new Error("Feeding circuit list is missing.");
   const feedingCircuit = board.feedingCircuitId === null
     ? undefined
     : circuitById.get(board.feedingCircuitId);
   return {
     distributionBoardId: feedingBoard.id,
+    circuitListId: feedingList.id,
     distributionBoardName: feedingBoard.name,
     distributionBoardNumber: feedingBoard.boardNumber ?? undefined,
     circuitId: feedingCircuit?.id,
diff --git a/tests/cable-sizing-calculation.test.ts b/tests/cable-sizing-calculation.test.ts
index 39cfbb1..53d81a1 100644
--- a/tests/cable-sizing-calculation.test.ts
+++ b/tests/cable-sizing-calculation.test.ts
@@ -267,6 +267,15 @@ describe("cable sizing defaults from the circuit", () => {
     sortOrder: 1,
     isReserve: rows.length === 0,
     circuitTotalPower: rows.reduce((sum, row) => sum + row.power, 0),
+    circuitApparentPower: rows.reduce(
+      (sum, row) => sum + row.power / (row.cosPhi ?? 1),
+      0
+    ),
+    circuitCosPhi: rows.length
+      ? rows.reduce((sum, row) => sum + row.power, 0) /
+        rows.reduce((sum, row) => sum + row.power / (row.cosPhi ?? 1), 0)
+      : 1,
+    downstreamBoardLoads: [],
     deviceRows: rows.map((row, index) => ({
       id: `row-${index}`,
       sortOrder: index,
@@ -288,6 +297,19 @@ describe("cable sizing defaults from the circuit", () => {
     assert.equal(deriveCircuitCosPhi(circuit([])), 1);
   });
 
+  it("uses the projected cos φ including downstream boards", () => {
+    const feeder = circuit([{ power: 1, cosPhi: 1 }]);
+    feeder.circuitCosPhi = 0.67;
+    feeder.downstreamBoardLoads = [{
+      distributionBoardId: "uv-2",
+      name: "UV 2",
+      activePowerKw: 3,
+      apparentPowerKva: 5,
+      cosPhi: 0.6,
+    }];
+    assert.equal(deriveCircuitCosPhi(feeder), 0.67);
+  });
+
   it("derives the phase from the group category or three-phase rows", () => {
     assert.equal(deriveCircuitPhase(circuit([{ power: 1, phaseType: "single_phase" }]), "single_phase"), 1);
     assert.equal(deriveCircuitPhase(circuit([{ power: 1, phaseType: "three_phase" }]), "single_phase"), 3);
diff --git a/tests/circuit-grid-projection.test.ts b/tests/circuit-grid-projection.test.ts
index 952e3d6..1a16913 100644
--- a/tests/circuit-grid-projection.test.ts
+++ b/tests/circuit-grid-projection.test.ts
@@ -47,7 +47,10 @@ function makeCircuit(
     sortOrder,
     isReserve: deviceRows.length === 0,
     circuitTotalPower: deviceRows.reduce((total, row) => total + row.rowTotalPower, 0),
+    circuitApparentPower: deviceRows.reduce((total, row) => total + row.rowTotalPower, 0),
+    circuitCosPhi: 1,
     deviceRows,
+    downstreamBoardLoads: [],
   };
 }
 
@@ -176,6 +179,44 @@ describe("circuit grid projection", () => {
     );
   });
 
+  it("renders linked downstream boards as separate read-only rows", () => {
+    const feeder = {
+      ...reserveCircuit,
+      isReserve: false,
+      circuitTotalPower: 4,
+      circuitApparentPower: 5,
+      circuitCosPhi: 0.8,
+      downstreamBoardLoads: [{
+        distributionBoardId: "board-child",
+        name: "Unterverteilung",
+        boardNumber: "UV-02",
+        activePowerKw: 4,
+        apparentPowerKva: 5,
+        cosPhi: 0.8,
+      }],
+    };
+    const rows = buildVisibleGridRowsWithStructure(
+      [{ ...sections[0], circuits: [feeder] }],
+      { headerComponents: [], footerComponents: [] }
+    );
+    assert.deepEqual(rows.map((row) => row.rowType), [
+      "section",
+      "circuitSummary",
+      "downstreamBoardLoad",
+      "placeholder",
+    ]);
+    const loadRow = rows[2];
+    assert.equal(
+      loadRow.cells.find((cell) => cell.cellKey === "displayName")?.value,
+      "Unterverteilung UV-02"
+    );
+    assert.equal(
+      loadRow.cells.find((cell) => cell.cellKey === "rowTotalPower")?.value,
+      4
+    );
+    assert.equal(loadRow.cells.every((cell) => !cell.editable), true);
+  });
+
   it("shows circuit protection once on each visible circuit row", () => {
     const protectedSections = sections.map((section) => ({
       ...section,