diff --git a/src/hooks/floorPlan/estimate/useEstimateController.js b/src/hooks/floorPlan/estimate/useEstimateController.js
index 3f7120d8..264b9732 100644
--- a/src/hooks/floorPlan/estimate/useEstimateController.js
+++ b/src/hooks/floorPlan/estimate/useEstimateController.js
@@ -10,6 +10,8 @@ import { useRouter, useSearchParams } from 'next/navigation'
 import { FloorPlanContext } from '@/app/floor-plan/FloorPlanProvider'
 import { QcastContext } from '@/app/QcastProvider'
 import { useSwal } from '@/hooks/useSwal'
+import { POLYGON_TYPE } from '@/common/common'
+import { logger } from '@/util/logger'
 // Constants
 const ESTIMATE_API_ENDPOINT = '/api/estimate' // API 엔드포인트 정의
 
@@ -33,7 +35,7 @@ export const useEstimateController = (planNo, flag) => {
 
   const { getMessage } = useMessage()
 
-  const { promiseGet, post, promisePost } = useAxios(globalLocaleState)
+  const { promiseGet, post, promisePost, get } = useAxios(globalLocaleState)
 
   const [isLoading, setIsLoading] = useState(false)
   const { estimateContextState, setEstimateContextState } = useContext(FloorPlanContext)
@@ -386,6 +388,36 @@ export const useEstimateController = (planNo, flag) => {
     }
   }
 
+  // 견적 상세 저장 후 저장된 plan JSON 에서 회로 payload 를 만들어 CONN_VOL_W(접속용량) 백필을 요청한다.
+  const backfillConnVol = async (objectNo, planNo) => {
+    try {
+      const list = await get({ url: `/api/canvas-management/canvas-statuses/by-object/${objectNo}` })
+      const target = (list || []).find((it) => String(it.planNo) === String(planNo)) || (list || [])[0]
+      const raw = target?.canvasStatus?.replace(/##/g, '"').replace(/∠/g, '∠').replace(/°/g, '°')
+      const objects = raw ? JSON.parse(raw).objects || [] : []
+
+      const moduleObjs = objects.filter((o) => o.name === POLYGON_TYPE.MODULE)
+      const moduleList = moduleObjs.map((m) => ({ circuit: m.circuitNumber, specification: m.moduleInfo?.wpOut }))
+      if (moduleList.length === 0) return
+
+      // PCS 유닛 번호 = circuit 첫 숫자. distinct 개수 = 유닛 수, 오름차순 = 유닛 index
+      const unitNumbers = [...new Set(moduleObjs.map((m) => parseInt(String(m.circuitNumber ?? '').match(/\d+/)?.[0], 10)).filter((n) => n > 0))].sort(
+        (a, b) => a - b
+      )
+      // PCS 데이터는 surfaces[0] 에만 실려 있다.
+      const surface0 = objects.find((o) => o.name === POLYGON_TYPE.MODULE_SETUP_SURFACE)
+      const pcsList = (surface0?.pcses || []).filter((pcs) => pcs?.pcsItemId)
+      const circuitItemList = unitNumbers.map((unit) => ({ itemId: pcsList[unit - 1]?.pcsItemId }))
+
+      await promisePost({
+        url: `${ESTIMATE_API_ENDPOINT}/update-conn-vol`,
+        data: { objectNo, planNo, circuitItemList, roofSurfaceList: [{ moduleList }] },
+      })
+    } catch (e) {
+      logger.log('[UPDATE-CONN-VOL] 백필 호출 실패', e?.message)
+    }
+  }
+
   const realSave = async (fileList) => {
 
     setEstimateContextState({pricingFlag: false})
@@ -451,9 +483,11 @@ export const useEstimateController = (planNo, flag) => {
     //2. 상세데이터 저장
     try {
       setIsGlobalLoading(true)
-      await promisePost({ url: `${ESTIMATE_API_ENDPOINT}/save-estimate`, data: estimateData }).then((res) => {
+      await promisePost({ url: `${ESTIMATE_API_ENDPOINT}/save-estimate`, data: estimateData }).then(async (res) => {
         if (res.status === 201) {
           estimateData.newFileList = []
+          // 인증용량이 CONN_VOL_W 로 계산되므로, /detail 재조회(fetchSetting) 전에 백필을 먼저 끝낸다.
+          await backfillConnVol(estimateData.objectNo, estimateData.planNo)
           swalFire({ text: getMessage('estimate.detail.save.alertMsg'), type: 'alert' })
           fetchSetting(estimateData.objectNo, estimateData.planNo)
         }