diff --git a/src/main/java/com/interplug/qcast/biz/estimate/EstimateService.java b/src/main/java/com/interplug/qcast/biz/estimate/EstimateService.java
index ad0de059..2eadd6fa 100644
--- a/src/main/java/com/interplug/qcast/biz/estimate/EstimateService.java
+++ b/src/main/java/com/interplug/qcast/biz/estimate/EstimateService.java
@@ -1393,7 +1393,7 @@ public class EstimateService {
       roofInfoResponse.setCircuitItemList(circuitItemList);
       roofInfoResponse.setRoofVolList(roofVolList);
 
-      // 인증용량 구하기 (지붕면마다 모듈과 PCS의 총 용량을 서로 비교해 낮은쪽 용량으로 합산)
+      // 인증용량 구하기 (지붕면마다 모듈과 각각의 PCS의 총 용량을 서로 비교해 낮은쪽 용량으로 합산)
       roofInfoResponse.setCertVolKw(estimateMapper.selectEstimateRoofCertVolKw(estimateRequest));
 
       estimateResponse.setRoofInfo(roofInfoResponse);
diff --git a/src/main/resources/mappers/estimate/estimateMapper.xml b/src/main/resources/mappers/estimate/estimateMapper.xml
index 745e9625..41a30b0e 100644
--- a/src/main/resources/mappers/estimate/estimateMapper.xml
+++ b/src/main/resources/mappers/estimate/estimateMapper.xml
@@ -363,11 +363,11 @@
         /* sqlid : com.interplug.qcast.biz.estimate.selectEstimateRoofCertVolKw */
         SELECT
               -- FORMAT(ISNULL(SUM(CASE WHEN T.MODULE_VOL_KW <![CDATA[ <= ]]> T.PC_VOL_KW THEN T.MODULE_VOL_KW ELSE T.PC_VOL_KW END), 0), '#,##0.000') AS CERT_VOL_KW
-              REPLACE(CONVERT(VARCHAR, CAST(ISNULL(SUM(
+              REPLACE(CONVERT(VARCHAR, SUM(CAST(ISNULL(
                 CASE
                 WHEN T.MODULE_VOL_KW <![CDATA[ <= ]]> T.PC_VOL_KW THEN T.MODULE_VOL_KW
                 ELSE T.PC_VOL_KW
-                END), 0) AS NUMERIC(18, 3)), 1), ',', '') AS CERT_VOL_KW
+                END, 0) AS NUMERIC(18, 3))), 1), ',', '') AS CERT_VOL_KW
         FROM
         (
             SELECT