diff --git a/changelog.md b/changelog.md
index 2620487..fc71bad 100644
--- a/changelog.md
+++ b/changelog.md
@@ -1,7 +1,9 @@
 # EAS Python client
 ## [0.28.0] - UNRELEASED
 ### Breaking Changes
-* None.
+* For `CandidateGenerationConfig`, replaced `voltage_delta_avg_threshold` with `average_voltage_spread_threshold`, which serves the same purpose but is
+  in volts instead of voltage per-unit.
+  * EAS must support this change in the GraphQL schema (`v2.10.0` and above).
 
 ### New Features
 * None.
diff --git a/src/zepben/eas/client/eas_client.py b/src/zepben/eas/client/eas_client.py
index 5c93fe1..0709c8b 100644
--- a/src/zepben/eas/client/eas_client.py
+++ b/src/zepben/eas/client/eas_client.py
@@ -386,11 +386,11 @@ def work_package_config_to_json(self, work_package: WorkPackageConfig) -> dict:
                     "candidateGeneration": work_package.intervention.candidate_generation and {
                         "type": work_package.intervention.candidate_generation.type.name,
                         "interventionCriteriaName": work_package.intervention.candidate_generation.intervention_criteria_name,
-                        "voltageDeltaAvgThreshold": work_package.intervention.candidate_generation.voltage_delta_avg_threshold,
+                        "averageVoltageSpreadThreshold": work_package.intervention.candidate_generation.average_voltage_spread_threshold,
                         "voltageUnderLimitHoursThreshold": work_package.intervention.candidate_generation.voltage_under_limit_hours_threshold,
                         "voltageOverLimitHoursThreshold": work_package.intervention.candidate_generation.voltage_over_limit_hours_threshold,
                         "tapWeightingFactorLowerThreshold": work_package.intervention.candidate_generation.tap_weighting_factor_lower_threshold,
-                        "tapWeightingFactorUpperThreshold": work_package.intervention.candidate_generation.tap_weighting_factor_upper_threshold,
+                        "tapWeightingFactorUpperThreshold": work_package.intervention.candidate_generation.tap_weighting_factor_upper_threshold
                     },
                     "allocationCriteria": work_package.intervention.allocation_criteria,
                     "specificAllocationInstance": work_package.intervention.specific_allocation_instance,
diff --git a/src/zepben/eas/client/work_package.py b/src/zepben/eas/client/work_package.py
index caa60e9..6343933 100644
--- a/src/zepben/eas/client/work_package.py
+++ b/src/zepben/eas/client/work_package.py
@@ -767,9 +767,13 @@ class CandidateGenerationConfig:
     base work package run. Only used when type is CRITERIA.
     """
 
-    voltage_delta_avg_threshold: Optional[float] = None
+    average_voltage_spread_threshold: Optional[int] = None
     """
-    The threshold for average deviation in voltage p.u. across the transformer. Only used when type is TAP_OPTIMIZATION.
+    The threshold for average line voltage spread under the transformer over the year, in volts.
+    Voltage spread at each timestep is calculated by taking the difference between the maximum and minimum phase-to-phase voltage over
+    the nodes under the transformer, for each phase, then taking the maximum of that difference across all phases.
+    When the average voltage spread exceeds this threshold, it indicates that the transformer is experiencing a
+    significant voltage swing that may impact system stability. Only used when type is TAP_OPTIMIZATION.
     """
 
     voltage_under_limit_hours_threshold: Optional[int] = None
diff --git a/test/test_eas_client.py b/test/test_eas_client.py
index e8b68a3..f2504e2 100644
--- a/test/test_eas_client.py
+++ b/test/test_eas_client.py
@@ -17,7 +17,7 @@
 from werkzeug import Response
 from zepben.ewb.auth import ZepbenTokenFetcher
 
-from zepben.eas import EasClient, Study, SolveConfig, InterventionConfig, YearRange
+from zepben.eas import EasClient, Study, SolveConfig, InterventionConfig, YearRange, CandidateGenerationConfig, CandidateGenerationType
 from zepben.eas import FeederConfig, ForecastConfig, FixedTimeLoadOverride
 from zepben.eas.client.ingestor import IngestorConfigInput, IngestorRunsSortCriteriaInput, IngestorRunsFilterInput, \
     IngestorRunState, IngestorRuntimeKind
@@ -1744,3 +1744,53 @@ def test_work_package_config_to_json_includes_server_defaulted_fields_if_specifi
         "dvms": None,
         "allocationLimitPerYear": 5
     }
+
+def test_work_package_config_to_json_for_tap_optimization(httpserver: HTTPServer):
+    eas_client = EasClient(
+        LOCALHOST,
+        httpserver.port,
+        verify_certificate=False
+    )
+
+    wp_config = WorkPackageConfig(
+        name="wp",
+        syf_config=FeederConfigs([]),
+        intervention=InterventionConfig(
+            base_work_package_id="abc",
+            year_range=YearRange(2020, 2025),
+            intervention_type=InterventionClass.DISTRIBUTION_TAP_OPTIMIZATION,
+            allocation_limit_per_year=5,
+            candidate_generation=CandidateGenerationConfig(
+                type=CandidateGenerationType.TAP_OPTIMIZATION,
+                average_voltage_spread_threshold=40,
+                voltage_under_limit_hours_threshold=1,
+                voltage_over_limit_hours_threshold=2,
+                tap_weighting_factor_lower_threshold=-0.3,
+                tap_weighting_factor_upper_threshold=0.4
+            )
+        )
+    )
+    json_config = eas_client.work_package_config_to_json(wp_config)
+
+    assert json_config["intervention"] == {
+        "baseWorkPackageId": "abc",
+        "yearRange": {
+            "maxYear": 2025,
+            "minYear": 2020
+        },
+        "interventionType": "DISTRIBUTION_TAP_OPTIMIZATION",
+        "candidateGeneration": {
+            "type": "TAP_OPTIMIZATION",
+            "interventionCriteriaName": None,
+            "averageVoltageSpreadThreshold": 40,
+            "voltageUnderLimitHoursThreshold": 1,
+            "voltageOverLimitHoursThreshold": 2,
+            "tapWeightingFactorLowerThreshold": -0.3,
+            "tapWeightingFactorUpperThreshold": 0.4,
+        },
+        "allocationCriteria": None,
+        "specificAllocationInstance": None,
+        "phaseRebalanceProportions": None,
+        "dvms": None,
+        "allocationLimitPerYear": 5
+    }