ReEDS-Model · Max-Vanatta · Jun 1, 2026 · Jun 3, 2026 · Jun 4, 2026 · Jun 4, 2026
diff --git a/cases.csv b/cases.csv
@@ -324,6 +324,8 @@ GSw_TransCapMaxAllTypes,[GW] maximum transmission capacity allowed across each i
 GSw_TransCapMaxTypes,Transmission types to limit according to GSw_TransCapMaxEachType and GSw_TransCapMaxAllTypes [0 = none; 1 = all; 2 = VSC; 3 = all DC],0; 1; 2; 3,1,
 GSw_TransConductor,Which conductor to assume for new AC transmission ('acss' is a mix of ACSS and ACSR as specified by the MISO Transmission Cost Estimation Guide; 'acsr' is just ACSR),^(acss|acsr)$,acsr,
 GSw_TransIntraCost,[USD2004/kW] intra-zone network reinforcement cost for all technologies (100 USD2022/kW using gas cost from slide 14 of https://emp.lbl.gov/publications/generator-interconnection-costs),N/A,65,
+GSw_RegIntraCurve,Represent intra-zone network reinforcement as a regional increasing-cost supply curve instead of the flat GSw_TransIntraCost adder; requires GSw_TransIntraCost>0,0; 1,0,
+GSw_POIUpperCost,[USD2004/kW] cost of the unlimited backstop bin (bin_upper) applied to POI / network reinforcement above the finite binned capacities; only active when GSw_RegIntraCurve=1,float,1177,
 GSw_TransInvMaxLongTerm,[TW-mile/year] maximum transmission capacity investment per year IN/AFTER firstyear_trans_longterm (constraint is OFF if set to 0 meaning unlimited trans investment; annual max since 2009 is ~3.64),N/A,0,
 GSw_TransInvMaxNearTerm,[TW-mile/year] maximum transmission capacity investment per year BEFORE firstyear_trans_longterm (constraint is OFF if set to 0 meaning unlimited trans investment; annual mean since 2009 is ~1.4),float,1.4,
 GSw_TransInvNearTerm,Indicate whether to allow transmission investment before firstyear_trans_longterm,0; 1,0,

diff --git a/cases_test.csv b/cases_test.csv
@@ -1,65 +1,66 @@
-,Default Value,Pacific,USA_defaults,Mid_Case,USA_decarb,github_Pacific,github_Everything,github_MA_county_CC,Pacific_CC,Pacific_weks,Pacific_full_year,Interday_storage,Pacific_2020,Pacific_rep15,WY_county,WECC_county,PJM_county_CC,NYVT_mixed,OR_water,MonteCarlo_Random,MonteCarlo_LHS,Everything,Simple,USA_fast,USA_faster,Pacific_DR,Pacific_MGA,Pacific_LoadSite95,MARICTNYNJPAOH_Offshore,R2P
-ignore,1,0,,,,,,,,,,,,,,,,,,,,,,,,,,,,
-GSw_Region,cendiv/Pacific,,country/USA,country/USA,country/USA,,st/ID.WY.NE.IA.IL,st/MA,,,,,,,st/WY,interconnect/western,transreg/PJM,st/NY.VT,st/OR,st/NE.NY.PA,st/NE.NY.PA,st/ID.WY.NE.IA.IL,st/KS,country/USA,country/USA,,,,st/MA.RI.CT.NY.NJ.PA.OH,
-endyear,2032,,2050,2050,2050,2029,2060,2026,,,,,,,,,,,2035,2030,2030,2060,2035,2050,2050,,,,,
-yearset,,,,,,,2010..2060..10,,,,,,,,,,,,,2010..2050..5,2010..2050..5,2010..2060..10,,,2010_2025_2050,,,,,
-GSw_ZoneSet,,,,,,,z54,z3109,,,,,,,z3109,z3109,z3109,PJMcounty,,,,z54,,z54,z48,,,,,
-GSw_GasCurve,2,,1,1,,,,,,,,,,,,,,,,,,,,1,1,,,,,
-GSw_Geothermal,,,,2,,,,,,,,,,,,,,,,,,,0,,0,,,,,
-GSw_GrowthPenalties,,,,1,,,,,,,,,,,,,,,,,,,,,,,,,,
-GSw_Upstream,,,,1,,,,,,,,,,,,,,,,,,,,,,,,,,
-GSw_TransHurdleRate,,,,1,,,,,,,,,,,,,,,,,,,,,,,,,,
-distpvscen,,,,,stscen2023_mid_case_95_by_2035,,,,,,,,,,,,,,,,,,,,,,,,,
-GSw_AnnualCap,,,,,2,,1,,,,,,,,,,,,,,,1,,,,,,,,
-GSw_AnnualCapScen,,,,,start2024_90pct2035_100pct2045,,start2027_95pct2035,,,,,,,,,,,,,,,start2027_95pct2035,,,,,,,,
-GSw_LoadProfiles,,,,,EER2025_100by2050,EER2025_IRAlow,EER2025_IRAlow,EER2025_IRAlow,,,,,historic,,,,,,,,,EER2025_100by2050,,,,historic,,,,
-GSw_NG_CRF_penalty,,,,,ramp_2045,,ramp_2023_2035,,,,,,,,,,,,,,,ramp_2023_2035,,,,,,,,
-GSw_PRM_NetImportLimit,,,,,0,,,,,,,,,,,,,,,,,,,,,,,,,
-GSw_RetirePenalty,,,,,0,,,,,,,,,,,,,,,,,,,,,,,,,
-GSw_FakeData,,,,,,1,1,1,,,,,,,,,,,,,,,,,,,,,,
-GSw_PRM_CapCredit,,,,,,,,1,1,,,,,,,,1,,,,,,,,,,,,,
-GSw_PRM_scenario,,,,,,,,,static,,,,,,,,static,,,,,,,,,,,,,
-GSw_PRM_UpdateMethod,,,,,,,,,1,,,,,,,,,,,,,,,,,,,,,
-GSw_HourlyType,,,,,,,,,,wek,year,,,,,,,,,,,,,,,,,,,
-GSw_InterDayLinkage,,,,,,,,,,,,1,,,,,,,,,,,,,,,,,,
-GSw_HourlyWeatherYears,,,,,,,2012_2013,,,,,,2020,2007_2008_2009_2010_2011_2012_2013_2016_2017_2018_2019_2020_2021_2022_2023,,,,,,,,2012_2013,,,,2018,,,,
-GSw_HourlyClusterMapMethod,,,,,,,,,,,,,,bestfirst,,,,,,,,,,,,,,,,
-GSw_WaterCapacity,,,,,,,,,,,,,,,,,,,1,,,,,,,,,,,
-GSw_WaterMain,,,,,,,,,,,,,,,,,,,1,,,,,,,,,,,
-GSw_WaterUse,,,,,,,,,,,,,,,,,,,1,,,,,,,,,,,
-resource_adequacy_years,,,,,,,2011_2012_2013_2021_2022_2023,,,,,,,,,,,,,,,2011_2012_2013_2021_2022_2023,,,,,,,,
-GSw_HourlyClusterAlgorithm,,,,,,,,,,,,,,,,,,,,user,user,,,,,,,,,
-MCS_runs,,,,,,,,,,,,,,,,,,,,2,2,,,,,,,,,
-MCS_dist_groups,,,,,,,,,,,,,,,,,,,,tech.hydro.nuclear.gas.coal.load_country,upv_tri.nuclear_tri.ng_fuel_price_tri.load_country_unif,,,,,,,,,
-MCS_lhs,,,,,,,,,,,,,,,,,,,,,1,,,,,,,,,
-GSw_PRM_StressIterateMax,,,,,,,,0,,,,,,,,0,0,,,1,1,,,,,,,,,
-GSw_ReducedResource,,,,,,,1,,,,,,,,,,,,,,,1,,,,,,,,
-GSw_SitingUPV,,,,,,limited,limited,limited,,,,,,,,,,,,,,limited,,,,,,,,
-GSw_SitingWindOfs,,,,,,limited,limited,limited,,,,,,,,,,,,,,open,,,,,,,,
-GSw_SitingWindOns,,,,,,limited,limited,limited,,,,,,,,,,,,,,limited,,,,,,,,
-GSw_TransScen,,,,,,,NTP_MT,,,,,,,,,,,,,,,NTP_MT,,,,,,,,
-GSw_CO2_Detail,,,,,,,1,,,,,,,,,,,,,,,1,,,,,,,,
-GSw_DAC,,,,,,,1,,,,,,,,,,,,,,,1,,,,,,,,
-GSw_NoFossilOffsetCDR,,,,,,,1,,,,,,,,,,,,,,,1,,,,,,,,
-GSw_Biopower,,,,,,,,,,,,,,,,,,,,,,,0,,0,,,,,
-GSw_HourlyChunkLengthRep,,,,,,,,,,,,,,,,,,,,,,,6,4,4,,,,,
-GSw_HourlyChunkLengthStress,,,,,,,,,,,,,,,,,,,,,,,6,4,4,,,,,
-GSw_LfillGas,,,,,,,,,,,,,,,,,,,,,,,0,,0,,,,,
-GSw_Nuclear,,,,,,,,,,,,,,,,,,,,,,,0,,0,,,,,
-GSw_OpRes,,,,,,,,,,,,,,,,,,,,,,,0,,0,,,,,
-GSw_StartCost,,,,,,,,,,,,,,,,,,,,,,,0,0,0,,,,,
-GSw_H2,,,,,,,,,,,,,,,,,,,,,,,,0,0,,,,,
-GSw_H2_PTC,,,,,,,,,,,,,,,,,,,,,,,,0,0,,,,,
-GSw_H2Combustion,,,,,,,,,,,,,,,,,,,,,,,,,0,,,,,
-GSw_DRShed,,,,,,,,,,,,,,,,,,,,,,,,,,1,,,,
-GSw_MGA_CostDelta,,,,,,,,,,,,,,,,,,,,,,,,,,,0.01,,,
-GSw_LoadSiteCF,,,,,,,,,,,,,,,,,,,,,,,,,,,,0.95,,
-GSw_OffshoreZones,,,,,,,,,,,,,,,,,,,,,,,,,,,,,1,
-GSw_OffshoreBackbone,,,,,,,,,,,,,,,,,,,,,,,,,,,,,1,
-GSw_OffshoreBackflow,,,,,,,,,,,,,,,,,,,,,,,,,,,,,1,
-pras_agg_ogs_lfillgas,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,1
-pras_existing_unit_size,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,0
-pras_scheduled_outage,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,0
-pras_unitsize_source,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,r2x
-pras_vre_combine,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,1
-pras_samples,,,,,,10,10,10,,,,,,,,,,,,,,,,10,10,,,,,
+,Default Value,Pacific,USA_defaults,Mid_Case,USA_decarb,github_Pacific,github_Everything,github_MA_county_CC,Pacific_CC,Pacific_weks,Pacific_full_year,Interday_storage,Pacific_2020,Pacific_rep15,WY_county,WECC_county,PJM_county_CC,NYVT_mixed,OR_water,MonteCarlo_Random,MonteCarlo_LHS,Everything,Simple,USA_fast,USA_faster,Pacific_DR,Pacific_MGA,Pacific_LoadSite95,MARICTNYNJPAOH_Offshore,R2P,Pacific_ReinfCurve
+ignore,1,0,,,,,,,,,,,,,,,,,,,,,,,,,,,,,0
+GSw_Region,cendiv/Pacific,,country/USA,country/USA,country/USA,,st/ID.WY.NE.IA.IL,st/MA,,,,,,,st/WY,interconnect/western,transreg/PJM,st/NY.VT,st/OR,st/NE.NY.PA,st/NE.NY.PA,st/ID.WY.NE.IA.IL,st/KS,country/USA,country/USA,,,,st/MA.RI.CT.NY.NJ.PA.OH,,
+endyear,2032,,2050,2050,2050,2029,2060,2026,,,,,,,,,,,2035,2030,2030,2060,2035,2050,2050,,,,,,
+yearset,,,,,,,2010..2060..10,,,,,,,,,,,,,2010..2050..5,2010..2050..5,2010..2060..10,,,2010_2025_2050,,,,,,
+GSw_ZoneSet,,,,,,,z54,z3109,,,,,,,z3109,z3109,z3109,PJMcounty,,,,z54,,z54,z48,,,,,,
+GSw_GasCurve,2,,1,1,,,,,,,,,,,,,,,,,,,,1,1,,,,,,
+GSw_Geothermal,,,,2,,,,,,,,,,,,,,,,,,,0,,0,,,,,,
+GSw_GrowthPenalties,,,,1,,,,,,,,,,,,,,,,,,,,,,,,,,,
+GSw_Upstream,,,,1,,,,,,,,,,,,,,,,,,,,,,,,,,,
+GSw_TransHurdleRate,,,,1,,,,,,,,,,,,,,,,,,,,,,,,,,,
+distpvscen,,,,,stscen2023_mid_case_95_by_2035,,,,,,,,,,,,,,,,,,,,,,,,,,
+GSw_AnnualCap,,,,,2,,1,,,,,,,,,,,,,,,1,,,,,,,,,
+GSw_AnnualCapScen,,,,,start2024_90pct2035_100pct2045,,start2027_95pct2035,,,,,,,,,,,,,,,start2027_95pct2035,,,,,,,,,
+GSw_LoadProfiles,,,,,EER2025_100by2050,EER2025_IRAlow,EER2025_IRAlow,EER2025_IRAlow,,,,,historic,,,,,,,,,EER2025_100by2050,,,,historic,,,,,
+GSw_NG_CRF_penalty,,,,,ramp_2045,,ramp_2023_2035,,,,,,,,,,,,,,,ramp_2023_2035,,,,,,,,,
+GSw_PRM_NetImportLimit,,,,,0,,,,,,,,,,,,,,,,,,,,,,,,,,
+GSw_RetirePenalty,,,,,0,,,,,,,,,,,,,,,,,,,,,,,,,,
+GSw_FakeData,,,,,,1,1,1,,,,,,,,,,,,,,,,,,,,,,,
+GSw_PRM_CapCredit,,,,,,,,1,1,,,,,,,,1,,,,,,,,,,,,,,
+GSw_PRM_scenario,,,,,,,,,static,,,,,,,,static,,,,,,,,,,,,,,
+GSw_PRM_UpdateMethod,,,,,,,,,1,,,,,,,,,,,,,,,,,,,,,,
+GSw_HourlyType,,,,,,,,,,wek,year,,,,,,,,,,,,,,,,,,,,
+GSw_InterDayLinkage,,,,,,,,,,,,1,,,,,,,,,,,,,,,,,,,
+GSw_HourlyWeatherYears,,,,,,,2012_2013,,,,,,2020,2007_2008_2009_2010_2011_2012_2013_2016_2017_2018_2019_2020_2021_2022_2023,,,,,,,,2012_2013,,,,2018,,,,,
+GSw_HourlyClusterMapMethod,,,,,,,,,,,,,,bestfirst,,,,,,,,,,,,,,,,,
+GSw_WaterCapacity,,,,,,,,,,,,,,,,,,,1,,,,,,,,,,,,
+GSw_WaterMain,,,,,,,,,,,,,,,,,,,1,,,,,,,,,,,,
+GSw_WaterUse,,,,,,,,,,,,,,,,,,,1,,,,,,,,,,,,
+resource_adequacy_years,,,,,,,2011_2012_2013_2021_2022_2023,,,,,,,,,,,,,,,2011_2012_2013_2021_2022_2023,,,,,,,,,
+GSw_HourlyClusterAlgorithm,,,,,,,,,,,,,,,,,,,,user,user,,,,,,,,,,
+MCS_runs,,,,,,,,,,,,,,,,,,,,2,2,,,,,,,,,,
+MCS_dist_groups,,,,,,,,,,,,,,,,,,,,tech.hydro.nuclear.gas.coal.load_country,upv_tri.nuclear_tri.ng_fuel_price_tri.load_country_unif,,,,,,,,,,
+MCS_lhs,,,,,,,,,,,,,,,,,,,,,1,,,,,,,,,,
+GSw_PRM_StressIterateMax,0,,,,,,,0,,,,,,,,0,0,,,1,1,,,,,,,,,,
+GSw_ReducedResource,,,,,,,1,,,,,,,,,,,,,,,1,,,,,,,,,
+GSw_SitingUPV,,,,,,limited,limited,limited,,,,,,,,,,,,,,limited,,,,,,,,,
+GSw_SitingWindOfs,,,,,,limited,limited,limited,,,,,,,,,,,,,,open,,,,,,,,,
+GSw_SitingWindOns,,,,,,limited,limited,limited,,,,,,,,,,,,,,limited,,,,,,,,,
+GSw_TransScen,,,,,,,NTP_MT,,,,,,,,,,,,,,,NTP_MT,,,,,,,,,
+GSw_CO2_Detail,,,,,,,1,,,,,,,,,,,,,,,1,,,,,,,,,
+GSw_DAC,,,,,,,1,,,,,,,,,,,,,,,1,,,,,,,,,
+GSw_NoFossilOffsetCDR,,,,,,,1,,,,,,,,,,,,,,,1,,,,,,,,,
+GSw_Biopower,,,,,,,,,,,,,,,,,,,,,,,0,,0,,,,,,
+GSw_HourlyChunkLengthRep,,,,,,,,,,,,,,,,,,,,,,,6,4,4,,,,,,
+GSw_HourlyChunkLengthStress,,,,,,,,,,,,,,,,,,,,,,,6,4,4,,,,,,
+GSw_LfillGas,,,,,,,,,,,,,,,,,,,,,,,0,,0,,,,,,
+GSw_Nuclear,,,,,,,,,,,,,,,,,,,,,,,0,,0,,,,,,
+GSw_OpRes,,,,,,,,,,,,,,,,,,,,,,,0,,0,,,,,,
+GSw_StartCost,,,,,,,,,,,,,,,,,,,,,,,0,0,0,,,,,,
+GSw_H2,,,,,,,,,,,,,,,,,,,,,,,,0,0,,,,,,
+GSw_H2_PTC,,,,,,,,,,,,,,,,,,,,,,,,0,0,,,,,,
+GSw_H2Combustion,,,,,,,,,,,,,,,,,,,,,,,,,0,,,,,,
+GSw_DRShed,,,,,,,,,,,,,,,,,,,,,,,,,,1,,,,,
+GSw_MGA_CostDelta,,,,,,,,,,,,,,,,,,,,,,,,,,,0.01,,,,
+GSw_LoadSiteCF,,,,,,,,,,,,,,,,,,,,,,,,,,,,0.95,,,
+GSw_OffshoreZones,,,,,,,,,,,,,,,,,,,,,,,,,,,,,1,,
+GSw_OffshoreBackbone,,,,,,,,,,,,,,,,,,,,,,,,,,,,,1,,
+GSw_OffshoreBackflow,,,,,,,,,,,,,,,,,,,,,,,,,,,,,1,,
+pras_agg_ogs_lfillgas,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,1,
+pras_existing_unit_size,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,0,
+pras_scheduled_outage,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,0,
+pras_unitsize_source,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,r2x,
+pras_vre_combine,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,1,
+pras_samples,,,,,,10,10,10,,,,,,,,,,,,,,,,10,10,,,,,,
+GSw_RegIntraCurve,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,1
diff --git a/cases_transmission_test.csv b/cases_transmission_test.csv
@@ -0,0 +1,7 @@
+,Default Value,ERCOT_default,ERCOT_0,ERCOT_regional
+ignore,1,,,0
+endyear,2032,,,
+GSw_Region,interconnect/texas,,,
+GSw_GasCurve,2,,,
+GSw_RegIntraCurve,0,,,1
+GSw_TransIntraCost,,,0.0001,
diff --git a/docs/source/model_documentation.md b/docs/source/model_documentation.md
@@ -1842,6 +1842,9 @@ Substation POIs incur a substation upgrade cost of \$15/kW; transmission line PO
 
 Network reinforcement represents upgrades to the existing transmission network required to avoid congestion when moving power from the POI for a new generator to load centers.
 It is intended to represent the costs associated with interconnection queues, which represent a major bottleneck for the deployment of new wind and solar in the United States. {cite}`gormanGridConnectionBarriers2025`.
+There are two methods for including these costs: a) per-site reinforcement costs with optional flat adders, or b) regional reinforcement cost curves.
+
+##### per-site reinforcement costs
 Network reinforcement costs are approximated by tracing a path along existing transmission lines from each wind/solar POI to a nearby urban center.
 An urban center is defined as the centroid of a ≥100 km<sup>2</sup> urban area from [2020 U.S. Census data](https://www.census.gov/cgi-bin/geo/shapefiles/index.php?year=2025&layergroup=Urban+Areas).
 POIs are assumed to connect to the urban center that minimizes the combined interconnection cost;
@@ -1869,7 +1872,7 @@ Data are for utility-scale PV with open-access siting but are similar for other
 Spur lines and network reinforcement use the same financial multiplier as the generation technology they are associated with.
 
 
-#### Intrazone transmission cost adder for net increases in generation capacity
+##### Intrazone transmission cost adder for net increases in generation capacity
 
 In addition to the interconnection costs described above, a flat intrazone transmission cost adder of \$100/kW is also applied to net increases in generation and AC/DC converter capacity within each model zone.
 This value is taken from historical interconnection costs for fossil gas capacity {cite}`seelGeneratorInterconnectionCosts2023` and is taken to represent a "floor" for network upgrades that are required even if new capacity is added at the optimal location (assuming past additions of fossil capacity have been placed to minimize interconnection costs).
@@ -1878,7 +1881,14 @@ Because new generation capacity is assumed to reuse the network infrastructure f
 
 This generation-technology-neutral intrazone transmission cost adder uses a financial multiplier calculated using a 40-year capital recovery period.
 
+By default the intrazone adder is flat (`GSw_TransIntraCost`, applied to every MW of net new capacity in the zone).
 
+##### regional reinforcement cost curves
+Optionally, reinforcement costs can be represented by regionally specific transmission upgrade curves.
+We derive the regional curves using the same principles of power flow informed capacity interconnection maximization as outlined in {cite}`brownGeneralMethodEstimating2023`.
+In this method, we iteratively maximize the amount of generation capacity that can be installed in a ReEDS region and then upgrade the best value binding transmission system elements.
+To functionally intergrate this upgrade curve, we take the convex hull of this data, producing binned investment costs (e.g., 400 MW of generation capacity is available at \$100/kW, the next 2 GW at \$200/kW, and so on).
+To avoid double counting, when regional curves are active, the site-based reinforcement costs are subtracted from the wind, solar, CSP, and geothermal technologies while retaining the spur line and substation/POI costs.
 
 
 ### Interzonal Transmission

diff --git a/inputs/transmission/README.md b/inputs/transmission/README.md
@@ -16,7 +16,7 @@
 
 - `cost_hurdle_intra.csv`: Hurdle rate for transmission flows [\$/MWh] between ReEDS spatial hierarchy levels.
 
-- `dollaryear.scv`: U.S. dollar year for cost-related input files
+- `dollaryear.csv`: U.S. dollar year for cost-related input files
 
 - `hvdc_existing.csv`: Power capacity and start/end locations of [high-voltage direct current (HVDC) lines](https://en.wikipedia.org/wiki/List_of_HVDC_projects#North_America) in the USA.
 These lines are mapped to ReEDS zone interfaces during input processing.
@@ -59,6 +59,13 @@ Calculated using the [TSC](https://github.nrel.gov/pbrown/TSC) model as describe
 - `newlinks_offshore_backbone.csv`: Candidate connections between offshore zones
   - Similarly formatted files for candidate connections between offshore and coastal land-based zones are found at `inputs/zones/{GSw_ZoneSet}/newlinks_offshore_radial.csv`
 
+- `reinforcement_upgrade_cost_z90.csv`: Cumulative interconnection / network-reinforcement cost curve per ReEDS zone from the [TSC](https://github.nrel.gov/ReEDS/TSC) model (nodal network data as described by [Brown et al.](https://arxiv.org/abs/2308.03612)). One cumulative supply-curve point per row:
+    - `region`: ReEDS zone (must match the zone set's `hierarchy.csv`)
+    - `capacity_GW`: cumulative POI capacity [GW]; the row with zero cumulative cost marks the zone's existing (free) capacity
+    - `cum_cost_$`: cumulative reinforcement cost [USD2024]
+    - `slope_$/kW`: marginal cost from the previous point [USD2024/kW] (informational)
+  - When `GSw_RegIntraCurve = 1`, `reeds/input_processing/transmission.py` builds the curve from this file — one bin per raw segment, no re-segmentation.
+
 - `transmission_cost_ac_500kv_z134.h5`: Example file illustrating the required format when using the transmission upgrade supply curve ([TSC](https://github.nrel.gov/ReEDS/TSC)) method for `GSw_ZoneSet = z134`
   - The full method is not yet supported; when implemented, it will only be supported for a limited number of `GSw_ZoneSet` definitions
 

diff --git a/inputs/transmission/dollaryear.csv b/inputs/transmission/dollaryear.csv
@@ -1,3 +1,4 @@
 filename,US_dollar_year
 transmission_cost_distance.csv,2024
 transmission_cost_distance_lines.csv,2024
+reinforcement_upgrade_cost_z90.csv,2024
diff --git a/inputs/transmission/raw_interconnection_TSC_data.csv b/inputs/transmission/raw_interconnection_TSC_data.csv
@@ -0,0 +1,36 @@
+region,capacity_GW,cum_cost_$,slope_$/kW
+p64,18.395181,0.0,
+p64,18.694236,114463990.559,382.7523049572831
+p64,20.748264,907304811.9760001,385.9931906561159
+p64,22.622047,1643645994.469,392.9703612921028
+p64,23.772958,2628994319.4110003,856.1464135298033
+p64,24.000448,3067805398.096,1928.9246942063426
+p64,24.02535,3151327929.3240004,3354.0491216768633
+p64,24.025789,3175874437.8830004,55914.59808427253
+p60,10.122161,0.0,
+p60,12.4329,767976587.457,1362.1436457201123
+p60,12.476908,855604755.6110001,1991.1872421832484
+p60,12.754935,1563955258.588,2547.7759461383266
+p60,12.78238,1671172354.938,3906.616737110558
+p65,16.944069,0.0,
+p65,18.384130000000003,241383980.851,167.62066388229346
+p65,18.817252,602090435.2969999,832.8056631757383
+p65,18.894895,837427049.8929999,3031.008778589109
+p65,19.289016,5245451591.69,11184.44473092532
+p63,23.089008999999997,0.0,
+p63,28.493168,386234699.833,71.46989935584793
+p63,28.961292,687741382.969,644.0743972451749
+p63,29.187818,1233062578.915,2407.322761828667
+p63,29.491341000000002,2193757029.823,3165.145477963758
+p63,29.742103999999998,4116689919.9049997,7668.327823809866
+p61,4.410552,0.0,
+p61,6.210939000000001,248345397.42,137.940008131585
+p61,6.624522,332116199.004,202.5489480563761
+p61,7.396416,738882603.4430001,526.9718438529122
+p61,7.962903,1487868578.0720003,1322.1591574546296
+p62,5.357201,0.0,
+p62,5.940863,1187948171.1699998,2035.3358127991871
+p62,6.078123,1517508685.445,2400.9945670625184
+p62,6.079435999999999,1803040982.712,217465.5729376013
+p67,1,0.0,
+p67,1,50000000.0,50000.0