EnergySystemsModellingLab · tsmbland · Aug 25, 2026 · Aug 25, 2026
diff --git a/docs/release_notes/upcoming.md b/docs/release_notes/upcoming.md
@@ -36,6 +36,7 @@ ready to be released, carry out the following steps:
 - The `addition_limit` column in `process_investment_constraints.csv` is now optional ([#1427])
 - Memory usage and performance has been drastically improved for divisible assets with many units
   ([#1464])
+- `asset_capacities.csv` now reports total and mothballed capacity and unit counts ([#1461])
 
 ## Breaking changes
 

diff --git a/schemas/output/asset_capacities.yaml b/schemas/output/asset_capacities.yaml
@@ -13,4 +13,10 @@ fields:
     description: The total capacity of the asset in this year
   - name: num_units
     type: integer
-    description: The number of units making up the asset in this year
+    description: The total number of units making up the asset in this year
+  - name: mothballed_capacity
+    type: number
+    description: The capacity of the asset that is mothballed in this year
+  - name: mothballed_units
+    type: integer
+    description: The number of units that are mothballed in this year
diff --git a/src/asset.rs b/src/asset.rs
@@ -9,8 +9,8 @@ use crate::region::RegionID;
 use crate::simulation::PriceMap;
 use crate::time_slice::{TimeSliceID, TimeSliceSelection};
 use crate::units::{
-    Activity, ActivityPerCapacity, Capacity, FlowPerActivity, MoneyPerActivity, MoneyPerCapacity,
-    MoneyPerFlow, UnitType, Year,
+    Activity, ActivityPerCapacity, Capacity, Dimensionless, FlowPerActivity, MoneyPerActivity,
+    MoneyPerCapacity, MoneyPerFlow, UnitType, Year,
 };
 use anyhow::{Context, Result, ensure};
 use indexmap::IndexMap;
@@ -834,6 +834,11 @@ impl Asset {
         events.iter().map(|event| event.num_units).sum()
     }
 
+    /// Get the capacity which is mothballed.
+    pub fn mothballed_capacity(&self) -> Capacity {
+        self.capacity().unit_size() * Dimensionless(self.get_num_mothballed_units() as f64)
+    }
+
     /// Get the remaining number of units that are not mothballed.
     ///
     /// For non-commissioned assets, this always returns the total number of units.
@@ -1612,6 +1617,10 @@ mod tests {
         assert_eq!(commissioned_multi_unit.num_units(), 3);
         let asset = commissioned_multi_unit.with_mothballed_units(num_mothballed, Some(2020));
         assert_eq!(asset.get_num_mothballed_units(), num_mothballed);
+        assert_eq!(
+            asset.mothballed_capacity(),
+            Capacity(4.0 * num_mothballed as f64)
+        );
         assert_eq!(asset.get_num_nonmothballed_units(), 3 - num_mothballed);
         assert_eq!(asset.has_any_mothballed_units(), num_mothballed > 0);
     }

diff --git a/src/output.rs b/src/output.rs
@@ -166,6 +166,8 @@ struct AssetCapacityRow {
     asset_id: AssetID,
     capacity: Capacity,
     num_units: u32,
+    mothballed_capacity: Capacity,
+    mothballed_units: u32,
 }
 
 /// Represents the flow-related data in a row of the commodity flows CSV file.
@@ -638,6 +640,8 @@ impl DataWriter {
                 asset_id: asset.id().unwrap(),
                 capacity: asset.total_capacity(),
                 num_units: asset.capacity().num_units(),
+                mothballed_capacity: asset.mothballed_capacity(),
+                mothballed_units: asset.get_num_mothballed_units(),
             };
             self.asset_capacities.serialize(row)?;
         }
@@ -709,7 +713,9 @@ impl DataWriter {
 mod tests {
     use super::*;
     use crate::asset::AssetPool;
-    use crate::fixture::{appraisal_output, asset, assets, commodity_id, region_id, time_slice};
+    use crate::fixture::{
+        appraisal_output, asset, assets, commodity_id, multi_unit_asset, region_id, time_slice,
+    };
     use crate::simulation::investment::appraisal::AppraisalOutput;
     use crate::time_slice::TimeSliceID;
     use indexmap::indexmap;
@@ -761,6 +767,46 @@ mod tests {
             asset_id: asset.id().unwrap(),
             capacity: asset.total_capacity(),
             num_units: 1,
+            mothballed_capacity: Capacity(0.0),
+            mothballed_units: 0,
+        };
+        let records: Vec<AssetCapacityRow> =
+            csv::Reader::from_path(dir.path().join(ASSET_CAPACITIES_FILE_NAME))
+                .unwrap()
+                .into_deserialize()
+                .try_collect()
+                .unwrap();
+        assert_equal(records, iter::once(expected));
+    }
+
+    #[rstest]
+    fn write_asset_capacities_with_mothballed_units(multi_unit_asset: Asset) {
+        let milestone_year = 2020;
+        let dir = tempdir().unwrap();
+        let mut assets = AssetPool::new();
+        assets.commission_new(2010, &mut vec![multi_unit_asset.into()]);
+        let asset = assets
+            .iter()
+            .next()
+            .unwrap()
+            .clone()
+            .with_mothballed_units(1, Some(milestone_year));
+
+        {
+            let mut writer = DataWriter::create(dir.path(), dir.path(), false).unwrap();
+            writer
+                .write_asset_capacities(milestone_year, std::slice::from_ref(&asset))
+                .unwrap();
+            writer.flush().unwrap();
+        }
+
+        let expected = AssetCapacityRow {
+            milestone_year,
+            asset_id: asset.id().unwrap(),
+            capacity: Capacity(12.0),
+            num_units: 3,
+            mothballed_capacity: Capacity(4.0),
+            mothballed_units: 1,
         };
         let records: Vec<AssetCapacityRow> =
             csv::Reader::from_path(dir.path().join(ASSET_CAPACITIES_FILE_NAME))

diff --git a/tests/data/circularity/asset_capacities.csv b/tests/data/circularity/asset_capacities.csv
@@ -1,46 +1,46 @@
-milestone_year,asset_id,capacity,num_units
-2020,0,4010.2,1
-2020,1,1738.05,1
-2020,2,3789.64,1
-2020,3,716.5,1
-2020,4,573.9,1
-2020,5,3.964844,1
-2020,6,2.999,1
-2020,7,1.0,1
-2020,8,31.54,1
-2020,9,451.91,1
-2020,10,176.58,1
-2020,11,20.99,1
-2020,12,15.0,1
-2020,13,2900.0,1
-2020,14,399.98,1
-2030,0,4010.2,1
-2030,1,1738.05,1
-2030,2,3789.64,1
-2030,5,3.964844,1
-2030,6,2.999,1
-2030,13,2900.0,1
-2030,14,399.98,1
-2030,15,802.563016789748,28
-2030,16,1849.28399075358,36
-2030,17,3680.183145405077,26
-2030,18,298.6475820926018,57
-2030,19,2944.1465163240614,16
-2030,20,165.3505808753475,27
-2040,5,3.964844,1
-2040,6,2.999,1
-2040,16,1849.28399075358,36
-2040,18,298.6475820926018,57
-2040,19,1288.064100891777,7
-2040,20,165.3505808753475,27
-2040,21,942.563016229748,28
-2040,22,2198.390989008045,39
-2040,23,34.19605824723177,15
-2040,24,5.471369319196239,6
-2040,25,9.118948865327066,9
-2040,26,132.08198143321187,15
-2040,27,453.28514602874316,33
-2040,28,972.485651665613,26
-2040,29,2349.6972514094086,33
-2040,30,475.9494033301804,33
-2040,31,2627.9227668603858,37
+milestone_year,asset_id,capacity,num_units,mothballed_capacity,mothballed_units
+2020,0,4010.2,1,0.0,0
+2020,1,1738.05,1,0.0,0
+2020,2,3789.64,1,0.0,0
+2020,3,716.5,1,0.0,0
+2020,4,573.9,1,0.0,0
+2020,5,3.964844,1,0.0,0
+2020,6,2.999,1,0.0,0
+2020,7,1.0,1,0.0,0
+2020,8,31.54,1,0.0,0
+2020,9,451.91,1,0.0,0
+2020,10,176.58,1,0.0,0
+2020,11,20.99,1,0.0,0
+2020,12,15.0,1,0.0,0
+2020,13,2900.0,1,0.0,0
+2020,14,399.98,1,0.0,0
+2030,0,4010.2,1,0.0,0
+2030,1,1738.05,1,0.0,0
+2030,2,3789.64,1,0.0,0
+2030,5,3.964844,1,0.0,0
+2030,6,2.999,1,0.0,0
+2030,13,2900.0,1,0.0,0
+2030,14,399.98,1,0.0,0
+2030,15,802.563016789748,28,0.0,0
+2030,16,1849.28399075358,36,0.0,0
+2030,17,3680.183145405077,26,0.0,0
+2030,18,298.6475820926018,57,0.0,0
+2030,19,2944.1465163240614,16,0.0,0
+2030,20,165.3505808753475,27,0.0,0
+2040,5,3.964844,1,0.0,0
+2040,6,2.999,1,0.0,0
+2040,16,1849.28399075358,36,0.0,0
+2040,18,298.6475820926018,57,0.0,0
+2040,19,1288.064100891777,7,0.0,0
+2040,20,165.3505808753475,27,0.0,0
+2040,21,942.563016229748,28,0.0,0
+2040,22,2198.390989008045,39,0.0,0
+2040,23,34.19605824723177,15,0.0,0
+2040,24,5.471369319196239,6,0.0,0
+2040,25,9.118948865327066,9,0.0,0
+2040,26,132.08198143321187,15,0.0,0
+2040,27,453.28514602874316,33,0.0,0
+2040,28,972.485651665613,26,0.0,0
+2040,29,2349.6972514094086,33,0.0,0
+2040,30,475.9494033301804,33,0.0,0
+2040,31,2627.9227668603858,37,0.0,0
diff --git a/tests/data/circularity_npv/asset_capacities.csv b/tests/data/circularity_npv/asset_capacities.csv
@@ -1,46 +1,46 @@
-milestone_year,asset_id,capacity,num_units
-2020,0,4010.2,1
-2020,1,1738.05,1
-2020,2,3789.64,1
-2020,3,716.5,1
-2020,4,573.9,1
-2020,5,3.964844,1
-2020,6,2.999,1
-2020,7,1.0,1
-2020,8,31.54,1
-2020,9,451.91,1
-2020,10,176.58,1
-2020,11,20.99,1
-2020,12,15.0,1
-2020,13,2900.0,1
-2020,14,399.98,1
-2030,0,4010.2,1
-2030,1,1738.05,1
-2030,2,3789.64,1
-2030,5,3.964844,1
-2030,6,2.999,1
-2030,13,2900.0,1
-2030,14,399.98,1
-2030,15,802.563016789748,28
-2030,16,1849.28399075358,36
-2030,17,3680.183145405077,26
-2030,18,298.6475820926018,57
-2030,19,2944.1465163240614,16
-2030,20,165.3505808753475,27
-2040,5,3.964844,1
-2040,6,2.999,1
-2040,16,1849.28399075358,36
-2040,18,298.6475820926018,57
-2040,19,1288.064100891777,7
-2040,20,165.3505808753475,27
-2040,21,942.563016229748,28
-2040,22,2198.390989008045,39
-2040,23,34.19605824723177,15
-2040,24,5.471369319196239,6
-2040,25,9.118948865327066,9
-2040,26,132.08198143321187,15
-2040,27,453.28514602874316,33
-2040,28,972.485651665613,26
-2040,29,2349.6972514094086,33
-2040,30,475.9494033301804,33
-2040,31,2627.9227668603858,37
+milestone_year,asset_id,capacity,num_units,mothballed_capacity,mothballed_units
+2020,0,4010.2,1,0.0,0
+2020,1,1738.05,1,0.0,0
+2020,2,3789.64,1,0.0,0
+2020,3,716.5,1,0.0,0
+2020,4,573.9,1,0.0,0
+2020,5,3.964844,1,0.0,0
+2020,6,2.999,1,0.0,0
+2020,7,1.0,1,0.0,0
+2020,8,31.54,1,0.0,0
+2020,9,451.91,1,0.0,0
+2020,10,176.58,1,0.0,0
+2020,11,20.99,1,0.0,0
+2020,12,15.0,1,0.0,0
+2020,13,2900.0,1,0.0,0
+2020,14,399.98,1,0.0,0
+2030,0,4010.2,1,0.0,0
+2030,1,1738.05,1,0.0,0
+2030,2,3789.64,1,0.0,0
+2030,5,3.964844,1,0.0,0
+2030,6,2.999,1,0.0,0
+2030,13,2900.0,1,0.0,0
+2030,14,399.98,1,0.0,0
+2030,15,802.563016789748,28,0.0,0
+2030,16,1849.28399075358,36,0.0,0
+2030,17,3680.183145405077,26,0.0,0
+2030,18,298.6475820926018,57,0.0,0
+2030,19,2944.1465163240614,16,0.0,0
+2030,20,165.3505808753475,27,0.0,0
+2040,5,3.964844,1,0.0,0
+2040,6,2.999,1,0.0,0
+2040,16,1849.28399075358,36,0.0,0
+2040,18,298.6475820926018,57,0.0,0
+2040,19,1288.064100891777,7,0.0,0
+2040,20,165.3505808753475,27,0.0,0
+2040,21,942.563016229748,28,0.0,0
+2040,22,2198.390989008045,39,0.0,0
+2040,23,34.19605824723177,15,0.0,0
+2040,24,5.471369319196239,6,0.0,0
+2040,25,9.118948865327066,9,0.0,0
+2040,26,132.08198143321187,15,0.0,0
+2040,27,453.28514602874316,33,0.0,0
+2040,28,972.485651665613,26,0.0,0
+2040,29,2349.6972514094086,33,0.0,0
+2040,30,475.9494033301804,33,0.0,0
+2040,31,2627.9227668603858,37,0.0,0
diff --git a/tests/data/missing_commodity/asset_capacities.csv b/tests/data/missing_commodity/asset_capacities.csv
@@ -1,23 +1,23 @@
-milestone_year,asset_id,capacity,num_units
-2020,0,4002.26,1
-2020,1,3782.13,1
-2020,2,3.964844,1
-2020,3,2.43,1
-2020,4,2900.0,1
-2020,5,399.98,1
-2030,0,4002.26,1
-2030,1,3782.13,1
-2030,2,3.964844,1
-2030,3,2.43,1
-2030,4,2900.0,1
-2030,5,399.98,1
-2030,6,1849.28399075358,36
-2030,7,4.582296913025608,13
-2030,8,178.91233238712087,66
-2030,9,189.58177552751894,30
-2040,6,1849.28399075358,36
-2040,8,178.91233238712087,66
-2040,9,189.58177552751894,30
-2040,10,2198.390989008045,39
-2040,11,2420.9001984218153,34
-2040,12,2556.897827215511,36
+milestone_year,asset_id,capacity,num_units,mothballed_capacity,mothballed_units
+2020,0,4002.26,1,0.0,0
+2020,1,3782.13,1,0.0,0
+2020,2,3.964844,1,0.0,0
+2020,3,2.43,1,0.0,0
+2020,4,2900.0,1,0.0,0
+2020,5,399.98,1,0.0,0
+2030,0,4002.26,1,0.0,0
+2030,1,3782.13,1,0.0,0
+2030,2,3.964844,1,0.0,0
+2030,3,2.43,1,0.0,0
+2030,4,2900.0,1,0.0,0
+2030,5,399.98,1,0.0,0
+2030,6,1849.28399075358,36,0.0,0
+2030,7,4.582296913025608,13,0.0,0
+2030,8,178.91233238712087,66,0.0,0
+2030,9,189.58177552751894,30,0.0,0
+2040,6,1849.28399075358,36,0.0,0
+2040,8,178.91233238712087,66,0.0,0
+2040,9,189.58177552751894,30,0.0,0
+2040,10,2198.390989008045,39,0.0,0
+2040,11,2420.9001984218153,34,0.0,0
+2040,12,2556.897827215511,36,0.0,0