diff --git a/src/constraints/capacity.jl b/src/constraints/capacity.jl
index 5eecdce9..dccd61ab 100644
--- a/src/constraints/capacity.jl
+++ b/src/constraints/capacity.jl
@@ -1,19 +1,7 @@
 export add_capacity_constraints!
 
 """
-add_capacity_constraints!(model,
-                          graph,
-                          dataframes,
-                          df_flows,
-                          flow,
-                          Ai,
-                          investable_assets_using_simple_method,
-                          Asb,
-                          assets_investment,
-                          accumulated_units,
-                          outgoing_flow_highest_out_resolution,
-                          incoming_flow_highest_in_resolution
-                          )
+add_capacity_constraints!(model, graph,...)
 
 Adds the capacity constraints for all asset types to the model
 """
@@ -28,6 +16,7 @@ function add_capacity_constraints!(
     decommissionable_assets_using_simple_method,
     decommissionable_assets_using_compact_method,
     V_all,
+    accumulated_units_lookup,
     accumulated_set_using_compact_method_lookup,
     Asb,
     assets_investment,
@@ -76,7 +65,7 @@ function add_capacity_constraints!(
                         1.0,
                     ) *
                     graph[row.asset].capacity *
-                    accumulated_units[row.year, row.asset]
+                    accumulated_units[accumulated_units_lookup[(row.asset, row.year)]]
                 )
             end for row in eachrow(dataframes[:highest_out])
         ]
diff --git a/src/constraints/ramping-and-unit-commitment.jl b/src/constraints/ramping-and-unit-commitment.jl
index bc545cea..48191ebe 100644
--- a/src/constraints/ramping-and-unit-commitment.jl
+++ b/src/constraints/ramping-and-unit-commitment.jl
@@ -1,7 +1,7 @@
 export add_ramping_and_unit_commitment_constraints!
 
 """
-    add_ramping_and_unit_commitment_constraints!(graph, ...)
+    add_ramping_and_unit_commitment_constraints!(model, graph, ...)
 
 Adds the ramping constraints for producer and conversion assets where ramping = true in assets_data
 """
@@ -12,6 +12,7 @@ function add_ramping_constraints!(
     df_units_on,
     df_highest_out,
     outgoing_flow_highest_out_resolution,
+    accumulated_units_lookup,
     accumulated_units,
     Ai,
     Auc,
@@ -54,7 +55,7 @@ function add_ramping_constraints!(
     model[:limit_units_on] = [
         @constraint(
             model,
-            row.units_on ≤ accumulated_units[row.year, row.asset],
+            row.units_on ≤ accumulated_units[accumulated_units_lookup[(row.asset, row.year)]],
             base_name = "limit_units_on[$(row.asset),$(row.year),$(row.rep_period),$(row.timesteps_block)]"
         ) for row in eachrow(df_units_on)
     ]
diff --git a/src/create-model.jl b/src/create-model.jl
index 35891902..b74fcdcc 100644
--- a/src/create-model.jl
+++ b/src/create-model.jl
@@ -1032,23 +1032,31 @@ function create_model(
                     @expression(model, 0.0)
                 end for (a, y, v) in accumulated_set_using_compact_method
             ]
-        @expression(
-            model,
-            accumulated_units[y ∈ Y, a ∈ A],
-            if a in decommissionable_assets_using_simple_method
-                accumulated_units_simple_method[y, a]
-            elseif a in decommissionable_assets_using_compact_method
-                sum(
-                    accumulated_units_compact_method[accumulated_set_using_compact_method_lookup[(
-                        a,
-                        y,
-                        v,
-                    )]] for v in V_all if (a, y, v) in accumulated_set_using_compact_method
-                )
-            else
-                sum(values(graph[a].initial_units[y]))
-            end
-        )
+
+        # Create a lookup set for accumulated units
+        accumulated_units_lookup =
+            Dict((a, y) => idx for (idx, (a, y)) in enumerate((aa, yy) for aa in A for yy in Y))
+
+        accumulated_units =
+            model[:accumulated_units] = JuMP.AffExpr[
+                if a in decommissionable_assets_using_simple_method
+                    @expression(model, accumulated_units_simple_method[y, a])
+                elseif a in decommissionable_assets_using_compact_method
+                    @expression(
+                        model,
+                        sum(
+                            accumulated_units_compact_method[accumulated_set_using_compact_method_lookup[(
+                                a,
+                                y,
+                                v,
+                            )]] for
+                            v in V_all if (a, y, v) in accumulated_set_using_compact_method
+                        )
+                    )
+                else
+                    @expression(model, sum(values(graph[a].initial_units[y])))
+                end for a in A for y in Y
+            ]
     end
 
     ## Expressions for the objective function
@@ -1133,6 +1141,7 @@ function create_model(
         decommissionable_assets_using_simple_method,
         decommissionable_assets_using_compact_method,
         V_all,
+        accumulated_units_lookup,
         accumulated_set_using_compact_method_lookup,
         Asb,
         assets_investment,
@@ -1223,6 +1232,7 @@ function create_model(
             df_units_on,
             dataframes[:highest_out],
             outgoing_flow_highest_out_resolution,
+            accumulated_units_lookup,
             accumulated_units,
             Ai,
             Auc,