diff --git a/db/migrate/20250509123551_update_solarthermal_buildings.rb b/db/migrate/20250509123551_update_solarthermal_buildings.rb
new file mode 100644
index 000000000..5a6b23077
--- /dev/null
+++ b/db/migrate/20250509123551_update_solarthermal_buildings.rb
@@ -0,0 +1,49 @@
+require 'etengine/scenario_migration'
+
+class UpdateSolarthermalBuildings < ActiveRecord::Migration[7.1]
+  include ETEngine::ScenarioMigration
+
+  def up
+    migrate_scenarios do |scenario|
+      # Insert your code here which will migrate each scenario, and delete this
+      # documentation comment.
+      #
+
+      if scenario.user_values.key?('buildings_space_heater_solar_thermal_share')
+        scenario.user_values['buildings_space_heater_solar_thermal_share'] *= 0.13
+      end
+      #
+      # If you need to reference data from Atlas, be sure to check that the
+      # dataset used by the scenario still exists:
+      #
+      #   next unless Atlas::Dataset.exists?(scenario.area_code)
+      #
+      # Scenarios will be automatically saved if changes were made.
+      #
+      # ### Candidate scenarios
+      #
+      # By default, all `keep_updated` scenarios are migrated, along with any
+      # other scenarios modified in the last month. You may supply a
+      # custom cutoff date for migrating unprotected scenarios with the `since`
+      # keyword argument.
+      #
+      # For example, to migrate scenarios up to three months old whose
+      # `keep_updated` attribute is false:
+      #
+      #   migrate_scenarios(since: 3.months.ago) do |scenario|
+      #     # ...
+      #   end
+      #
+      # ### Errors
+      #
+      # An error will be raised if no scenarios were migrated, as it is often
+      # unexpected for a migration to result in no changes. If you wish to
+      # disable this behaviour, supply `raise_on_no_changes: false` to
+      # `migrate_scenarios`. For example:
+      #
+      #   migrate_scenarios(raise_on_no_changes: false) do |scenario|
+      #     # ...
+      #   end
+    end
+  end
+end