diff --git a/opm/autodiff/Compat.cpp b/opm/autodiff/Compat.cpp
index 2b9d8c00b..2ff209b7c 100644
--- a/opm/autodiff/Compat.cpp
+++ b/opm/autodiff/Compat.cpp
@@ -75,10 +75,18 @@ std::vector< double >& stripe( const std::vector< double >& v,
 
 
 data::Solution simToSolution( const SimulationDataContainer& reservoir,
+                              const bool use_si_units,
                               PhaseUsage phases ) {
+
+    // Set up unit system to use to suppress conversion if use_si_units is true.
+    const UnitSystem::measure press_unit = use_si_units ? UnitSystem::measure::identity : UnitSystem::measure::pressure;
+    const UnitSystem::measure temp_unit = use_si_units ? UnitSystem::measure::identity : UnitSystem::measure::temperature;
+    const UnitSystem::measure rs_unit = use_si_units ? UnitSystem::measure::identity : UnitSystem::measure::gas_oil_ratio;
+    const UnitSystem::measure rv_unit = use_si_units ? UnitSystem::measure::identity : UnitSystem::measure::oil_gas_ratio;
+
     data::Solution sol;
-    sol.insert( "PRESSURE", UnitSystem::measure::pressure, reservoir.pressure() , data::TargetType::RESTART_SOLUTION);
-    sol.insert( "TEMP"    , UnitSystem::measure::temperature, reservoir.temperature() , data::TargetType::RESTART_SOLUTION );
+    sol.insert( "PRESSURE", press_unit, reservoir.pressure() , data::TargetType::RESTART_SOLUTION);
+    sol.insert( "TEMP"    , temp_unit, reservoir.temperature() , data::TargetType::RESTART_SOLUTION );
 
     const auto ph = reservoir.numPhases();
     const auto& sat = reservoir.saturation();
@@ -95,11 +103,11 @@ data::Solution simToSolution( const SimulationDataContainer& reservoir,
     }
 
     if( reservoir.hasCellData( BlackoilState::GASOILRATIO ) ) {
-        sol.insert( "RS", UnitSystem::measure::gas_oil_ratio, reservoir.getCellData( BlackoilState::GASOILRATIO ) , data::TargetType::RESTART_SOLUTION );
+        sol.insert( "RS", rs_unit, reservoir.getCellData( BlackoilState::GASOILRATIO ) , data::TargetType::RESTART_SOLUTION );
     }
 
     if( reservoir.hasCellData( BlackoilState::RV ) ) {
-        sol.insert( "RV", UnitSystem::measure::oil_gas_ratio, reservoir.getCellData( BlackoilState::RV ) , data::TargetType::RESTART_SOLUTION );
+        sol.insert( "RV", rv_unit, reservoir.getCellData( BlackoilState::RV ) , data::TargetType::RESTART_SOLUTION );
     }
 
     if (reservoir.hasCellData( BlackoilSolventState::SSOL)) {
diff --git a/opm/autodiff/Compat.hpp b/opm/autodiff/Compat.hpp
index 76ee2d033..705385911 100644
--- a/opm/autodiff/Compat.hpp
+++ b/opm/autodiff/Compat.hpp
@@ -51,7 +51,10 @@ namespace Opm {
     /// Returns Solution with the following fields:
     ///   PRESSURE, TEMP (unconditionally)
     ///   SWAT, SGAS, RS, RV, SSOL (if appropriate fields present in input)
+    /// If use_si_units is true, the fields will have the measure UnitSystem::measure::identity,
+    /// and therefore *not* be converted to customary units (depending on family) upon output.
     data::Solution simToSolution( const SimulationDataContainer& reservoir,
+                                  const bool use_si_units,
                                   PhaseUsage phases );
 
     /// Copies the following fields from sol into state (all conditionally):
diff --git a/opm/autodiff/SimulatorFullyImplicitBlackoilOutput.cpp b/opm/autodiff/SimulatorFullyImplicitBlackoilOutput.cpp
index 5899e88d3..4503ec0cf 100644
--- a/opm/autodiff/SimulatorFullyImplicitBlackoilOutput.cpp
+++ b/opm/autodiff/SimulatorFullyImplicitBlackoilOutput.cpp
@@ -243,7 +243,7 @@ namespace Opm
         data::Solution localCellData{};
         if( output_ )
         {
-            localCellData = simToSolution(localState, phaseUsage_); // Get "normal" data (SWAT, PRESSURE, ...);
+            localCellData = simToSolution(localState, restart_double_si_, phaseUsage_); // Get "normal" data (SWAT, PRESSURE, ...);
         }
         writeTimeStepWithCellProperties(timer, localState, localCellData ,
                                         localWellState, substep);
@@ -348,7 +348,8 @@ namespace Opm
                                       substep,
                                       timer.simulationTimeElapsed(),
                                       simProps,
-                                      wellState.report(phaseUsage_));
+                                      wellState.report(phaseUsage_),
+                                      restart_double_si_);
             }
         }
 
diff --git a/opm/autodiff/SimulatorFullyImplicitBlackoilOutput.hpp b/opm/autodiff/SimulatorFullyImplicitBlackoilOutput.hpp
index ad6e070d1..63d67ecdd 100644
--- a/opm/autodiff/SimulatorFullyImplicitBlackoilOutput.hpp
+++ b/opm/autodiff/SimulatorFullyImplicitBlackoilOutput.hpp
@@ -307,6 +307,7 @@ namespace Opm
         // Parameters for output.
         const std::string outputDir_;
         const int output_interval_;
+        const bool restart_double_si_;
 
         int lastBackupReportStep_;
 
@@ -338,6 +339,7 @@ namespace Opm
         parallelOutput_( output_ ? new ParallelDebugOutput< Grid >( grid, eclipseState, phaseUsage.num_phases, phaseUsage ) : 0 ),
         outputDir_( output_ ? param.getDefault("output_dir", std::string("output")) : "." ),
         output_interval_( output_ ? param.getDefault("output_interval", 1): 0 ),
+        restart_double_si_( output_ ? param.getDefault("restart_double_si", false) : false ),
         lastBackupReportStep_( -1 ),
         phaseUsage_( phaseUsage ),
         eclipseState_(eclipseState),
@@ -415,13 +417,20 @@ namespace Opm
                          ExtraData& extra )
     {
         std::map<std::string, UnitSystem::measure> solution_keys {{"PRESSURE" , UnitSystem::measure::pressure},
-                                                                  {"SWAT" , UnitSystem::measure::identity},
-                                                                  {"SGAS" , UnitSystem::measure::identity},
-                                                                  {"TEMP" , UnitSystem::measure::temperature},
-                                                                  {"RS" , UnitSystem::measure::gas_oil_ratio},
-                                                                  {"RV" , UnitSystem::measure::oil_gas_ratio},
+                                                                  {"SWAT"     , UnitSystem::measure::identity},
+                                                                  {"SGAS"     , UnitSystem::measure::identity},
+                                                                  {"TEMP"     , UnitSystem::measure::temperature},
+                                                                  {"RS"       , UnitSystem::measure::gas_oil_ratio},
+                                                                  {"RV"       , UnitSystem::measure::oil_gas_ratio},
                                                                   {"OPMEXTRA" , UnitSystem::measure::identity}};
 
+        if (restart_double_si_) {
+            // Avoid any unit conversions, treat restart input as SI units.
+            for (auto& elem : solution_keys) {
+                elem.second = UnitSystem::measure::identity;
+            }
+        }
+
         // gives a dummy dynamic_list_econ_limited
         DynamicListEconLimited dummy_list_econ_limited;
         WellsManager wellsmanager(eclipseState_,
@@ -936,7 +945,7 @@ namespace Opm
                 SimulationDataContainer sd =
                     detail::convertToSimulationDataContainer( physicalModel.getSimulatorData(), localState, phaseUsage_ );
 
-                localCellData = simToSolution( sd, phaseUsage_); // Get "normal" data (SWAT, PRESSURE, ...);
+                localCellData = simToSolution( sd, restart_double_si_, phaseUsage_); // Get "normal" data (SWAT, PRESSURE, ...);
 
                 detail::getRestartData( localCellData, std::move(sd), phaseUsage_, physicalModel,
                                         restartConfig, reportStepNum, logMessages );