diff --git a/.clang-tidy b/.clang-tidy
index 4772ac5a6..e9478297e 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -32,5 +32,7 @@ Checks: >
     performance-*,
     mpi-*,
     openmp-*'
+WarningsAsErrors: >-
+  performance-enum-size
 HeaderFilterRegex: 'palace/drivers|palace/fem|palace/linalg|palace/utils'
 FormatStyle: 'file'
diff --git a/palace/fem/coefficient.hpp b/palace/fem/coefficient.hpp
index 357b5c845..47975a32c 100644
--- a/palace/fem/coefficient.hpp
+++ b/palace/fem/coefficient.hpp
@@ -168,7 +168,7 @@ class BdrSurfaceCurrentVectorCoefficient : public mfem::VectorCoefficient,
 };
 
 // Helper for BdrSurfaceFluxCoefficient.
-enum class SurfaceFluxType
+enum class SurfaceFluxType : std::uint8_t
 {
   ELECTRIC,
   MAGNETIC,
@@ -292,7 +292,7 @@ inline void BdrSurfaceFluxCoefficient<SurfaceFluxType::POWER>::GetLocalFlux(
 }
 
 // Helper for InterfaceDielectricCoefficient.
-enum class InterfaceDielectricType
+enum class InterfaceDielectricType : std::uint8_t
 {
   DEFAULT,
   MA,
@@ -467,7 +467,7 @@ inline double InterfaceDielectricCoefficient<InterfaceDielectricType::SA>::Eval(
 }
 
 // Helper for EnergyDensityCoefficient.
-enum class EnergyDensityType
+enum class EnergyDensityType : std::uint8_t
 {
   ELECTRIC,
   MAGNETIC
diff --git a/palace/fem/libceed/integrator.hpp b/palace/fem/libceed/integrator.hpp
index 022b8b833..6d5a5fe2f 100644
--- a/palace/fem/libceed/integrator.hpp
+++ b/palace/fem/libceed/integrator.hpp
@@ -12,7 +12,7 @@ namespace palace::ceed
 {
 
 // Evaluation modes for CeedOperator fields for various integrators.
-enum EvalMode : unsigned int
+enum EvalMode : unsigned int  // NOLINT
 {
   Weight = 1 << 0,
   None = 1 << 1,
diff --git a/palace/linalg/eps.hpp b/palace/linalg/eps.hpp
index 835bac7cb..aa292e2f1 100644
--- a/palace/linalg/eps.hpp
+++ b/palace/linalg/eps.hpp
@@ -22,13 +22,13 @@ class DivFreeSolver;
 class EigenvalueSolver
 {
 public:
-  enum class ScaleType
+  enum class ScaleType : std::uint8_t
   {
     NONE,
     NORM_2
   };
 
-  enum class WhichType
+  enum class WhichType : std::uint8_t
   {
     LARGEST_MAGNITUDE,
     SMALLEST_MAGNITUDE,
@@ -41,7 +41,7 @@ class EigenvalueSolver
     TARGET_IMAGINARY
   };
 
-  enum class ErrorType
+  enum class ErrorType : std::uint8_t
   {
     ABSOLUTE,
     RELATIVE,
diff --git a/palace/linalg/iterative.hpp b/palace/linalg/iterative.hpp
index 84a1bfd4a..91ca0cee8 100644
--- a/palace/linalg/iterative.hpp
+++ b/palace/linalg/iterative.hpp
@@ -145,14 +145,14 @@ class CgSolver : public IterativeSolver<OperType>
 class GmresSolverBase
 {
 public:
-  enum class OrthogType
+  enum class OrthogType : std::uint8_t
   {
     MGS,
     CGS,
     CGS2
   };
 
-  enum class PrecSide
+  enum class PrecSide : std::uint8_t
   {
     LEFT,
     RIGHT
diff --git a/palace/linalg/slepc.hpp b/palace/linalg/slepc.hpp
index bd4fbc201..a63d26afc 100644
--- a/palace/linalg/slepc.hpp
+++ b/palace/linalg/slepc.hpp
@@ -52,7 +52,7 @@ PetscReal GetMaxSingularValue(MPI_Comm comm, const ComplexOperator &A, bool herm
 class SlepcEigenvalueSolver : public EigenvalueSolver
 {
 public:
-  enum class ProblemType
+  enum class ProblemType : std::uint8_t
   {
     HERMITIAN,
     NON_HERMITIAN,
@@ -63,7 +63,7 @@ class SlepcEigenvalueSolver : public EigenvalueSolver
     GYROSCOPIC
   };
 
-  enum class Type
+  enum class Type : std::uint8_t
   {
     KRYLOVSCHUR,
     POWER,
diff --git a/palace/models/waveportoperator.cpp b/palace/models/waveportoperator.cpp
index 250c5dd4d..6e4bed995 100644
--- a/palace/models/waveportoperator.cpp
+++ b/palace/models/waveportoperator.cpp
@@ -310,7 +310,7 @@ void Normalize(const GridFunction &S0t, GridFunction &E0t, GridFunction &E0n,
 }
 
 // Helper for BdrSubmeshEVectorCoefficient and BdrSubmeshHVectorCoefficient.
-enum class ValueType
+enum class ValueType : std::uint8_t
 {
   REAL,
   IMAG
diff --git a/palace/utils/configfile.hpp b/palace/utils/configfile.hpp
index 0014dc8ef..efa4e876b 100644
--- a/palace/utils/configfile.hpp
+++ b/palace/utils/configfile.hpp
@@ -76,7 +76,7 @@ struct ElementData
   std::array<double, 3> direction{{0.0, 0.0, 0.0}};
 
   // Coordinate system that the normal vector is expressed in.
-  enum class CoordinateSystem
+  enum class CoordinateSystem : std::uint8_t
   {
     CARTESIAN,
     CYLINDRICAL
@@ -93,7 +93,7 @@ struct ProblemData
 {
 public:
   // Simulation type.
-  enum class Type
+  enum class Type : std::uint8_t
   {
     DRIVEN,
     EIGENMODE,
@@ -444,7 +444,7 @@ struct WavePortData
   double d_offset = 0.0;
 
   // Eigenvalue solver type for boundary mode calculation.
-  enum class EigenSolverType
+  enum class EigenSolverType : std::uint8_t
   {
     DEFAULT,
     SLEPC,
@@ -486,7 +486,7 @@ struct SurfaceFluxData
 {
 public:
   // Surface flux type.
-  enum class Type
+  enum class Type : std::uint8_t
   {
     ELECTRIC,
     MAGNETIC,
@@ -519,7 +519,7 @@ struct InterfaceDielectricData
 {
 public:
   // Type of interface dielectric for computing electric field energy participation ratios.
-  enum class Type
+  enum class Type : std::uint8_t
   {
     DEFAULT,
     MA,
@@ -538,7 +538,7 @@ struct InterfaceDielectricData
   double tandelta = 0.0;
 
   // Side of internal boundaries on which to evaluate discontinuous field quantities.
-  enum class Side
+  enum class Side : std::uint8_t
   {
     SMALLER_REF_INDEX,
     LARGER_REF_INDEX
@@ -688,7 +688,7 @@ struct TransientSolverData
 {
 public:
   // Time integration scheme type.
-  enum class Type
+  enum class Type : std::uint8_t
   {
     DEFAULT,
     GEN_ALPHA,
@@ -698,7 +698,7 @@ struct TransientSolverData
   Type type = Type::DEFAULT;
 
   // Excitation type for port excitation.
-  enum class ExcitationType
+  enum class ExcitationType : std::uint8_t
   {
     SINUSOIDAL,
     GAUSSIAN,
@@ -729,7 +729,7 @@ struct LinearSolverData
 {
 public:
   // Solver type.
-  enum class Type
+  enum class Type : std::uint8_t
   {
     DEFAULT,
     AMS,
@@ -743,7 +743,7 @@ struct LinearSolverData
   Type type = Type::DEFAULT;
 
   // Krylov solver type.
-  enum class KspType
+  enum class KspType : std::uint8_t
   {
     DEFAULT,
     CG,
@@ -770,7 +770,7 @@ struct LinearSolverData
   int mg_max_levels = 100;
 
   // Type of coarsening for p-multigrid.
-  enum class MultigridCoarsenType
+  enum class MultigridCoarsenType : std::uint8_t
   {
     LINEAR,
     LOGARITHMIC
@@ -813,7 +813,7 @@ struct LinearSolverData
   int pc_mat_shifted = -1;
 
   // Choose left or right preconditioning.
-  enum class SideType
+  enum class SideType : std::uint8_t
   {
     DEFAULT,
     RIGHT,
@@ -823,7 +823,7 @@ struct LinearSolverData
 
   // Specify details for the column ordering method in the symbolic factorization for sparse
   // direct solvers.
-  enum class SymFactType
+  enum class SymFactType : std::uint8_t
   {
     DEFAULT,
     METIS,
@@ -838,7 +838,7 @@ struct LinearSolverData
 
   // Low-rank and butterfly compression parameters for sparse direct solvers which support
   // it (mainly STRUMPACK).
-  enum class CompressionType
+  enum class CompressionType : std::uint8_t
   {
     NONE,
     BLR,
@@ -885,7 +885,7 @@ struct LinearSolverData
 
   // Enable different variants of Gram-Schmidt orthogonalization for GMRES/FGMRES iterative
   // solvers and SLEPc eigenvalue solver.
-  enum class OrthogType
+  enum class OrthogType : std::uint8_t
   {
     MGS,
     CGS,
@@ -913,7 +913,7 @@ struct SolverData
   int q_order_extra = 0;
 
   // Device used to configure MFEM.
-  enum class Device
+  enum class Device : std::uint8_t
   {
     CPU,
     GPU,
diff --git a/palace/utils/iodata.hpp b/palace/utils/iodata.hpp
index b57d3082f..bbf7eb87c 100644
--- a/palace/utils/iodata.hpp
+++ b/palace/utils/iodata.hpp
@@ -51,7 +51,7 @@ class IoData
   // Redimensionalize values for output. Outputs which depend on the fields assume a
   // characteristic reference magnetic field strength Hc such that Pc = 1 W, where Pc is the
   // characteristic reference power.
-  enum class ValueType
+  enum class ValueType :  std::uint8_t
   {
     TIME,          // [ns]
     FREQUENCY,     // [GHz]
diff --git a/palace/utils/timer.hpp b/palace/utils/timer.hpp
index f4cd9fa5f..e674cbf0e 100644
--- a/palace/utils/timer.hpp
+++ b/palace/utils/timer.hpp
@@ -24,7 +24,7 @@ class Timer
   using Duration = std::chrono::duration<double>;
   using TimePoint = typename Clock::time_point;
 
-  enum Index
+  enum Index : std::uint8_t
   {
     INIT = 0,
     CONSTRUCT,            // Space and operator construction