diff --git a/lib/spack/spack/cmd/solve.py b/lib/spack/spack/cmd/solve.py
index 64219b300f..e81161de90 100644
--- a/lib/spack/spack/cmd/solve.py
+++ b/lib/spack/spack/cmd/solve.py
@@ -10,6 +10,7 @@
 import sys
 
 import llnl.util.tty as tty
+import llnl.util.tty.color as color
 
 import spack
 import spack.cmd
@@ -23,15 +24,20 @@
 level = 'long'
 
 #: output options
-show_options = ('asp', 'output', 'solutions')
+show_options = ('asp', 'opt', 'output', 'solutions')
 
 
 def setup_parser(subparser):
     # Solver arguments
     subparser.add_argument(
-        '--show', action='store', default=('solutions'),
-        help="outputs: a list with any of: "
-        "%s (default), all" % ', '.join(show_options))
+        '--show', action='store', default='opt,solutions',
+        help="select outputs: comma-separated list of: \n"
+        "  asp          asp program text\n"
+        "  opt          optimization criteria for best model\n"
+        "  output       raw clingo output\n"
+        "  solutions    models found by asp program\n"
+        "  all          all of the above"
+    )
     subparser.add_argument(
         '--models', action='store', type=int, default=0,
         help="number of solutions to search (default 0 for all)")
@@ -41,10 +47,10 @@ def setup_parser(subparser):
         subparser, ['long', 'very_long', 'install_status'])
     subparser.add_argument(
         '-y', '--yaml', action='store_const', dest='format', default=None,
-        const='yaml', help='print concrete spec as YAML')
+        const='yaml', help='print concrete spec as yaml')
     subparser.add_argument(
         '-j', '--json', action='store_const', dest='format', default=None,
-        const='json', help='print concrete spec as YAML')
+        const='json', help='print concrete spec as json')
     subparser.add_argument(
         '-c', '--cover', action='store',
         default='nodes', choices=['nodes', 'edges', 'paths'],
@@ -113,9 +119,18 @@ def solve(parser, args):
         best = min(result.answers)
 
         opt, _, answer = best
-        if not args.format:
-            tty.msg("Best of %d answers." % result.nmodels)
-            tty.msg("Optimization: %s" % opt)
+        if ("opt" in dump) and (not args.format):
+            tty.msg("Best of %d considered solutions." % result.nmodels)
+            tty.msg("Optimization Criteria:")
+
+            maxlen = max(len(s) for s in result.criteria)
+            color.cprint(
+                "@*{  Priority  Criterion %sValue}" % ((maxlen - 10) * " ")
+            )
+            for i, (name, val) in enumerate(zip(result.criteria, opt)):
+                fmt = "  @K{%%-8d}  %%-%ds%%5d" % maxlen
+                color.cprint(fmt % (i + 1, name, val))
+            print()
 
         # iterate over roots from command line
         for input_spec in specs:
diff --git a/lib/spack/spack/solver/asp.py b/lib/spack/spack/solver/asp.py
index 179dff2052..712a21b05b 100644
--- a/lib/spack/spack/solver/asp.py
+++ b/lib/spack/spack/solver/asp.py
@@ -207,6 +207,9 @@ def __init__(self, asp=None):
         self.answers = []
         self.cores = []
 
+        # names of optimization criteria
+        self.criteria = []
+
     def print_cores(self):
         for core in self.cores:
             tty.msg(
@@ -354,6 +357,7 @@ def stringify(x):
                 return x.string or str(x)
 
         if result.satisfiable:
+            # build spec from the best model
             builder = SpecBuilder(specs)
             min_cost, best_model = min(models)
             tuples = [
@@ -361,8 +365,20 @@ def stringify(x):
                 for sym in best_model
             ]
             answers = builder.build_specs(tuples)
+
+            # add best spec to the results
             result.answers.append((list(min_cost), 0, answers))
 
+            # pull optimization criteria names out of the solution
+            criteria = [
+                (int(args[0]), args[1]) for name, args in tuples
+                if name == "opt_criterion"
+            ]
+            result.criteria = [t[1] for t in sorted(criteria, reverse=True)]
+
+            # record the number of models the solver considered
+            result.nmodels = len(models)
+
         elif cores:
             symbols = dict(
                 (a.literal, a.symbol)
diff --git a/lib/spack/spack/solver/concretize.lp b/lib/spack/spack/solver/concretize.lp
index cbde0076fb..898927a8a8 100644
--- a/lib/spack/spack/solver/concretize.lp
+++ b/lib/spack/spack/solver/concretize.lp
@@ -705,19 +705,31 @@ no_flags(Package, FlagType)
 %-----------------------------------------------------------------------------
 % How to optimize the spec (high to low priority)
 %-----------------------------------------------------------------------------
+% Each criterion below has:
+%   1. an opt_criterion(ID, Name) fact that describes the criterion, and
+%   2. a `#minimize{ 0@2 : #true }.` statement that ensures the criterion
+%      is displayed (clingo doesn't display sums over empty sets by default)
 
 % The highest priority is to minimize the:
 % 1. Version weight
 % 2. Number of variants with a non default value, if not set
 % for the root(Package)
-#minimize { Weight@15 : root(Package),version_weight(Package, Weight)}.
+opt_criterion(15, "version weight").
+#minimize{ 0@15 : #true }.
+#minimize { Weight@15 : root(Package),version_weight(Package, Weight) }.
+
+opt_criterion(14, "number of non-default variants (roots)").
+#minimize{ 0@14 : #true }.
 #minimize {
     Weight@14,Package,Variant,Value
     : variant_not_default(Package, Variant, Value, Weight), root(Package)
 }.
+
 % If the value is a multivalued variant there could be multiple
 % values set as default. Since a default value has a weight of 0 we
 % need to maximize their number below to ensure they're all set
+opt_criterion(13, "multi-valued variants + preferred providers for roots").
+#minimize{ 0@13 : #true }.
 #maximize {
     1@13,Package,Variant,Value
     : variant_not_default(Package, Variant, Value, Weight),
@@ -730,19 +742,27 @@ no_flags(Package, FlagType)
 }.
 
 % Try to use default variants or variants that have been set
+opt_criterion(11, "number of non-default variants (non-roots)").
+#minimize{ 0@11 : #true }.
 #minimize {
     Weight@11,Package,Variant,Value
     : variant_not_default(Package, Variant, Value, Weight), not root(Package)
 }.
+
 % Minimize the weights of the providers, i.e. use as much as
 % possible the most preferred providers
+opt_criterion(9, "number of non-default providers (non-roots)").
+#minimize{ 0@9 : #true }.
 #minimize{
     Weight@9,Provider
     : provider_weight(Provider, Weight), not root(Provider)
 }.
+
 % If the value is a multivalued variant there could be multiple
 % values set as default. Since a default value has a weight of 0 we
 % need to maximize their number below to ensure they're all set
+opt_criterion(8, "count of non-root multi-valued variants").
+#minimize{ 0@8 : #true }.
 #maximize {
     1@8,Package,Variant,Value
     : variant_not_default(Package, Variant, Value, Weight),
@@ -754,18 +774,29 @@ no_flags(Package, FlagType)
 % while minimizing the number of nodes. This is done because
 % a maximization on the number of matches for compilers is highly
 % correlated to a preference to have as many nodes as possible
+opt_criterion(7, "compiler matches + number of nodes").
+#minimize{ 0@7 : #true }.
 #minimize{ 1@7,Package : node(Package) }.
 #maximize{ Weight@7,Package : compiler_version_match(Package, Weight) }.
 
 % Choose more recent versions for nodes
+opt_criterion(6, "version badness").
+#minimize{ 0@6 : #true }.
 #minimize{
     Weight@6,Package : version_weight(Package, Weight)
 }.
 
 % Try to use preferred compilers
+opt_criterion(5, "non-preferred compilers").
+#minimize{ 0@5 : #true }.
 #minimize{ Weight@5,Package : compiler_weight(Package, Weight) }.
 
 % Maximize the number of matches for targets in the DAG, try
 % to select the preferred target.
+opt_criterion(4, "target matches").
+#minimize{ 0@4 : #true }.
 #maximize{ Weight@4,Package : node_target_match(Package, Weight) }.
+
+opt_criterion(3, "non-preferred targets").
+#minimize{ 0@3 : #true }.
 #minimize{ Weight@3,Package : node_target_weight(Package, Weight) }.
diff --git a/lib/spack/spack/solver/display.lp b/lib/spack/spack/solver/display.lp
index f67c4b6c3c..c1231ca62a 100644
--- a/lib/spack/spack/solver/display.lp
+++ b/lib/spack/spack/solver/display.lp
@@ -8,6 +8,9 @@
 %
 % This section determines what parts of the model are printed at the end
 %==============================================================================
+
+% Spec-related functions.
+% Used to build the result of the solve.
 #show node/1.
 #show depends_on/3.
 #show version/2.
@@ -21,12 +24,7 @@
 #show node_flag_compiler_default/1.
 #show node_flag_source/2.
 #show no_flags/2.
-
-#show variant_not_default/4.
-#show provider_weight/2.
-#show version_weight/2.
-#show compiler_version_match/2.
-#show compiler_weight/2.
-#show node_target_match/2.
-#show node_target_weight/2.
 #show external_spec_selected/2.
+
+% names of optimization criteria
+#show opt_criterion/2.