diff --git a/activestorage/active.py b/activestorage/active.py
index 00d5d09d..b0db0912 100644
--- a/activestorage/active.py
+++ b/activestorage/active.py
@@ -1,8 +1,12 @@
 import os
 import numpy as np
+import yaml
+
+import activestorage
 
 #FIXME: Consider using h5py throughout, for more generality
 from netCDF4 import Dataset
+from pathlib import Path
 from zarr.indexing import (
     OrthogonalIndexer,
 )
@@ -10,6 +14,37 @@
 from activestorage import netcdf_to_zarr as nz
 
 
+def _read_config_file(storage_type):
+    """Read config user file and store settings in a dictionary."""
+    base_path = Path(activestorage.__file__).parent
+    if storage_type == "S3":
+        config_file = base_path / Path("config-s3-storage.yml")
+    elif storage_type == "Posix":
+        config_file = base_path / Path("config-Posix-storage.yml")
+    else:
+        raise ValueError(f"Storage type {storage_type} not known.")
+    # should not need this if conf file is at package-level
+    # if not config_file.exists():
+    #     raise IOError(f'Config file `{config_file}` does not exist.')
+
+    with open(config_file, 'r') as file:
+        cfg = yaml.safe_load(file)
+
+    return cfg
+
+
+def _extract_method(method):
+   """Extract functional method from string. Works like eval but more secure."""
+   if method.split(".")[0] == "np" or method.split(".")[0] == "numpy":
+       try:
+           func = getattr(np, method.split(".")[1])
+           return func
+       except AttributeError:
+           raise AttributeError(f"Method {method} is not a valid Numpy method.")
+   else:
+       raise ValueError(f"Could not recognize method {method} as permitted.")
+
+
 class Active:
     """ 
     Instantiates an interface to active storage which contains either zarr files
@@ -21,20 +56,9 @@ class Active:
     Version 2 will add methods for actual active storage.
 
     """
-    def __new__(cls, *args, **kwargs):
-        """Store reduction methods."""
-        instance = super().__new__(cls)
-        instance._methods = {
-            "min": np.min,
-            "max": np.max,
-            "sum": np.sum,
-            # For the unweighted mean we calulate the sum and divide
-            # by the number of non-missing elements
-            "mean": np.sum,
-        }
-        return instance
-
-    def __init__(self, uri, ncvar, missing_value=None, fill_value=None, valid_min=None, valid_max=None):
+    def __init__(self, uri, ncvar, storage_type="Posix",
+                 missing_value=None, fill_value=None,
+                 valid_min=None, valid_max=None):
         """
         Instantiate with a NetCDF4 dataset and the variable of interest within that file.
         (We need the variable, because we need variable specific metadata from within that
@@ -52,7 +76,18 @@ def __init__(self, uri, ncvar, missing_value=None, fill_value=None, valid_min=No
             raise ValueError("Must set a netCDF variable name to slice")
         self.zds = None
 
-        self._version = 1
+        # storage type
+        self.storage_type = storage_type
+
+        # read config file
+        self._config = _read_config_file(self.storage_type)
+
+        # read methods version, components
+        self._version = self._config.get("version", 1)
+        self._methods = self._config.get("methods", None)
+        # should not need this if conf file is at package-level
+        # if not self._methods:
+        #     raise ValueError(f"Configuration dict {self._config} needs a valid methods group.")
         self._components = False
         self._method = None
        
@@ -148,13 +183,14 @@ def method(self):
         ==========  ==================================================
 
         """
-        return self._methods.get(self._method)
+        method = self._methods.get(self._method, None)
+        if method:
+            return _extract_method(method)
 
     @method.setter
     def method(self, value):
         if value is not None and value not in self._methods:
             raise ValueError(f"Bad 'method': {value}. Choose from min/max/mean/sum.")
-
         self._method = value
 
     @property
diff --git a/activestorage/config-Posix-storage.yml b/activestorage/config-Posix-storage.yml
new file mode 100644
index 00000000..ccfaa808
--- /dev/null
+++ b/activestorage/config-Posix-storage.yml
@@ -0,0 +1,6 @@
+version: 1
+methods:
+  min: np.min
+  max: np.max
+  sum: np.sum
+  mean: np.sum
diff --git a/activestorage/config-s3-storage.yml b/activestorage/config-s3-storage.yml
new file mode 100644
index 00000000..3bb535b0
--- /dev/null
+++ b/activestorage/config-s3-storage.yml
@@ -0,0 +1,6 @@
+version: 1
+methods:
+  min: min
+  max: max
+  sum: dimsum
+  mean: mean
diff --git a/tests/test_package.py b/tests/test_package.py
index 3ee2f41c..51834a5c 100644
--- a/tests/test_package.py
+++ b/tests/test_package.py
@@ -1,6 +1,7 @@
 import activestorage
 
 from activestorage import Active as act
+from activestorage.active import _read_config_file as read_conf
 
 
 # test version
@@ -29,3 +30,19 @@ def test_active_class_attrs():
     assert hasattr(act, "components")
     assert hasattr(act, "method")
     assert hasattr(act, "ncvar")
+
+
+# check validity of conf files
+def test_read_config_file():
+    """Test validity of package-level files."""
+    posix_mandatory_keys = ["version", "methods"]
+    s3_mandatory_keys = ["version", "methods"]
+    posix_file = read_conf("Posix")
+    s3_file = read_conf("S3")
+    print(posix_file)
+    print(s3_file)
+    for mandatory_key in posix_mandatory_keys:
+        assert mandatory_key in posix_file
+    for mandatory_key in s3_mandatory_keys:
+        assert mandatory_key in s3_file
+    
diff --git a/tests/unit/test_active.py b/tests/unit/test_active.py
index 5de297e1..a47caee2 100644
--- a/tests/unit/test_active.py
+++ b/tests/unit/test_active.py
@@ -83,3 +83,56 @@ def test_active():
     init = active.__init__(uri=uri, ncvar=ncvar, missing_value=True,
                            fill_value=1e20, valid_min=-1,
                            valid_max=1200)
+
+
+def test_config_s3():
+    uri = "tests/test_data/cesm2_native.nc"
+    ncvar = "TREFHT"
+    active = Active(uri, ncvar=ncvar, storage_type="S3")
+    assert active._methods == {'max': 'max', 'mean': 'mean',
+                               'min': 'min', 'sum': 'dimsum'}
+    assert active.method is None
+    assert active._version == 1
+
+    active._version = 2
+
+    # statistical method can not be executed
+    active.method = "mean"
+    with pytest.raises(ValueError) as exc:
+        active[:]
+    assert str(exc.value) == "Could not recognize method mean as permitted."
+
+    # bad name for statistical method
+    with pytest.raises(ValueError) as exc:
+        active.method = "meany"
+    assert str(exc.value) == "Bad 'method': meany. Choose from min/max/mean/sum."
+
+
+def test_config_Posix():
+    uri = "tests/test_data/cesm2_native.nc"
+    ncvar = "TREFHT"
+    active = Active(uri, ncvar=ncvar, storage_type="Posix")
+    assert active._methods == {'max': 'np.max', 'mean': 'np.sum',
+                               'min': 'np.min', 'sum': 'np.sum'}
+    assert active.method is None
+    assert active._version == 1
+
+    active._version = 2
+
+    # usual run
+    active.method = "mean"  # will exec np.mean from config
+    assert active[:] == 284.22694905598956
+
+    # passing wrong numpy method
+    active._methods["mean"] = "np.meany"
+    with pytest.raises(AttributeError) as exc:
+        active[:]
+    assert str(exc.value) == "Method np.meany is not a valid Numpy method."
+
+
+def test_config_invalid_storage_type():
+    uri = "tests/test_data/cesm2_native.nc"
+    ncvar = "TREFHT"
+    with pytest.raises(ValueError) as exc:
+        Active(uri, ncvar=ncvar, storage_type="cowabunga")
+    assert str(exc.value) == "Storage type cowabunga not known."