Adds support for fixed fees charged per billing period

Author: johnmckibbin

tariffs/tariff.py

@@ -221,6 +221,8 @@ def charge_types(self):
                 charge_types.add('consumption')
             if charge.type == 'generation':
                 charge_types.add('generation')
+            if charge.type == 'fixed':
+                charge_types.add('fixed')
 
         return list(charge_types)
 
@@ -350,6 +352,12 @@ def apply(self, meter_data, start=None, end=None):
             peak_monthly = demand_data.resample(PERIOD_TO_TIMESTEP[self.billing_period]).max()
             cost_items.update(self.apply_by_charge_type(peak_monthly, cost_items, 'demand'))
 
+        if 'fixed' in self.charge_types:
+            billing_periods = len(meter_data.resample(PERIOD_TO_TIMESTEP[self.billing_period]).mean())
+            for charge in self.charges:
+                if charge.type == 'fixed':
+                    cost_items[charge.name]['cost'] = billing_periods * charge.rate
+
         # Transform the output data into the specified output format
         cost_dict = {
             'name': self.name,

tests/test_calculations.py

@@ -23,6 +23,12 @@ def tariff_file(self):
             tariff = json_codec.load(f, Tariff)
         return tariff
 
+    @pytest.fixture
+    def fixed_tariff(self):
+        with open('./fixtures/fixed_tariff.json') as f:
+            tariff = json_codec.load(f, Tariff)
+        return tariff
+
     @pytest.fixture
     def block_tariff(self):
         with open('./fixtures/block_tariff.json') as f:
@@ -59,6 +65,11 @@ def demand_tariff(self):
             tariff = json_codec.load(f, Tariff)
         return tariff
 
+    def test_fixed_tariff(self, fixed_tariff, meter_data):
+        expected_bill = 12.0
+        actual_bill = fixed_tariff.apply(meter_data)
+        assert actual_bill.cost == expected_bill
+
     def test_block_tariff(self, block_tariff, meter_data):
         expected_bill = 35040.0
         actual_bill = block_tariff.apply(meter_data)