Add class for representing Energy quantities

Signed-off-by: Sahas Subramanian <[email protected]>

Author: shsms

src/frequenz/sdk/timeseries/_quantities.py

@@ -466,3 +466,74 @@ def as_kilovolts(self) -> float:
             The voltage in kilovolts.
         """
         return self._base_value / 1e3
+
+
+class Energy(
+    Quantity,
+    exponent_unit_map={
+        0: "Wh",
+        3: "kWh",
+        6: "MWh",
+    },
+):
+    """An energy quantity."""
+
+    @classmethod
+    def from_watt_hours(cls, watt_hours: float) -> Self:
+        """Initialize a new energy quantity.
+
+        Args:
+            watt_hours: The energy in watt hours.
+
+        Returns:
+            A new energy quantity.
+        """
+        return cls(value=watt_hours, exponent=0)
+
+    @classmethod
+    def from_kilowatt_hours(cls, kilowatt_hours: float) -> Self:
+        """Initialize a new energy quantity.
+
+        Args:
+            kilowatt_hours: The energy in kilowatt hours.
+
+        Returns:
+            A new energy quantity.
+        """
+        return cls(value=kilowatt_hours, exponent=3)
+
+    @classmethod
+    def from_megawatt_hours(cls, megawatt_hours: float) -> Self:
+        """Initialize a new energy quantity.
+
+        Args:
+            megawatt_hours: The energy in megawatt hours.
+
+        Returns:
+            A new energy quantity.
+        """
+        return cls(value=megawatt_hours, exponent=6)
+
+    def as_watt_hours(self) -> float:
+        """Return the energy in watt hours.
+
+        Returns:
+            The energy in watt hours.
+        """
+        return self._base_value
+
+    def as_kilowatt_hours(self) -> float:
+        """Return the energy in kilowatt hours.
+
+        Returns:
+            The energy in kilowatt hours.
+        """
+        return self._base_value / 1e3
+
+    def as_megawatt_hours(self) -> float:
+        """Return the energy in megawatt hours.
+
+        Returns:
+            The energy in megawatt hours.
+        """
+        return self._base_value / 1e6

tests/timeseries/test_quantities.py

@@ -5,7 +5,13 @@
 
 import pytest
 
-from frequenz.sdk.timeseries._quantities import Current, Power, Quantity, Voltage
+from frequenz.sdk.timeseries._quantities import (
+    Current,
+    Energy,
+    Power,
+    Quantity,
+    Voltage,
+)
 
 
 class Fz1(
@@ -193,3 +199,19 @@ def test_voltage() -> None:
     assert voltage == Voltage.from_kilovolts(0.006)
     assert voltage == Voltage.from_volts(6.0)
     assert voltage != Voltage.from_volts(5.0)
+
+
+def test_energy() -> None:
+    """Test the energy class."""
+    energy = Energy.from_watt_hours(0.0000002)
+    assert f"{energy:.9}" == "0.0000002 Wh"
+    energy = Energy.from_megawatt_hours(600000.0)
+    assert f"{energy}" == "600000 MWh"
+
+    energy = Energy.from_kilowatt_hours(6.0)
+    assert energy.as_watt_hours() == 6000.0
+    assert energy.as_kilowatt_hours() == 6.0
+    assert energy.as_megawatt_hours() == 0.006
+    assert energy == Energy.from_megawatt_hours(0.006)
+    assert energy == Energy.from_kilowatt_hours(6.0)
+    assert energy != Energy.from_kilowatt_hours(5.0)