diff --git a/spinn_machine/version/version_3.py b/spinn_machine/version/version_3.py
index b8dc36e4..3c5c83a2 100644
--- a/spinn_machine/version/version_3.py
+++ b/spinn_machine/version/version_3.py
@@ -102,9 +102,10 @@ def get_idle_energy(
             raise SpinnMachineException(
                 "A version 3 SpiNNaker 1 board has exactly one board!")
 
-        # We allow n_boards to be 0 to discount the cost of the board,
-        # so we multiply by n_boards in case it is 0!
-        return n_boards * self.WATTS_FOR_4_CHIP_BOARD_IDLE_COST * time_s
+        # We allow n_boards to be 0 to discount the cost of the board
+        if n_boards == 0:
+            return n_chips * self.WATTS_PER_IDLE_CHIP * time_s
+        return self.WATTS_FOR_4_CHIP_BOARD_IDLE_COST * time_s
 
     @overrides(VersionSpin1.get_active_energy)
     def get_active_energy(
diff --git a/spinn_machine/version/version_5.py b/spinn_machine/version/version_5.py
index 92dc2b29..94da5303 100644
--- a/spinn_machine/version/version_5.py
+++ b/spinn_machine/version/version_5.py
@@ -112,8 +112,11 @@ def get_idle_energy(
             self, time_s: float, n_frames: int, n_boards: int,
             n_chips: int) -> float:
 
-        # The board idle energy
-        energy = n_boards * self.WATTS_FOR_48_CHIP_BOARD_IDLE_COST * time_s
+        # We allow n_boards to be 0 to discount the cost of the board
+        if n_boards == 0:
+            energy = n_chips * self.WATTS_PER_IDLE_CHIP * time_s
+        else:
+            energy = n_boards * self.WATTS_FOR_48_CHIP_BOARD_IDLE_COST * time_s
 
         # The container of the boards idle energy
         if n_frames != 0:
diff --git a/spinn_machine/version/version_spin1.py b/spinn_machine/version/version_spin1.py
index 6cc1d362..53566bac 100644
--- a/spinn_machine/version/version_spin1.py
+++ b/spinn_machine/version/version_spin1.py
@@ -28,6 +28,11 @@ class VersionSpin1(AbstractVersion, metaclass=AbstractBase):
     Shared code for all Spin1 board versions
     """
 
+    #: From Optimising the overall power usage on the SpiNNaker neuromimetic
+    #: platform - all chips on a 48-chip board together use 5.23 + 5.17 + 5.52W
+    #: + SDRAM of 0.90W = 16.82W when idle, so each chip use 0.35W
+    WATTS_PER_IDLE_CHIP: Final = 0.35
+
     #: From measuring the power of all 48 chips on a boxed board with all cores
     #: idle for 1 hour and 806 cores active for 1 hour we get 31.88W idle and
     #: 59.38W active, so 27.50W active overhead, which is 0.034W per core