diff --git a/spinn_machine/version/version_3.py b/spinn_machine/version/version_3.py
index f81b40c0..b8dc36e4 100644
--- a/spinn_machine/version/version_3.py
+++ b/spinn_machine/version/version_3.py
@@ -32,6 +32,10 @@ class Version3(VersionSpin1):
     """
     __slots__ = ()
 
+    #: From measuring the power of an idle 4-chip board for 1 hour, the cost
+    #: is 3.56W
+    WATTS_FOR_4_CHIP_BOARD_IDLE_COST: Final = 3.56
+
     @property
     @overrides(VersionSpin1.name)
     def name(self) -> str:
@@ -98,7 +102,9 @@ def get_idle_energy(
             raise SpinnMachineException(
                 "A version 3 SpiNNaker 1 board has exactly one board!")
 
-        return n_chips * self.WATTS_PER_IDLE_CHIP * time_s
+        # 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
 
     @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 ecd56e46..92dc2b29 100644
--- a/spinn_machine/version/version_5.py
+++ b/spinn_machine/version/version_5.py
@@ -52,14 +52,16 @@ class Version5(VersionSpin1, Version48Chips):
     WATTS_PER_FRAME_ACTIVE_COST_OVERHEAD: Final = 154.163558 - 117
 
     # pylint: disable=invalid-name
-    #: measured from the real power meter and timing between the photos
-    #: for a day with just the cooling fans of the boxed board.
-    WATTS_FOR_48_CHIP_BOX_COST_OVERHEAD: Final = 4.5833333
+    #: from Optimising the overall power usage on the SpiNNaker neuromimetic
+    #: platform, an idle board uses 26.84W and from measurement of a boxed
+    #: board with all cores idle for 1 hour including the power supply and all
+    #: parts, uses 31.88W, so the overhead is 5.04W
+    WATTS_FOR_48_CHIP_BOX_COST_OVERHEAD: Final = 5.04
 
     # pylint: disable=invalid-name
-    #: measured from the real power meter and timing between the photos
-    #: for a day powered off
-    WATTS_FOR_48_CHIP_BOARD_IDLE_COST: Final = 4.5833333
+    #: from Optimising the overall power usage on the SpiNNaker neuromimetic
+    #: platform, an idle board uses 26.84W
+    WATTS_FOR_48_CHIP_BOARD_IDLE_COST: Final = 26.84
 
     @property
     @overrides(VersionSpin1.name)
@@ -109,8 +111,9 @@ def fpga_links(self) -> List[Tuple[int, int, int, int, int]]:
     def get_idle_energy(
             self, time_s: float, n_frames: int, n_boards: int,
             n_chips: int) -> float:
-        # Chips idle energy
-        energy = n_chips * self.WATTS_PER_IDLE_CHIP * time_s
+
+        # The board idle energy
+        energy = n_boards * self.WATTS_FOR_48_CHIP_BOARD_IDLE_COST * time_s
 
         # The container of the boards idle energy
         if n_frames != 0:
@@ -121,8 +124,6 @@ def get_idle_energy(
                     n_frames * self.WATTS_FOR_48_CHIP_BOX_COST_OVERHEAD *
                     time_s)
 
-        # The FPGAs + board idle energy, excluding the chips
-        energy += n_boards * self.WATTS_FOR_48_CHIP_BOARD_IDLE_COST * time_s
         return energy
 
     @overrides(VersionSpin1.get_active_energy)
diff --git a/spinn_machine/version/version_spin1.py b/spinn_machine/version/version_spin1.py
index b0287913..a3eef5e3 100644
--- a/spinn_machine/version/version_spin1.py
+++ b/spinn_machine/version/version_spin1.py
@@ -28,15 +28,10 @@ class VersionSpin1(AbstractVersion, metaclass=AbstractBase):
     Shared code for all Spin1 board versions
     """
 
-    #: stated in papers (SpiNNaker: A 1-W 18 core system-on-Chip for
-    #: Massively-Parallel Neural Network Simulation)
-    #: (includes Idle chip @ 360mW, SDRAM @ 170mW and idle cores @ 20mW each)
-    WATTS_PER_IDLE_CHIP: Final = 0.360 + 0.170 + (0.02 * 18)
-
-    #: stated in papers (SpiNNaker: A 1-W 18 core system-on-Chip for
-    #: Massively-Parallel Neural Network Simulation)
-    #: = (1000mW - WATTS_PER_IDLE_CHIP - (6.3mW for each link)) / 18 ~= 4mW
-    WATTS_PER_CORE_ACTIVE_OVERHEAD: Final = 0.004
+    #: 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
+    #: 59.37W active, so 27.49W active overhead, which is 0.034W per core
+    WATTS_PER_CORE_ACTIVE_OVERHEAD: Final = 0.034
 
     #: stated in papers (SpiNNaker: A 1-W 18 core system-on-Chip for
     #: Massively-Parallel Neural Network Simulation)