diff --git a/Assets/Scripts/ServerShared/Behaviors/Thermotoggle.cs b/Assets/Scripts/ServerShared/Behaviors/Thermotoggle.cs
index 05a354d8b..f2ed29ff0 100644
--- a/Assets/Scripts/ServerShared/Behaviors/Thermotoggle.cs
+++ b/Assets/Scripts/ServerShared/Behaviors/Thermotoggle.cs
@@ -47,8 +47,8 @@ public class Thermotoggle : Behavior
         TargetTemperature = data.TargetTemperature;
     }
 
-    public override bool Execute(float dt)
-    {
-        return Temperature < TargetTemperature ^ _data.HighPass;
-    }
+    // Whether the rest of this behaviour's group runs this tick: below the target, or above it for a high-pass one.
+    public bool Open => Temperature < TargetTemperature ^ _data.HighPass;
+
+    public override bool Execute(float dt) => Open;
 }
\ No newline at end of file
diff --git a/Assets/Scripts/ServerShared/PowerBus.cs b/Assets/Scripts/ServerShared/PowerBus.cs
index 488ea07d2..d0c53b0df 100644
--- a/Assets/Scripts/ServerShared/PowerBus.cs
+++ b/Assets/Scripts/ServerShared/PowerBus.cs
@@ -92,6 +92,16 @@ public class PowerBus
         public Draw(EquippedItem item, int tier, float request) { Item = item; Tier = tier; Request = request; }
     }
 
+    private static bool ClosedByThermostat(EquippedItem item, Behavior consumer)
+    {
+        foreach (var behavior in item.BehaviorGroups[consumer.Data.Group].Behaviors)
+        {
+            if (behavior == consumer) return false;
+            if (behavior is Thermotoggle { Open: false }) return true;
+        }
+        return false;
+    }
+
     public void Step(float dt)
     {
         var reactors = new List<Reactor>();
@@ -119,7 +129,9 @@ public class PowerBus
             // The other direction of the same rule: a consumer switched off or shut down (Active.Value false)
             // never runs its Execute, so it must never be billed either -- otherwise a disabled item's demand
             // starves every live consumer and drains the capacitors for energy nobody spends.
-            if (behavior is IPowerConsumer consumer && item.Active.Value)
+            // And a consumer whose group a thermostat has closed ahead of it does not run this tick either, so it is
+            // not billed: a heater above its target draws nothing.
+            if (behavior is IPowerConsumer consumer && item.Active.Value && !ClosedByThermostat(item, behavior))
             {
                 // Cut 5 (docs/stats-and-power-cut.md §1.3): the item's own stored choice wins once it has one;
                 // PowerTiers.Unassigned only survives past EquippedItem's constructor for a consumer added to
diff --git a/tests/Aetheria.Shared.Tests/RunStartTests.cs b/tests/Aetheria.Shared.Tests/RunStartTests.cs
index e6814f0d2..31ea78fc1 100644
--- a/tests/Aetheria.Shared.Tests/RunStartTests.cs
+++ b/tests/Aetheria.Shared.Tests/RunStartTests.cs
@@ -438,6 +438,54 @@ public sealed class RunStartTests : IDisposable
         Assert.True(coldest > Freezing, $"the heater's cells fell to {coldest} K (station now {station.MinTemp}..{station.MaxTemp} K)");
     }
 
+    // The heater itself warms the station: from a hull at one uniform temperature (so nothing conducts and interior
+    // cells radiate nothing), one tick below the heater's target raises its cells, and one tick above it does not.
+    [Fact]
+    public void AStationHeaterHeatsBelowItsTargetAndNotAbove()
+    {
+        var zone = Arena(new Scenario { Ambient = false }); // no ships: nothing but the zone runs
+        var station = zone.Entities.First(entity => entity is OrbitalEntity && entity.DockingBays.Count > 0);
+        var heater = station.Equipment.Single(IsHeater);
+        var target = heater.Behaviors.OfType<Thermotoggle>().Single().TargetTemperature;
+        for (var tick = 0; tick < 10; tick++) zone.Update(.1f); // the power bus is running
+
+        float Step(float start)
+        {
+            foreach (var v in station.HullData.Shape.Coordinates) station.Temperature[v.x, v.y] = start;
+            zone.Update(.1f);
+            return heater.Temperature - start;
+        }
+        var below = Step(target - 20);
+        var above = Step(target + 20);
+        Assert.True(below > 0, $"below its target the heater's cells moved {below} K");
+        Assert.True(above <= 0, $"above its target the heater's cells moved {above} K");
+    }
+
+    // A consumer runs only when its group's thermostat is open, and is billed only then: a heater above its target
+    // puts no demand on the power bus, below it the bus bills its draw.
+    [Fact]
+    public void AHeaterAboveItsTargetDrawsNoPower()
+    {
+        var zone = Arena(new Scenario { Ambient = false }); // no ships: nothing but the zone runs
+        var station = zone.Entities.First(entity => entity is OrbitalEntity && entity.DockingBays.Count > 0);
+        var heater = station.Equipment.Single(IsHeater);
+        var target = heater.Behaviors.OfType<Thermotoggle>().Single().TargetTemperature;
+        var request = heater.Behaviors.OfType<EnergyDraw>().Single().PowerRequest(.1f);
+        Assert.True(request > 0, "the heater asks for power");
+        for (var tick = 0; tick < 10; tick++) zone.Update(.1f); // the heater is online
+        Assert.True(heater.Active.Value, "the heater is active");
+
+        float Demand(float temperature)
+        {
+            foreach (var v in station.HullData.Shape.Coordinates) station.Temperature[v.x, v.y] = temperature;
+            station.PowerBus.Step(.1f);
+            return station.PowerBus.TotalDemand;
+        }
+        var cold = Demand(target - 20);
+        var warm = Demand(target + 20);
+        Assert.True(cold - warm >= request * .99f, $"demand {cold} below the target, {warm} above; the heater asks {request}");
+    }
+
     // A station hull with no room left for a heater fails its generation by name, rather than spawning a station
     // that will freeze. The only station hull on offer is one whose interior takes the smallest docking bay and no more.
     [Fact]