diff --git a/src/reactor_sim/generator.py b/src/reactor_sim/generator.py
index 5ec7685..d25bba8 100644
--- a/src/reactor_sim/generator.py
+++ b/src/reactor_sim/generator.py
@@ -52,8 +52,11 @@ class DieselGenerator:
         state.battery_output_mw = 0.0
         if state.starting:
             state.spool_remaining = max(0.0, state.spool_remaining - dt)
-            state.power_output_mw = self.rated_output_mw * (1.0 - state.spool_remaining / max(self.spool_time, 1e-6))
-            state.battery_output_mw = min(0.5, load_demand_mw)
+            progress = 1.0 - state.spool_remaining / max(self.spool_time, 1e-6)
+            available = self.rated_output_mw * progress
+            delivered = min(available, max(0.0, load_demand_mw))
+            state.power_output_mw = delivered
+            state.battery_output_mw = min(0.5, delivered) if delivered > 0 else 0.0
             if state.spool_remaining <= 0.0:
                 state.starting = False
                 state.running = True
@@ -61,7 +64,8 @@ class DieselGenerator:
                 LOGGER.info("Generator online at %.1f MW", self.rated_output_mw)
         elif state.running:
             available = self.rated_output_mw
-            state.power_output_mw = min(available, load_demand_mw)
+            delivered = min(available, max(0.0, load_demand_mw))
+            state.power_output_mw = delivered
             state.status = "RUN" if state.power_output_mw > 0 else "IDLE"
         else:
             state.power_output_mw = 0.0