diff --git a/code/controllers/subsystem.dm b/code/controllers/subsystem.dm
index cd029b58ed8..be9c8a88032 100644
--- a/code/controllers/subsystem.dm
+++ b/code/controllers/subsystem.dm
@@ -97,9 +97,9 @@
 	return
 
 //This is used so the mc knows when the subsystem sleeps. do not override.
-/datum/controller/subsystem/proc/ignite(resumed = 0)
+/datum/controller/subsystem/proc/ignite(resumed = FALSE)
 	SHOULD_NOT_OVERRIDE(TRUE)
-	set waitfor = 0
+	set waitfor = FALSE
 	. = SS_SLEEPING
 	fire(resumed)
 	. = state
@@ -114,7 +114,7 @@
 //previously, this would have been named 'process()' but that name is used everywhere for different things!
 //fire() seems more suitable. This is the procedure that gets called every 'wait' deciseconds.
 //Sleeping in here prevents future fires until returned.
-/datum/controller/subsystem/proc/fire(resumed = 0)
+/datum/controller/subsystem/proc/fire(resumed = FALSE)
 	flags |= SS_NO_FIRE
 	CRASH("Subsystem [src]([type]) does not fire() but did not set the SS_NO_FIRE flag. Please add the SS_NO_FIRE flag to any subsystem that doesn't fire so it doesn't get added to the processing list and waste cpu.")
 
diff --git a/code/controllers/subsystem/air.dm b/code/controllers/subsystem/air.dm
index e8e6f9209ac..61c9c3e953d 100644
--- a/code/controllers/subsystem/air.dm
+++ b/code/controllers/subsystem/air.dm
@@ -6,6 +6,7 @@ SUBSYSTEM_DEF(air)
 	flags = SS_BACKGROUND
 	runlevels = RUNLEVEL_GAME | RUNLEVEL_POSTGAME
 
+	var/cached_cost = 0
 	var/cost_turfs = 0
 	var/cost_groups = 0
 	var/cost_highpressure = 0
@@ -40,7 +41,6 @@ SUBSYSTEM_DEF(air)
 	var/list/queued_for_activation
 	var/display_all_groups = FALSE
 
-	var/lasttick = 0
 
 /datum/controller/subsystem/air/stat_entry(msg)
 	msg += "C:{"
@@ -78,76 +78,101 @@ SUBSYSTEM_DEF(air)
 	var/delta_time = wait * 0.1
 
 	if(currentpart == SSAIR_REBUILD_PIPENETS)
+		if(!resumed) //We track the use for each subprocess for the full tick, so we can get an acccurate idea of how much each part costs
+			cached_cost = 0
 		var/list/pipenet_rebuilds = pipenets_needing_rebuilt
 		for(var/thing in pipenet_rebuilds)
 			var/obj/machinery/atmospherics/AT = thing
 			AT.build_network()
-		cost_rebuilds = MC_AVERAGE(cost_rebuilds, TICK_DELTA_TO_MS(TICK_USAGE_REAL - timer))
+		cached_cost += TICK_USAGE_REAL - timer
 		pipenets_needing_rebuilt.Cut()
 		if(state != SS_RUNNING)
 			return
+		cost_rebuilds = MC_AVERAGE(cost_rebuilds, TICK_DELTA_TO_MS(cached_cost))
 		resumed = FALSE
 		currentpart = SSAIR_PIPENETS
 
 	if(currentpart == SSAIR_PIPENETS || !resumed)
+		timer = TICK_USAGE_REAL
+		if(!resumed)
+			cached_cost = 0
 		process_pipenets(delta_time, resumed)
-		cost_pipenets = MC_AVERAGE(cost_pipenets, TICK_DELTA_TO_MS(TICK_USAGE_REAL - timer))
+		cached_cost += TICK_USAGE_REAL - timer
 		if(state != SS_RUNNING)
 			return
+		cost_pipenets = MC_AVERAGE(cost_pipenets, TICK_DELTA_TO_MS(cached_cost))
 		resumed = FALSE
 		currentpart = SSAIR_ATMOSMACHINERY
 
 	if(currentpart == SSAIR_ATMOSMACHINERY)
 		timer = TICK_USAGE_REAL
+		if(!resumed)
+			cached_cost = 0
 		process_atmos_machinery(delta_time, resumed)
-		cost_atmos_machinery = MC_AVERAGE(cost_atmos_machinery, TICK_DELTA_TO_MS(TICK_USAGE_REAL - timer))
+		cached_cost += TICK_USAGE_REAL - timer
 		if(state != SS_RUNNING)
 			return
+		cost_atmos_machinery = MC_AVERAGE(cost_atmos_machinery, TICK_DELTA_TO_MS(cached_cost))
 		resumed = FALSE
 		currentpart = SSAIR_ACTIVETURFS
 
 	if(currentpart == SSAIR_ACTIVETURFS)
 		timer = TICK_USAGE_REAL
+		if(!resumed)
+			cached_cost = 0
 		process_active_turfs(resumed)
-		cost_turfs = MC_AVERAGE(cost_turfs, TICK_DELTA_TO_MS(TICK_USAGE_REAL - timer))
+		cached_cost += TICK_USAGE_REAL - timer
 		if(state != SS_RUNNING)
 			return
+		cost_turfs = MC_AVERAGE(cost_turfs, TICK_DELTA_TO_MS(cached_cost))
 		resumed = FALSE
 		currentpart = SSAIR_EXCITEDGROUPS
 
 	if(currentpart == SSAIR_EXCITEDGROUPS)
 		timer = TICK_USAGE_REAL
+		if(!resumed)
+			cached_cost = 0
 		process_excited_groups(resumed)
-		cost_groups = MC_AVERAGE(cost_groups, TICK_DELTA_TO_MS(TICK_USAGE_REAL - timer))
+		cached_cost += TICK_USAGE_REAL - timer
 		if(state != SS_RUNNING)
 			return
+		cost_groups = MC_AVERAGE(cost_groups, TICK_DELTA_TO_MS(cached_cost))
 		resumed = FALSE
 		currentpart = SSAIR_HIGHPRESSURE
 
 	if(currentpart == SSAIR_HIGHPRESSURE)
 		timer = TICK_USAGE_REAL
+		if(!resumed)
+			cached_cost = 0
 		process_high_pressure_delta(resumed)
-		cost_highpressure = MC_AVERAGE(cost_highpressure, TICK_DELTA_TO_MS(TICK_USAGE_REAL - timer))
+		cached_cost += TICK_USAGE_REAL - timer
 		if(state != SS_RUNNING)
 			return
+		cost_highpressure = MC_AVERAGE(cost_highpressure, TICK_DELTA_TO_MS(cached_cost))
 		resumed = FALSE
 		currentpart = SSAIR_HOTSPOTS
 
 	if(currentpart == SSAIR_HOTSPOTS)
 		timer = TICK_USAGE_REAL
+		if(!resumed)
+			cached_cost = 0
 		process_hotspots(delta_time, resumed)
-		cost_hotspots = MC_AVERAGE(cost_hotspots, TICK_DELTA_TO_MS(TICK_USAGE_REAL - timer))
+		cached_cost += TICK_USAGE_REAL - timer
 		if(state != SS_RUNNING)
 			return
+		cost_hotspots = MC_AVERAGE(cost_hotspots, TICK_DELTA_TO_MS(cached_cost))
 		resumed = FALSE
 		currentpart = SSAIR_SUPERCONDUCTIVITY
 
 	if(currentpart == SSAIR_SUPERCONDUCTIVITY)
 		timer = TICK_USAGE_REAL
+		if(!resumed)
+			cached_cost = 0
 		process_super_conductivity(resumed)
-		cost_superconductivity = MC_AVERAGE(cost_superconductivity, TICK_DELTA_TO_MS(TICK_USAGE_REAL - timer))
+		cached_cost += TICK_USAGE_REAL - timer
 		if(state != SS_RUNNING)
 			return
+		cost_superconductivity = MC_AVERAGE(cost_superconductivity, TICK_DELTA_TO_MS(cached_cost))
 		resumed = FALSE
 	currentpart = SSAIR_REBUILD_PIPENETS