Machinery: Always use update_use_power()

code/modules/shieldgen/emergency_shield.dm

@@ -134,7 +134,7 @@
 	var/is_open = 0 //Whether or not the wires are exposed
 	var/locked = 0
 	var/check_delay = 60	//periodically recheck if we need to rebuild a shield
-	use_power = 0
+	use_power = USE_POWER_OFF
 	idle_power_usage = 0
 	var/global/list/blockedturfs =  list(
 		/turf/space,
@@ -156,7 +156,7 @@
 	idle_power_usage = 0
 	for(var/obj/machinery/shield/shield_tile in deployed_shields)
 		idle_power_usage += shield_tile.shield_idle_power
-	update_use_power(1)
+	update_use_power(USE_POWER_IDLE)
 
 /obj/machinery/shieldgen/proc/shields_down()
 	if(!active) return 0 //If it's already off, how did this get called?
@@ -166,7 +166,7 @@
 
 	collapse_shields()
 
-	update_use_power(0)
+	update_use_power(USE_POWER_OFF)
 
 /obj/machinery/shieldgen/proc/create_shields()
 	for(var/turf/target_tile in range(2, src))

code/modules/shieldgen/sheldwallgen.dm

@@ -23,7 +23,7 @@
 		//There have to be at least two posts, so these are effectively doubled
 		var/power_draw = 30000 //30 kW. How much power is drawn from powernet. Increase this to allow the generator to sustain longer shields, at the cost of more power draw.
 		var/max_stored_power = 50000 //50 kW
-		use_power = 0	//Draws directly from power net. Does not use APC power.
+		use_power = USE_POWER_OFF	//Draws directly from power net. Does not use APC power.
 
 /obj/machinery/shieldwallgen/attack_hand(mob/user as mob)
 	if(state != 1)

code/modules/shieldgen/shield_capacitor.dm

@@ -15,7 +15,7 @@
 	var/max_charge = 8e6	//8 MJ
 	var/max_charge_rate = 400000	//400 kW
 	var/locked = 0
-	use_power = 0 //doesn't use APC power
+	use_power = USE_POWER_OFF //doesn't use APC power
 	var/charge_rate = 100000	//100 kW
 	var/obj/machinery/shield_gen/owned_gen
 

code/modules/shieldgen/shield_diffuser.dm

@@ -4,7 +4,7 @@
 	description_info = "This device disrupts shields on directly adjacent tiles (in a + shaped pattern). They are commonly installed around exterior airlocks to prevent shields from blocking EVA access."
 	icon = 'icons/obj/machines/shielding.dmi'
 	icon_state = "fdiffuser_on"
-	use_power = 2
+	use_power = USE_POWER_ACTIVE
 	idle_power_usage = 25		// Previously 100.
 	active_power_usage = 500	// Previously 2000
 	anchored = 1
@@ -57,7 +57,7 @@
 		update_icon()
 		return
 	enabled = !enabled
-	use_power = enabled + 1
+	update_use_power(enabled ? USE_POWER_ACTIVE : USE_POWER_IDLE)
 	update_icon()
 	to_chat(usr, "You turn \the [src] [enabled ? "on" : "off"].")
 

code/modules/shieldgen/shield_gen.dm

@@ -22,7 +22,7 @@
 	var/time_since_fail = 100
 	var/energy_conversion_rate = 0.0006	//how many renwicks per watt?  Higher numbers equals more effiency.
 	var/z_range = 0 // How far 'up and or down' to extend the shield to, in z-levels.  Only works on MultiZ supported z-levels.
-	use_power = 0	//doesn't use APC power
+	use_power = USE_POWER_OFF	//doesn't use APC power
 
 /obj/machinery/shield_gen/advanced
 	name = "advanced bubble shield generator"