diff --git a/code/modules/power/lighting/light.dm b/code/modules/power/lighting/light.dm
index 2a2d7e46581..122867b4718 100644
--- a/code/modules/power/lighting/light.dm
+++ b/code/modules/power/lighting/light.dm
@@ -18,8 +18,6 @@
 	var/base_state = "tube"
 	///Is the light on?
 	var/on = FALSE
-	///compared to the var/on for static calculations
-	var/on_gs = FALSE
 	///Amount of power used
 	var/static_power_used = 0
 	///Luminosity when on, also used in power calculation
@@ -66,6 +64,8 @@
 	var/bulb_emergency_pow_mul = 0.75
 	///The minimum value for the light's power in emergency mode
 	var/bulb_emergency_pow_min = 0.5
+	///Power usage - W per unit of luminosity
+	var/power_consumption_rate = 20
 
 /obj/machinery/light/Move()
 	if(status != LIGHT_BROKEN)
@@ -202,17 +202,25 @@
 		use_power = IDLE_POWER_USE
 		set_light(l_range = 0)
 	update_appearance()
-
-	if(on != on_gs)
-		on_gs = on
-		if(on)
-			static_power_used = brightness * 20 //20W per unit luminosity
-			addStaticPower(static_power_used, AREA_USAGE_STATIC_LIGHT)
-		else
-			removeStaticPower(static_power_used, AREA_USAGE_STATIC_LIGHT)
-
+	update_current_power_usage()
 	broken_sparks(start_only=TRUE)
 
+/obj/machinery/light/update_current_power_usage()
+	if(!on && static_power_used > 0) //Light is off but still powered
+		removeStaticPower(static_power_used, AREA_USAGE_STATIC_LIGHT)
+		static_power_used = 0
+	else if(on) //Light is on, just recalculate usage
+		var/static_power_used_new = 0
+		var/area/local_area = get_area(src)
+		if (nightshift_enabled && !local_area?.fire)
+			static_power_used_new = nightshift_brightness * nightshift_light_power * power_consumption_rate
+		else
+			static_power_used_new = brightness * bulb_power * power_consumption_rate
+		if(static_power_used != static_power_used_new) //Consumption changed - update
+			removeStaticPower(static_power_used, AREA_USAGE_STATIC_LIGHT)
+			static_power_used = static_power_used_new
+			addStaticPower(static_power_used, AREA_USAGE_STATIC_LIGHT)
+
 /obj/machinery/light/update_atom_colour()
 	..()
 	update()
diff --git a/tgui/packages/tgui/interfaces/Apc.js b/tgui/packages/tgui/interfaces/Apc.js
index 1bcf7956ea7..4a2752daf72 100644
--- a/tgui/packages/tgui/interfaces/Apc.js
+++ b/tgui/packages/tgui/interfaces/Apc.js
@@ -187,6 +187,7 @@ const ApcContent = (props, context) => {
             label="Cover Lock"
             buttons={(
               <Button
+                tooltip="APC cover can be pried open with a crowbar."
                 icon={data.coverLocked ? 'lock' : 'unlock'}
                 content={data.coverLocked ? 'Engaged' : 'Disengaged'}
                 disabled={locked}
@@ -196,6 +197,7 @@ const ApcContent = (props, context) => {
             label="Emergency Lighting"
             buttons={(
               <Button
+                tooltip="Lights use internal power cell when there is no power available."
                 icon="lightbulb-o"
                 content={data.emergencyLights ? 'Enabled' : 'Disabled'}
                 disabled={locked}
@@ -205,6 +207,7 @@ const ApcContent = (props, context) => {
             label="Night Shift Lighting"
             buttons={(
               <Button
+                tooltip="Dim lights to reduce power consumption."
                 icon="lightbulb-o"
                 content={data.nightshiftLights ? 'Enabled' : 'Disabled'}
                 onClick={() => act('toggle_nightshift')} />