Update customisation.md

docs/customisation.md

@@ -62,9 +62,12 @@ especially on more complex tariffs like Agile when run on lower power machines s
 You can tweak **input_number.predbat_calculate_plan_every** (_expert mode_) to reduce the frequency of replanning while
 keeping the inverter control in the 5 minute slots. E.g. a value of 10 or 15 minutes should also give good results.
 
-If you have performance problems leave **switch.predbat_calculate_second_pass** (_expert mode_) turned off as it's
+If you have performance problems leave **switch.predbat_calculate_second_pass** (_expert mode_) turned Off as it's
 quite CPU intensive and provides very little improvement for most systems.
 
+If you have performance problems leave **switch.predbat_calculate_fast_plan** (_expert mode_) turned On to help 
+reduce your CPU load.
+
 ## Battery loss options
 
 **input_number.battery_loss** accounts for energy lost charging the battery, default 0.05 is 5%
@@ -151,6 +154,11 @@ if **car_charging_planned** is set correctly in apps.yaml to detect your car bei
 
 See the Predbat mode setting as above for basic calculation options
 
+**switch.predbat_calculate_fast_plan** (_expert mode_) When True (default) the plan is calculated with a limited number of
+windows to make calculations faster. When False all windows are considered but planning will take a little longer but be 
+more accurate. The end result is unlikely to change in fast mode as the next windows are always considered but the longer
+term plan will be last accurate.
+
 **switch.predbat_calculate_discharge_oncharge** (_expert mode_) When True calculated discharge slots will
 disable or move charge slots, allowing them to intermix. When False discharge slots will never be placed into charge slots.