Air conditioners are one of the highest power consuming devices in houses or industrial buildings. Most buildings require air conditioner to make offices, classrooms, public areas or rooms to meet the required thermal comfort. Split unit type air conditioners are widely used in Negara Brunei Darussalam and other ASEAN countries. Currently, prescheduled controllers for split-unit air conditioners are not available in the market. In order to reduce air conditioner power consumption, study have been done to measured energy saving by controlling air conditioning using prescheduled controller that designed which is suitable for fixed operation hours example offices, schools, shops and others. Result showed that average percentage of power saving using a prescheduled controller can be as high as 40%.