As an example, if you sleep 8 hours a day, between 10pm to 6am. You can set a timer to turn off the air-con at 3am, your room is likely to stay cool until 6am, effectively saving 3 hours of run time – about 35% of active air-con usage. If it does not stay cool, you could always complement it with a fan. It may not be as cool as having the air-con turned on throughout – but you’ll be pleased to know that doing this can help you save up to $300 annually in energy bills.