Buy the right air-con size for the room. A multi-split unit is ideal for cooling more than 1 room.
Shut windows, doors and seal gaps in door and windows when air-con is in use.
Keep the air filter clean.
Keep the house cool so that the air-con need not require more energy to cool it. Use blinds, curtains, awnings or solar-reflecting film on the windows.
Refrain from opening the door when the oven is in use because the oven temperature could drop 25 to 30 degrees Celsius which implies that more energy is need to heat it back to the preset temperature.
Cook or heat up a few dishes in a mircowave at the same time and do not forget to cover the dishes.
When using aluminium foil in an electric oven to catch drips, do not place it just beside the dish as it will reflect heat away from it, thus more time is needed to heat the food.
Clear away the dust on the cooling coils at least once a year. This helps reduce the energy needed to cool the refrigerator.
Check the rubber seals (gaskets) for leaks - put a piece of paper at the doorway before closing the door and try pulling the piece of paper out. If it slips out easily then it is time to change the rubber lining.
Never overload. Allow space for the cooling air to circulate around.
Place a thermometer (if none built-in) inside the fridge to check if the temperature within is kept between 0 to 4 degrees Celsius while the temperature in the freezer should be -18 degrees Celsius.
When going away for a long holiday, clear the fridge and switch it off.