Dust or vacuum the grills and coils of your refrigerator and freezer regularly, especially in homes where pet hair is abundant. Air spaces between foods in a refrigerator improve cooling efficiency.
Freezers cost less to operate when packed full of food.
Make sure refrigerator door seals fit airtight. Don't use an oven for toasting bread or for heating the house. Plan meals that require as few cooking appliances as possible. For example, cook several dishes in the oven at the same time. Use a timer instead of looking into the oven to see if food is done.