An apartment is considered to be a one-bedroom efficiency if it has a single large room with a combined sleeping and living space and a private bathroom. Efficiency apartments may or may not have a closet, and they often have a small kitchen, also called a kitchenette.
The appliances in efficiency apartments are often smaller and might include a half fridge, a one- or two-burner stove and a small sink. There are advantages to living in an efficiency apartment: the utilities might be added to the rent, they're easy to keep clean and they can often be rented on a monthly basis. One disadvantage of efficiency apartments is the limited storage space, which might require a tenant to rent a separate storage unit.