Most kitchens are designed to have triangular relationships between the stove and oven, refrigerator and sink. Wall ovens can be placed in kitchens with a corresponding hob. Ovens can be placed next to the refrigerator, but in the design community, it is regarded as a flaw.
Wall ovens that are placed next to the refrigerator can create heat inside the refrigerator, causing it to run more, shortening the life of the unit and creating higher energy bills. Refrigerators and ovens that have good insulation, however, are less likely to use extra energy even when they are adjacent to each other.
An oven that is next to a refrigerator will not have counter space on both sides of the oven, making it inconvenient to remove hot food from the oven. The refrigerator may not have a counter close by, also making it awkward for taking out heavy items.
When designing a kitchen, applying the triangle rule creates the most efficient layout for cooking. The sink, stove and refrigerator should be within an easy walk from each other. All the major appliances should have some counter space next to them, even if the space is small.