Regardless the cabinet family or type, the heat to be extracted from the cabinet so that inside we have the temperature necessary for the conservation of refrigerated or frozen foods is the sum of the heat losses, plus the heat provided by the electrical elements What is inside.
Losses are caused by convection, radiation, and conduction. The electrical elements inside are fans, lighting, anti-condensation resistors and defrost resistors.
Solutions to optimize energy consumption must be sought in each of these components and sections. And for most of the solutions the starting point is the "design". And the main criterion, the inefficiencies reduction.