Higher or lower fridge temperature
Refrigerators are heat engines, and the energy cost is somewhat proportional to the difference in temperature desired.  Assuming your room temperature is typical, higher internal refrigerator temperatures are going to therefore take less energy to maintain.

Modern refrigerators are well insulated and remarkably energy efficient.

You should choose the the temperature setting of your refrigerator based on the quality and safety of the foods stored within, which indicates a temperature of about 32-40°F (0-4°C).

Too cold may freeze food, which can lead to quality issues, but is safe.  Too warm can allow food to spoil, which is a far greater risk.

See also:


What is the ideal fridge temperature
What temperatures should I keep my refrigerator and freezer set at?