Yes, fridge size has a direct impact on the power consumption. For example, if you purchase 5-star rated refrigerator of 260L and compare it with 5-star rated 180L fridge. Lesser capacity fridge will consume 70 to 80 units less power than the higher capacity one. Also it is important to understand that a refrigerator provides complete value for money when they run at full capacity. So, understand your capacities and choose a model carefully to save your money.