Larger refrigerators burn more energy than smaller ones, but it is more energy efficient to buy one large refrigerator than two smaller ones of comparable combined volume. A smaller refrigerator and a separate freezer unit also consume more electricity than a single large combination refrigerator/freezer.
Apart from size, one of the most important factors in refrigerator energy efficiency is age. Newer models of refrigerator, especially those with U.S. Environmental Protection Agency Energy Star certification, are up to 75 percent more energy efficient than older models, as of 2015. The difference is so extreme that some states have rebate programs that offer to reimburse part of the purchase price to consumers if they trade in older refrigerator models and purchase newer more energy-efficient ones.
Newer refrigerators offer better performance due to more efficient temperature control, compressors, insulation and defrosting ability. However, modern conveniences such as ice makers and dispensers drastically reduce energy efficiency, and energy-conscious consumers should purchase refrigerator models without these extras or run the fridge with the ice maker off.
Although refrigerators with freezers on top are the most energy efficient, top-freezer models are not available in large sizes. Large refrigerators with bottom freezers are more energy efficient than side-by-side models.