Refrigerators are often overlooked in the Freezer Challenge, probably because they're missing from the title ;) But they are very important, being far more ubiquitous than any other type of cold storage, including ULTs and -20s. In fact, we estimate that there are nearly 1 million refrigerators in labs across the United States alone.
Did you know there are currently 52 ENERGY STAR-certified lab grade refrigerators listed on the EPA's website? And if you don't need a high performance refrigerator, there are literally thousands of residential ENERGY STAR-certified models to choose from. The most efficient refrigerators are those with solid doors, so consider switching away from sliding glass door models if you need to purchase a new refrigerator or replace an old one.
Of course, the most efficient refrigerator is the one you don't have to buy. Remember to inventory and clean out your refrigerators before June 15th - you'll be earning points that many will have forgotten about!