Is Your -20 Freezer Really a ULT Freezer?
We've been conducting a study on the energy consumption of -20C freezers, and during our field research we've found quite a few ULT freezers set to -20C. That got us thinking: how much more energy does a ULT freezer set to -20 use than a typical -20C freezer? And while the data we've collected are still preliminary, it looks like it's 5 - 10x more. Yikes. Setting your ULT freezer to -70C is a great idea; setting your ULT freezer to -20C probably isn't the most efficient way to store samples at that temperature.
If you're wondering if your ULT freezer is masquerading as a -20 freezer, just check the nameplate. Most ULT model numbers start with 'ULT', and most ULT nameplates are on the outside of the freezer. Minus 20 freezer model numbers do not include the letters 'ULT', and their nameplates are typically located on the inside of the freezer. And if you do find out that your -20 freezer is actually a ULT, you may want to consider a freezer swap with someone else in the department, or find a colleague willing to share space in their freezer. You may even be able to work with facilities management to purchase a commercial freezer - the energy savings from unplugging that ULT would make the payback 1-2 years.