Hi Reader, last week we found out that an ULT freezer leaves a footprint of up to 50 000 kg of CO2 in its lifetime.
Today, we will discover what we can do to reduce the impact of our cooling systems and how significant these measures can be.
I also created the first-ever chart showing how freezer energy consumption has developed over the last few decades for you.
Without further ado, let’s jump in!
Today's Lesson: Saving Energy with Freezers
What you can do to reduce the impact of your freezers
Number Of The Day
The global freezer market in 2022 was estimated at a staggering $4.7 billion. However, by 2030, estimates predict it will grow to between $7.4 billion and $12.7 billion. While the EU and US markets are the largest, Asian markets are expanding rapidly. Nevertheless, it is notable that Africa and South America—despite having significantly hotter climates—accounted for less than 5% of the market in 2024.
4 700 000 000
Making Freezers More Sustainable
As we discussed in our last lesson, the biggest environmental impact of ultra-low temperature (ULT) freezers comes from their use phase.
But how big is their energy consumption compared to other lab equipment?
Freezers run 24/7, so their energy consumption varies only with factors like air temperature and the number of samples stored. For other instruments, specific protocols were developed to resemble "average use."
The average energy consumption of a freezer per year ranges between 2.5 - 9.1 million Wh. An average American household consumes between 9 and 11 million Wh per year. Thus, only the older models consume more energy than an entire home!
Now that we have a sense of scale, let’s explore how to minimize freezer energy consumption as much as possible.
Purchasing
At first, choosing a freezer with lower energy consumption will be environmentally beneficial.
Modern ULT freezers have become significantly more energy efficient over the past few decades.
A 500+ L model from before 2000 can be expected to use up to 36 kWh/day, whereas models from the 2000s–2005s typically consume around 19 kWh/day.
Please note that you should be able to click on the picture to enlarge it. Importantly, the years of release are rough estimates. For none of the freezers, there was information on their precise release date available. Variations could easily be 3-5 years, especially for the older units. All shown models have a storage volume of 520-590L. The regression line suggests that we have about 1kWh/year reduction in energy needs. The * indicates that these consumption data were mathematically extrapolated, not actually measured. All other data was taken from manufacturers.
More recent models have further improved efficiency, consuming between 7–12 kWh/day, with the most efficient freezer currently available (PHCBI) using just 4.99 kWh/day.
These efficiency gains are the result of multiple technological advances:
Vacuum-insulated panels have replaced polyurethane foam, reducing heat loss.
Variable-speed and dual-stage compressors adjust power dynamically, operating only at the minimum required level rather than running at full power constantly.
However, even the best freezers age. Every year, energy consumption increases by approximately 1-3%, which can easily translate to an additional 8.75 kg of CO₂e per month. A summary of when to purchase a new freezer can found in our free Slack.
Adjusting Set Temperatures
The single most impactful change a lab can make is adjusting freezer temperatures from -80°C to -70°C or lower.
Based on studies from the University of Copenhagen, together with an investigation by Farley et al., and manufacturer data, we can confidently say that raising the temperature from -80°C to -70°C reduces energy consumption by 22–29%!
In fact, -70°C was the standard for decades before improvements in cooling technology made -80°C the norm—not for scientific reasons, but because it became a marketing advantage.
Published studies further confirm that sample stability is not affected:
Espinel-Ingroff et al. successfully recovered 6,000+ yeast and 300+ mold samples after 10 years of storage at both -70°C and -80°C.
Landor et al. found no significant degradation in DNA and RNA stored at -70°C, with only minor 260/230 ratio variations, all well below standard deviation ranges.
Paraoxonase-1 enzyme activity remained unchanged after one year of storage at -70°C.
Shown are some RNA concentrations measured with a Qubit 2.0 (ThermoFisher) by Landor et al.
Even manufacturers acknowledge this—QIAGEN officially recommends storing RNA at -70°C.
And it’s not just ULT freezers—adjusting standard freezers from -25°C to -20°C has been shown to reduce energy consumption by 20%, as reported by EPFL in Switzerland.
The Role of Proper Setup and Maintenance
Aside from temperature adjustments, proper installation and maintenance can significantly reduce a freezer’s energy consumption.
A study by Gumapas et al. analyzed four freezers (20–25 kWh/day) under different conditions and found several key factors:
Controlling Ambient Temperature
Each 1°C increase in room temperature leads to 18 kWh of extra energy use per month, releasing an additional 9.27 kg of CO₂e. (+ don't place freezers at windows/in the sun)
Avoiding Dust Accumulation
Regular cleaning can save 211 kWh per month, preventing 108 kg of CO₂e emissions.
Shown is the influence of dust accumulation on freezer filters and condenser fins. In a well-maintained freezer, the compressor can almost completely shut off, whereas in a poorly maintained one, it runs nearly continuously. This is why insufficiently maintained freezers are more likely to fail—typically due to compressor overload.
Declogging filters alone reduced energy consumption by 117 kWh per month, or 60 kg of CO₂e.
Ensuring Ventilation
In their case, poor ventilation increases the duty cycle by 4%, leading to an additional 85 kWh of electricity used per month (equivalent to 51 kg of CO₂e).
Removing Ice
Heavy ice accumulation can increase energy use by up to 50%, forcing the compressor to work harder to maintain low temperatures. (Next week more on how to clean your freezer)
Applying The Knowledge
Should You Purchase Larger Freezers?
Older studies suggest that larger freezers were more about 13% for efficient. However, this depends on the manufacturer. While such a difference is still exists for PHCBI models, they do not in Eppendorf ULTs.
Of note, upright freezers tend to consume less electricity than chest freezers.
How to Convince Colleagues to Switch to -70°C
If your lab is hesitant, the best strategy is to start with one freezer and demonstrate that it is completely safe.
In fact, due to reduced compressor load, freezers set to -70°C are less likely to fail under suboptimal maintenance or when air conditioning struggles to keep up.
If you would like to demonstrate how much money can be saved though purchasing more efficient freezers, PHCBI has a simple online tool (just note that their competitors have newer models with smaller energy consumption).
Upcoming Lesson:
How to Maintain Freezers
How We Feel Today
References
Gumapas, L., Simons, G., 2012. Factors affecting the performance, energy consumption, and carbon footprint for ultra-low temperature freezers: Case study at the National Institutes of Health. World Review of Science, Technology and Sustainable Development, (), –. doi:10.1504/WRSTSD.2013.050786.
Espinel-Ingroff, A., Montero, D., Martin-Mazuelos, E., 2004. Long-term preservation of fungal isolates in commercially prepared cryogenic microbank vials. J. Clin. Microbiol., 42(3), 1257–1259. doi:10.1128/JCM.42.3.1257-1259.2004.
Landor, L.A.I., et al., 2024. DNA, RNA, and prokaryote community sample stability at different ultra-low temperature storage conditions. Environ. Sustain., 7, 77–83. doi:10.1007/s42398-023-00297-2.
Beekhof, P.K., Gorshunska, M., Jansen, E.H., 2012. Long-term stability of paraoxonase-1 and high-density lipoprotein in human serum. Lipids Health Dis., 11, 53. doi:10.1186/1476-511X-11-53.
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