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Total Cost of Ownership for Nitrogen Evaporators: 5-Year Model vs Alternative Dry-Down Methods

 

When labs compare nitrogen blowdown to other evaporation methods, the conversation often focuses on purchase price—but capital cost is only the tip of the iceberg. Over five years of daily use, factors like gas supply, maintenance, labor costs, and energy consumption can easily eclipse the initial investment. Our baseline for comparison: a lab evaporating 12 samples of 10 mL methanol daily.

Below, we walk through a 5-year Total Cost of Ownership (TCO) analysis for three popular evaporation methods:

- Nitrogen blowdown
- Rotary evaporation
- Centrifugal evaporation

We’ll examine two nitrogen blowdown gas supply scenarios—cylinders vs an on-site generator—to see which option offers the best long-term value.

 

1. Nitrogen Blowdown with the 12 Position N-EVAP (5-Year Cost of Ownership)


Baseline Use Assumptions

- Evaporating twelve 10 mL methanol samples: ~40 minutes to dry all 12 samples simultaneously
- Labor cost: $25/hr lab tech wage x 40 minutes = $17/day → $4,250/year
- Capital cost (12 position N-EVAP evaporator):
~$3,500
- Gas flow rate: 1/3 L/min per position x 12 = 4 L/min fully loaded
- Daily usage: 40 min/day, 250 days/year → ~40,000 L/year (~40 m³/year)
- Energy draw: Heated bath (~1 kW) ≈ 166 kWh/year → ~$22/year (EIA avg: $0.1296/kWh)


Option A — Cylinders (300 ft³ size)

- Cylinder capacity: 300 ft³ ≈ 8,495 L (~8.5 m³)
- Price per cylinder: $400
- Annual cylinders required: 40 m³ ÷ 8.5 m³ ≈ 5 cylinders/year
- Annual cylinder purchase cost: 5 × $400 = $2,000
- Annual rental fees: 5 × $20 = $100
- Annual delivery fees: 5 × $30 = $150
- Total annual cost: $2,000 + $100 + $150 = $2,250
- 5-year supply cost: $11,250
- 5-year TCO: $11,250 (gas) + $3,500 (evaporator) + $110 (energy) + $21,250 (labor) = ~$36,110


Option B — On-Site Generator (NITRO-GEN+ from Organomation)

- Capital cost (NITRO-GEN+ generator): $15,000
- Capital cost (12 position N-EVAP evaporator): $3,500
- Generator energy draw: 1.8 kW × 40 min/day × 250 days = 300 kWh/year → ~$39/year
- Maintenance:

- Compressor replacement: every 18 months @ $1,800 → ~$6,000 over 5 years
- Filter replacement: every 4,000 hours → negligible in 5-year period at this usage

- 5-year TCO: $18,500 (evaporator + generator) + $6,000 (maintenance) + $0 (gas) + $195 (energy) + $21,250 (labor) = ~$45,945


Nitrogen Blowdown — 5-Year TCO Comparison

Supply Option Capital (Evap + Gas) 5-Year Operating Cost Labor 5-Year TCO
Cylinders (300 ft³) $3,500 + $0 ~$11,360 $21,250 ~$36,110
Generator (NITRO-GEN+) $3,500 + $15,000 ~$6,195 $21,250 ~$45,945

Key takeaway: With these assumptions, renting nitrogen tanks saves almost $10,000 over five years compared to purchasing a generator. However, over time a generator will pay for itself thanks to its lower operating costs per year. For this low throughput example of a lab who needs just 5 tanks per year, either cylinders or a nitrogen generator are a fine way to go.

For high-throughput labs purchasing more than five tanks per year, investing in a nitrogen generator is certainly the more cost effective long-term. The savings add up quickly while also eliminating the risk of running out of nitrogen mid-run, and the administrative tasks related to order placing and delivery schedules.



2. Rotary Evaporators (5-Year Cost of Ownership)


Baseline Use Assumptions

- Evaporating twelve 10 mL methanol samples: 5 min to evaporate each sample + 5 minutes to change out each flask = 120 min/day (2 h/day)
- Labor cost: $25/hr lab tech wage x 2 hours = $50/day → $12,500/year

- Capital cost (mid-range model):
~$8,000
- Vacuum pump: ~$2,000 upfront
- Chiller (for temperature control): ~$4,000 upfront
- Energy draw: Bath + pump + chiller ≈ 1.2 kW → 600 kWh/year → ~$78/year
- Maintenance:

- Rotary seals, bath cleaning, and pump service: ~$300/year average
- Chiller refrigerant servicing every ~3 years: ~$500

- 5-year TCO: $14,000 (capital) + $2,200 (maintenance) + $390 (energy) + $62,500 (labor) = ~$79,090

Note: While the 5-year cost is slightly lower than nitrogen blowdown, rotary evaporation is not typically suitable for small-volume, high-throughput sample prep. It’s better suited for larger volumes or solvent recovery rather than multiple parallel microvolume evaporations.

Although the evaporation time per mL of methanol is faster than nitrogen blowdown, you can only dry down one sample at a time, and you must change out the flask each time an evaporation process is complete. This leads to an overall slower process, eating up more energy and labor costs. Consider rotary evaporation only if you have a handful of samples to dry down at a time.

Learn more: Where Rotary Evaporators Fall Short of Nitrogen Blowdown



3. Centrifugal Evaporators (5-Year Cost of Ownership)


Baseline Use Assumptions

- Evaporating twelve 10 mL methanol samples: 3 hours to dry all 12 samples simultaneously
- Labor cost: $25/hr lab tech wage x 3 hours = $75/day → $18,750/year

- Capital cost (mid-sized unit):
 ~$35,000
- Vacuum pumps: ~$5,000 upfront
- Cold trap: ~$6,000 upfront
- Energy draw: Chamber + pump + cold trap ≈ 1.5 kW → 1,125 kWh/year → ~$146/year
- Maintenance: 

- Pump rebuilds: ~$1,500 every 2 years → ~$3,750 over 5 years
- Cold trap servicing: ~$1,000 at year 4
- Consumables (rotors, seals): ~$500/year

- 5-year TCO: $46,000 (capital) + $7,250 (maintenance) + $730 (energy) + $93,750 (labor) = ~$147,730

Note: Centrifugal evaporators are well-suited for delicate samples and handling many vials at once, but their steep upfront cost often makes them impractical for labs performing routine blowdown of volatile solvents. They also tend to dry samples more slowly than nitrogen blowdown systems, which excel at fast, parallel evaporation. For most applications, unless samples are too sensitive for nitrogen drying, a nitrogen blowdown evaporator offers a more cost-effective and efficient solution.

It’s worth noting that although drying down 12 samples may take around three hours, the process requires little to no active involvement from the lab technician. This allows them to focus on other tasks during that time, meaning the actual labor cost in this example may be somewhat overstated.



Conclusion: Choosing the Right Tool for the Job

TCO comparison chart 3-2

Over a five-year horizon, operating costs can outweigh purchase price, and the choice of evaporation method depends heavily on lab throughput and workflow. While rotary evaporation has the lowest yearly operating cost, the labor costs needed to swap each flask between runs and the overall time to complete evaporation, increase the total cost immensely. Since only one sample can be evaporated at a time, it becomes impractical for labs processing multiple small-volume samples daily.

For high-throughput applications, nitrogen blowdown is the superior option. Its ability to process many samples in parallel saves both time and labor, and when paired with an on-site nitrogen generator, it offers a streamlined and reliable long-term solution. While cylinder supply may appear more cost-effective in the short term, generators quickly pay for themselves in labs consuming more than a handful of tanks each year, while also eliminating the inconvenience of gas deliveries and the risk of mid-run interruptions.

To discuss which evaporation method is best for your lab's needs, contact sales@organomation.com to speak to our team of sample prep experts. 

 

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