Hospital administrators evaluating oxygen plant proposals tend to focus on
the purchase price. It's the number at the bottom of the quote. It's the
number the finance committee asks about. It's also the least useful number
for comparing long-term value.
A hospital oxygen plant runs 24 hours a day, 365 days a year, for 15-20
years. Over that lifetime, the purchase price represents roughly 20-30
percent of what you'll actually spend. The other 70-80 percent is
electricity and maintenance - costs that depend entirely on the technology
you chose during procurement.
10-year TCO = Capital Cost + (Annual Electricity x 10) + (Annual
Maintenance x 10) + (Sieve Replacement Cost x Replacements over 10 years)
+ (Annual Management Cost x 10)
Step 1: Capital Cost (Real, All-In)
Get the supplier's installed price including equipment, freight,
installation labor, commissioning, pipeline and electrical connections,
and civil works. Don't accept an ex-works price - that number leaves 30-50
percent of actual costs off the table.
For a dual-unit 40 Nm3/h installation: PSA ~$100,000-$140,000 installed;
VPSA/VSA ~$140,000-$200,000 installed.
Step 2: Annual Electricity Cost
Ask the supplier for a guaranteed specific power consumption (kW/Nm3).
Formula: Specific power x Annual oxygen production x Electricity rate.
PSA at 1.7 kW/Nm3, 150,000 Nm3/year at $0.10/kWh: $25,500/year.
VSA at 0.8 kW/Nm3, same output and rate: $12,000/year.
Annual difference: $13,500. Over 10 years: $135,000.
Step 3: Annual Maintenance Cost
PSA: $15,000-$25,000/year (oil changes, filters, coalescing filters,
carbon filters, condensate treatment, valve rebuilds, sensor calibration).
VSA: $3,000-$6,000/year (air filter replacement, booster service, sensor
calibration, annual inspection).
Step 4: Molecular Sieve Replacement
PSA sodium zeolite: replacement every 2-3 years at $20,000-$32,000 per
event. Over 10 years: 3-4 replacements = $60,000-$128,000.
VSA lithium zeolite: replacement at year 10-12. Over 10 years: $0.
Worked Example: PSA vs VSA at 40 Nm3/h, 60% Load Factor
PSA 10-year TCO:
- Capital: $120,000; Electricity: $165,000; Maintenance: $200,000;
Sieve: $112,000; Management: $50,000
- Total: $647,000
VSA 10-year TCO:
- Capital: $170,000; Electricity: $80,000; Maintenance: $50,000; Sieve:
$0; Management: $15,000
- Total: $315,000
10-year difference: $332,000 in favor of VSA.
- Capital (tank installation): $30,000
- Gas cost: 150,000 Nm3/year x $0.55/Nm3 x 10 = $825,000
- Delivery surcharges and boil-off: $55,000
- Total: $910,000
LOX is the most expensive option over 10 years, despite the lowest upfront
capital.
Adjusting the Model for Your Hospital
1. Get your actual electricity rate from your utility bill, not the
published industrial rate.
2. Get your actual oxygen consumption from 12 months of meter readings.
3. Get maintenance cost data from reference hospitals running each
technology - not supplier estimates.
4. Factor in your local labor rates. In regions where qualified
technicians are scarce, VSA's reduced maintenance burden is even more
valuable.
5. Run sensitivity analysis: what if electricity rates increase 50
percent? The TCO advantage of VSA is robust across a wide range of
assumptions.