5 Steps to Evaluate an On-Site Gas Supply Proposal (From a Procurement Perspective)

I've been managing service procurement for a mid-sized manufacturing plant for about six years now. When I took over purchasing in 2020, one of the first big projects was evaluating on-site gas supply proposals. At the time, I figured it was like buying any other utility—compare prices, pick the lowest. That first evaluation taught me a lesson I'm still paying for, in a way.

This checklist is for anyone who's sitting down with a proposal like that—from an operations manager to a plant engineer who's been handed the evaluation task. It's not about the chemistry of gas separation or the engineering specs of the air separation unit. It's about how to evaluate the proposal so you don't get burned by things that aren't on the front page. Here's a 5-step process I now use for every on-site supply deal.

Step 1: Understand Your Baseline Needs, Not Just Your Current Bill

The biggest rookie mistake I see (and made myself) is assuming your current consumption pattern is your baseline. In my first year, I made the classic specification error: assumed 'standard' meant the same thing to every vendor. Cost me a $600 redo when we realized one proposal was sized for our average peak load, and another for our continuous average.

Here's what you need to nail down before you look at proposals:

• Actual monthly consumption for the past 24 months, not just your annual average. Gas demand isn't flat.
• Peak demand events. What happens when two production lines ramp up simultaneously? Your supply needs to cover that, or the proposal will add 'peak shaving' costs.
• Purity requirements. A supplier quoted us for 'standard industrial grade' nitrogen. The spec we needed was 99.995%. That mismatch showed up in the delivery volume, not the price per unit on the summary sheet.

Why does this matter? Because the proposal price is usually per unit of gas, but the system design determines how many units you actually consume. If the system isn't sized for your peaks, you'll buy bottled gas at a massive markup to cover dips.

Step 2: Map Out the Total Cost of Supply, Not Just the Gas Price

I'm not an engineer, so I can't speak to the thermodynamics of the air separation unit itself. What I can tell you from a procurement perspective is that the 'price per thousand cubic feet' is maybe 40% of the story.

In my experience managing 6 on-site vendor relationships over 5 years, the lowest gas price has cost us more in 2 of those cases. Let me give you a real example from a different contract: a $200 savings in monthly gas cost turned into a $1,500 problem when the vendor's power consumption guarantee didn't match the proposal assumption. We ended up paying the difference on our electricity bill.

Ask for these items explicitly:

• Power consumption guarantees with penalty clauses for variance. Get this in the contract, not just the sales deck.
• Maintenance and service frequency. More visits = more downtime for your team to coordinate.
• Liquid backup costs. When the unit goes down (they all do eventually), what's the cost for your liquid supply?
• Termination fees. This is the one nobody talks about. The proposal might have a 10-year term with a fixed price, but the exit cost after year 3 could be brutal.

Step 3: Verify Performance Claims Against Industry Standards

This is where I lean on industry data rather than just vendor claims. The wording 'proprietary gas separation technology' sounds great, but how do you know it's as efficient as stated?

Standard print resolution requirements: 300 DPI for commercial print.
Standard gas separation efficiency claims? Not as neat. But here's a rule of thumb: industry standard for air separation unit power consumption for large-scale nitrogen generation is roughly 0.27-0.35 kWh per Nm3 of nitrogen at 99.9% purity (this varies by scale and purity, obviously). Ask for their specific expected consumption in your conditions.

Reference: Per the US Department of Energy's Industrial Technologies Program benchmark data (accessed via archived publications, 2020), the theoretical minimum energy requirement for air separation is approximately 0.19 kWh/Nm3 for nitrogen, with practical systems operating at 1.5-2x that baseline depending on efficiency and scale.

If a proposal claims 0.20 kWh/Nm3 for a plant your size, you should ask questions. Honest vendors will tell you their range. Over-promising vendors might give you a number that sounds great but is actually beyond what physics allows.

Step 4: Evaluate the Service and Maintenance Plan (The Part You'll Hate Later)

Here's something from a procurement perspective that often gets overlooked: the on-site supply proposal is a relationship contract, not a product purchase. You're committing to someone monitoring, maintaining, and potentially owning equipment on your site for years.

• Who monitors the unit? Is it remote and reactive, or do they have local techs?
• What's the guaranteed response time for a failure? Ours promised 4 hours. Real world? I've had a 12-hour wait more than once.
• Spare parts inventory. Do they stock parts locally, or do they ship from a central warehouse? That adds days, not hours.

We didn't have a formal approval chain for service escalation procedures. Cost us when an unauthorized weekend service call showed up on the invoice for $2,400. The third time we had a delay because we didn't confirm who coordinates site access, I finally created a contact checklist. Should have done it after the first time.

Step 5: Negotiate the Non-Price Terms (Where the Real Value Lives)

If you ask me, the negotiation isn't really about the gas price. That part is usually pretty fixed by market rates. The real value is in the terms you negotiate around the price.

Here's what I'd push on:

1. Start-up dates. When does the clock start ticking on the term? From contract signing, from equipment delivery, or from when the system is running and producing? There's a big difference.
2. Price review mechanisms. Ask for a clear formula tied to an independent index (like US Energy Information Administration data for natural gas/electricity), not just 'we'll talk in year 3'.
3. Early exit terms. Even if you plan for 10 years, ask what happens if your plant closes or changes ownership. You don't want to owe millions for equipment you can't use.
4. Performance credits. If the unit doesn't meet guaranteed purity or flow, how do you get compensated? Don't just let it slide with 'we'll fix it.'

Honestly, I never fully understand why vendors resist the performance credit language so much. My best guess is that it forces them to size the system with a bigger buffer, which makes their proposal less competitive on paper. So they push back. Push back harder.

Common Pitfalls to Avoid

Let me save you some hassle:

• Don't assume 'turnkey' means 'no extra costs.' Turnkey usually covers the equipment and installation. It might not cover the concrete pad, electrical runs, or permits you need.
• Don't trust the 'standard' purity claim without verifying. I made that mistake. Twice.
• Don't forget about site access. If your plant is behind a security gate that closes at 5 PM, your 24/7 service guarantee is worth a lot less unless the vendor knows how to use the after-hours access code.

This will probably work for most on-site supply evaluations, at least for the non-engineering part. The specific savings percentages will vary—I'm not 100% sure, but in my experience, a thorough evaluation like this will save you between $5,000 and $15,000 over the first 2 years of a typical contract, mostly from not overpaying on power penalties or avoidable liquid backup. Don't hold me to that exact number, but it's a rough estimate.