How a Delta Plc Evaluation Taught Me to Buy PLCs on Total Cost, Not Sticker Price

In January 2025, I sat in my office with three quotes for the same control panel spread across my desk. The customer had asked for “safety-rated controllers with force-guided relays and documented compliance.” The three quotes varied by about $220 per unit. That doesn’t sound huge, but we build this panel roughly 40 times a year. $220 times 40 is $8,800. A procurement manager on a $180,000 annual budget notices $8,800.

I run procurement at a 150-person custom machinery OEM. I’ve managed our automation component budget for seven years, negotiated with more vendors than I can count—30-plus, if we’re counting—and logged every order in a cost tracking spreadsheet. This is the story of how a mid-project supplier evaluation became a decision that changed how we buy PLCs.

Why We Started Looking

For years, engineering had a favorite PLC brand. I won’t name them, but they’re a well-known automation manufacturer. The controls team loved the programming environment, we had spare modules on the shelf, and our cabinet drawings were built around their form factor. Everything worked. Everything was also getting expensive, and lead times were creeping out.

It started with an end customer’s request for a specific set of controller specifications: scan time under a certain value, enough high-speed inputs for their sensors, Ethernet/IP compatibility, and relay outputs with documented contact reliability. The incumbent could meet it, but the quote came back high and the delivery window was “maybe Q3.”

I asked our distributor for alternatives. That’s when Delta Plc showed up in the conversation.

The First Lesson: Relay Compliance Requirements Are Not a Box to Check

The distributor sent a Delta PLC quote that was roughly 28% lower than the incumbent for comparable modules. My first thought, honestly, was suspicion. I’ve been burned before by low quotes that became high total costs.

So I did what I always do: I built a spreadsheet. Columns for unit price, software, spare parts availability, documentation, training, support, and compliance paperwork. I asked the Delta distributor to walk through each line. To their credit, they didn’t just send a catalog. They asked about our application first.

“Are you using this in a safety circuit or a standard control circuit? Because that changes the relay compliance requirements.”

Good question. Here’s the thing: relay compliance requirements aren’t one generic certification that every relay either has or doesn’t have. According to IEC 61810 (available from webstore.iec.ch), electromechanical relays used in general control circuits have a basic reliability rating. But if you’re using forced-guided relay contacts in a safety circuit, EN 50205 is the standard that applies. And if your panel is headed to North America, UL 508 adds another layer. The distributor’s question told me they were interested in education, not just pushing a part number.

Controller Specifications: What Actually Mattered

The controller specifications we needed turned out to be more straightforward than the compliance side. CPU scan time, communication ports, I/O capacity, ambient temperature rating, and the availability of a safety-rated CPU family. Delta Plc’s lineup had options for each of those. But the real differentiator was how the distributor translated the specs into our application.

As a PLC OEM—in the sense that we integrate PLCs into the machines we sell—we don’t just buy a controller. We buy a platform that our engineers can support for years. The controller specifications have to line up with the end customer’s requirements, but they also have to match our spare parts strategy, our standard drawings, and our programming templates.

The Twist: Delta PLC Software and the Learning Curve

I brought the Delta PLC quote to our lead controls engineer. He looked at it for about 30 seconds and said, “We’d have to learn new software.”

That was a real objection, not a small one. It’s not hard to find projects that stall because someone underrated the learning curve. The cost of switching isn’t just the hardware—it’s the software, the training, the mistakes on a customer’s line, and the time spent rebuilding your standard machine logic.

Delta PLC software is free, which I like. But free doesn’t mean zero cost. The cost is engineering time. Our engineer asked whether it could import our old programs. The answer was no. So we calculated the real cost of the switch: conversion of our standard templates, three engineers’ training time, and validation on the first two builds.

Then we compared that against the unit price savings. It came out to more or less a wash for the first year, with a recurring benefit after that. The incumbent had raised prices 4% to 6% per year for the last three years. The Delta quote included a two-year price lock. That changed the math.

So we did something I’m not normally brave enough to do: we ran a pilot. We ordered Delta PLCs for two machines, kept one incumbent module set on the shelf as a backup, and let the controls engineer work with Delta PLC software on the lab bench for three weeks before the builds.

What the Pilot Taught Us

First, the Delta PLC software was easier than the controls engineer expected. He didn’t love it—he called the interface “fine, not beautiful”—but there were no showstoppers. Second, the documentation was genuinely useful. The relay compliance requirements were laid out in a table with standard references and certificate numbers. For procurement, that’s gold. I could pull the exact certificate and send it to the end customer without five follow-up emails.

Third, and this was the surprise, the distributor’s local application engineer answered our questions faster than the incumbent’s support line. One call about a high-speed input configuration took about 20 minutes. With the old brand, we used to wait up to two days for a support ticket response. Worse than expected, in other words.

Total Cost Reality

What I mean by total cost is not the invoice. It’s engineering time, support responsiveness, shipping lead times, documentation quality, and the risk that something doesn’t work on the Friday before a Monday install with no one to call.

In the first year, we ordered 38 Delta PLCs across three machine models. Total cost—including software licenses, training hours, and one wiring error that was completely our fault—came in 9% lower than the incumbent’s quote for the same quantities. Not 28% lower, because the learning curve ate the difference. Still meaningful.

On a $180,000 budget, 9% is $16,200. I can think of worse ways to spend money.

What This Taught Me

It took me about two years and 40 supplier evaluations to understand that vendor relationships matter more than vendor capabilities. A vendor that asks about your application before talking about price is a partner. A vendor that just sends a quote is a reseller.

Look, I’m not saying budget options are always bad. I’m saying the starting price is one line in a bigger spreadsheet. The Delta Plc route worked for us because we had a patient distributor, a controls engineer willing to try something new, and an application that didn’t require exotic certifications. If you’re in automotive safety systems or marine classification, your calculation might be different. You might need a supplier with a local support engineer who can attend a design review. You might need a specific brand because an end customer has an approved vendor list.

Here’s another insight: compliance documentation can be a competitive advantage. When a machine ships to a plant with strict relay compliance requirements, our team now knows exactly what to show. We’ve started including the compliance table in our own sales documents. Customers don’t ask fewer questions—they ask better questions. An informed customer asks better questions and makes faster decisions.

Advice for Procurement Teams

1. Ask for compliance documents before you issue the PO. If a supplier can’t tell you the relay compliance requirements for their products within 24 hours, that’s a red flag.
2. Calculate the software migration cost. Free PLC software is great, but your engineers’ time isn’t free.
3. Run a pilot, not a full switch. We ordered two machines first. That limited our risk and gave us a basis for comparison.
4. Think in terms of TCO from the start. Don’t hold me to this, but I’d budget at least 20% above the unit price for the true total cost—training, documentation, spares, and the risk margin.

Part of me wishes we had done this two years earlier. The savings would have been nice. But the real win is not the unit price. It’s that our engineering and procurement teams now have a better process for evaluating controller specifications—and our customers get better documentation. Not bad for a hunch and a spreadsheet.

Pricing referenced from early 2025 quotes; verify current rates with your local distributor.

Rebecca Sloan

Rebecca Sloan is a power distribution and protection analyst specializing in circuit breakers, switchgear, contactors, fuses, surge protective devices, and coordination. She applies IEC 60947-2 breaker requirements, IEC 60269 fuse characteristics, and IEC 61643-11 tests while examining rated voltage, breaking capacity, time-current curves, selectivity, and prospective short-circuit current. She helps engineers and buyers compare protective devices against documented fault levels, installation conditions, maintenance access, and continuity priorities.