Economic Modeling

After all the technical assessments—voltage, protocols, inertia, safety—one question remains. 

"Does this retrofit make financial sense?" 

Engineers often treat economics as someone else's problem. That is a mistake. The engineer who can build a credible economic model is the engineer who gets projects approved. The reason is obvious: Economics is not the only driver for retrofits, but it is almost always the first question asked.

For that, we need the tools to answer the following questions with rigor: 

▪ How do we calculate simple payback and return on investment (ROI)? 

▪ How can we model energy savings (the most common retrofit driver)? 

▪ How to account for productivity gains, maintenance reductions, and avoided downtime? 

▪ How do we handle uncertainty and risk in economic models? 

▪ How can we navigate incentives, grants, and carbon accounting?

In the upcoming book: Solutions to Obsolescence, I will try to address these questions and more. 

The Five Compatibility Domains

A retrofit that works is a triumph of engineering efficiency. A retrofit that fails—spectacularly or subtly—is a reminder that old and new systems do not always play well together. The difference is risk assessment performed before the first wire is cut. 

A systematic framework for identifying, evaluating, and mitigating the technical risks of retrofitting is therefore essential. It covers the five critical compatibility domains where old and new systems interact, namely: 

1. Electrical (voltage, current, power quality) 
2. Signal and protocol (communications) 
3. Physical (space, mounting, thermal) 
4. Mechanical (loads, dynamics, wear)
5. Safety (risk migration, integrity levels)

The Venn diagram above provides a visual representation of the five domains in their overlapping relationships. For each domain, the three areas of concern are failure modes, assessment methods, and mitigation strategies.

The Three Drivers of Retrofitting

Retrofitting is not a single activity with a single motivation. It is driven by three distinct forces, often in combination. 

Driver 1: Energy Efficiency 

The most common retrofit driver worldwide. Existing buildings and machines consume energy at levels that would be unacceptable in new installations. Retrofitting can close the gap. 

Driver 2: Functional Modernization (Industry 4.0 / Smart Systems) 

The factory of the future is connected. Sensors, data analytics, predictive maintenance, 

and remote monitoring are becoming standard. But replacing all existing equipment to gain these capabilities is economically impossible.

Driver 3: Safety and Compliance 

Regulations change. A machine that was perfectly safe when built may no longer meet modern standards. Retrofitting can add safety features without replacing the entire machine.

Compliance driver: OSHA, EPA, or local regulations may require upgrades. Retrofitting is often the lowest-cost path to compliance. 

The Paradox of Obsolescence

Consider two machines: 

Machine A is twenty-five years old. Its mechanical systems—the frame, the bearings, the gears, the hydraulic cylinders—are in excellent condition. It was overbuilt in an era when steel was cheap and engineers added safety factors of five or more. This machine will probably outlive its operators. 

But its control system is a relic. The programmable logic controller (PLC) comes from a manufacturer that went out of business fifteen years ago. The user interface is a monochrome screen with a membrane keypad. There is no data port, no network connection, no way to monitor its performance remotely. Replacement parts for the control system are unobtainable except from scavenged units. 

Machine B is brand new. It has a sleek touchscreen interface, cloud connectivity, predictive maintenance algorithms, and energy-optimized servo drives. But its frame is lighter, its bearings are smaller, and its expected service life is ten years—not twenty-five. 

Which machine is more valuable? 

The answer depends entirely on what you value.  

If you need cutting-edge functionality and connectivity, Machine B wins. If you need durability and long-term reliability, Machine A's mechanical bones are superior—but its obsolete brain holds it back.

Retrofitting resolves this paradox. It takes the durable bones of Machine A and gives them the brain of Machine B. The result: a machine that is both durable and modern. 

 

Why Retrofitting Matters

 

Three converging trends have made retrofitting more relevant today than at any point in the last 50 years. 

Trend 1: The Longevity of Physical Assets 

Industrial machinery, commercial buildings, and heavy equipment are built to last 30, 40, or even 50 years. A bridge or a stamping press does not wear out quickly. But the controls that run them—the sensors, controllers, and software—become obsolete every 5 to 10 years. The physical asset has decades of life left. The brain needs an upgrade. Retrofitting connects the two. 

Trend 2: The Energy Efficiency Imperative 

Existing buildings and machines are responsible for a massive share of global energy consumption. Retrofitting—adding LED lighting, variable frequency drives (VFD), smart thermostats, and insulation—is often the fastest, most cost-effective way to reduce carbon emissions from the built environment. The International Energy Agency (IEA) estimates that retrofitting existing buildings could reduce global CO₂ emissions by 30% by 2030—at lower cost than new construction. 

Trend 3: The Digital Transformation of Industry (Industry 4.0) 

Factories are becoming connected. Sensors, data analytics, and predictive maintenance are no longer optional. But replacing a $500,000 machine to gain connectivity is uneconomical. Retrofitting—adding IoT sensors, edge computers, and communication gateways—turns "dumb" machines into smart ones for a fraction of the replacement cost. 

Leave a comment and let me know what you think...

Retrofitting

Retrofitting is the process of adding new features, components, or systems to an existing product—features that were not part of the original design. One of the most significant retrofitting project I've done in my twenty-fives years with ST Electronics is upgrading the disc drive system on the RADCOM test station for the Republic of Singapore Air Force (RSAF).

Believe it or not, the RADCOM test programs—the very heart of its ability to diagnose E-2C avionics—were stored on magnetic cartridges. Not hard drives as we know them today. Not solid-state memory. Magnetic cartridges, about the size of a three-stacked 15-inch pizza, mounted in an HP7906 disc drive and run off an HP1000 host computer.

Over time, the disc access heads of the HP7906 drive built up ferrite dirt. Microscopic particles, accumulated through normal operation, clinging to the heads that read the magnetic media. And when those dirty heads passed over the cartridges, they could cause a head crash—the read head literally scraping against the magnetic surface, scratching it, destroying the data.

It happened more often than anyone liked. Cartridges that had worked for years suddenly became unreadable. Scrap. Trash. Years of test programs, lost to a few microns of ferrite dust. The RSAF was desperate. They had approached Grumman Aerospace—the original equipment manufacturer—for help. Grumman came back with an interim upgrade solution. Price tag: 1.5 million US dollars.

The RSAF project manager reached out to us. After researching for alternative solutions, we decided on the magneto-optical (MO) drive. It uses laser and magnetic technology together, writing data to discs that were far more robust than magnetic cartridges. No head crashes. No ferrite dirt. No scratched media. More importantly, it could be configured to emulate older storage devices. To the host computer, it would look exactly like an HP7906 disc drive. The system wouldn't know the difference. The test programs would load and run exactly as before.

Over the following months, we transferred hundreds of test programs from their vulnerable cartridges to the robust MO discs. Each migration was verified. Each program was tested. By the end, the entire RADCOM test suite lived on media that wouldn't scratch, wouldn't crash, wouldn't fail. 

The cost to the RSAF? Less than half of what Grumman had asked.

The project manager called me after the final acceptance to personally thank me. I appreciated the sentiment. But the real reward was seeing those MO drives spin up day after day, month after month, never losing a single byte of data.

Another obsolescence issue resolved—this time through retrofitting.

Ps: You can read the details and more in my latest book, A Memoir of Electronics, Discoveries, and a Life Less Ordinary by clicking on the book title.

The Hidden Engine of Refurbishing

A novice refurbisher focuses on cleaning and repairing products. A professional refurbisher focuses on flow—a steady, predictable stream of incoming used products (cores) and an efficient, low-cost channel for delivering finished goods to buyers. Refurbishing creates a circular supply chain. Unlike linear manufacturing (raw materials → factory → use → disposal), refurbishing feeds used products back into the value stream. 

If you really want to go into the refurbishing business, you'll need to know about supply chain and reverse logistics, which include the following areas:

▪ Sourcing cores (where used products come from) 
▪ Reverse logistics networks (getting cores to your facility) 
▪ Inventory management (balancing supply and demand) 
▪ Quality variability (handling the unknown) 
▪ Outbound logistics (selling and shipping refurbished units) 

▪ Metrics for a healthy refurbishing supply chain 

I've listed some references for further reading:

▪ Rogers, D. S., & Tibben-Lembke, R. S. (1999). Going Backwards: Reverse Logistics Trends and Practices. Reverse Logistics Executive Council. 
▪ Guide, V. D. R., & Van Wassenhove, L. N. (2009). "The Evolution of Closed-Loop Supply Chain Research." Operations Research, 57(1), 10-18. 
▪ International Organization for Standardization. (2018). ISO 14021: Environmental labels and declarations—Self-declared environmental claims (includes guidance on refurbished claims).

Hope that helps.

 

The Refurbishment Window

Not every product is a good candidate for refurbishing at every point in its life. The figure above illustrates the concept of the refurbishment window. Refurbishing is most valuable when a product has passed its early reliable life but still has significant structural value remaining.

Safety Warning: Never refurbish safety-critical components where failure could cause injury or death. This includes brake components, airbags, medical implants, pressure vessel seals, and aircraft structural parts. Refurbishing is for convenience and cost savings—not for life safety.

The Repair Trap 

One of the most common errors in asset management is the repair trap: repeatedly repairing a product because each repair has low upfront cost, while ignoring the accumulating total cost and downtime. Refurbishing resets the clock at a fraction of replacement cost as the figure below shows:

Despite the virtues of refurbishing, replacement is sometimes unavoidable. So when do you choose repair or replacement over refurbishing? The decision tree below might help:

The choice between repair, refurbish, and replace depends on four criteria: required reliability, available time, budget, and strategic value. 

 

The Refurbishing Workflow

If you're doing a one-off refurbishing job in your daily repair work, then a workflow may not really matter much. But if you're thinking of making refurbishing a sustaining business model then it is imperative to adopt a proper process to ensure success.

Refurbishing follows a repeatable workflow, though the depth of each step varies by product type. Of interest is the first step: Intake/Triage. What exactly is triage, you might ask. In refurbishment, it refers to the initial, rapid assessment and sorting of returned, damaged, or aging items to determine the most cost-effective action: repair, refurbish, resell, or dispose. This process prevents wasting resources on irreparably damaged items and prioritizes those that can be quickly returned to the market. 

You might not realize it but intake triage is the most economically critical stage. A misclassified unit will lose money at every subsequent step. Here's an economic triage rule you would do well to adhere to: 

A product is economically viable for refurbishing if (Resale value of refurbished unit) – (Cost of parts + labor + overhead) ≥ 30% of resale value. That's the minimum margin threshold and it varies by business model. If the margin falls below this threshold, the product is better used as a donor unit or sent to recycling.

A "donor" unit in refurbishing refers to a used, broken, or identical device (often a hard drive, appliance, or electronic component) that is utilized to supply parts for the repair of a "patient" device. This process allows technicians to restore non-functional equipment to working condition by replacing damaged, rare, or obsolete parts that are no longer produced. It's also referred to as "parts harvesting".

It is also important that each unit received during the intake has a unique tracking identifier (serial number, barcode, or RFID). This ID follows the product through all six stages, creating an audit trail. It ensures traceability, compliance, and quality control, providing visibility into the "who, what, and when" of the refurbishing process. 

Bet not many know of such details involved in starting a refurbishing business. There's more but I'll stop here for now. Once I sort out the workflow process in my upcoming book, you'll have the needed information all in one place.