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Cost-Effectiveness: Total Cost of Ownership – It’s the Big Picture That Counts
The technical superiority of optical bonding has been thoroughly demonstrated in the previous chapters. However, in the reality of investment decisions, technical excellence alone is rarely enough. The crucial question is: Is the investment worth it? This concluding chapter translates the technical advantages into the language of business economics and demonstrates that optical bonding is the superior choice not only technically but also economically. The key lies in understanding the Total Cost of Ownership (TCO) — the total costs over the entire lifespan of the system, not just the purchase price.
Beyond the Price Tag: The TCO Concept
Focusing on the purchase price is one of the most common and costly mistakes made when procuring industrial equipment. A cheaper HMI module may look attractive on the invoice, but if it fails after two years, causing production downtime and requiring expensive repairs, it was the more expensive choice.
The Total Cost of Ownership (TCO) is a financial evaluation method that captures all costs incurred over the entire lifespan of an asset. These include not only the initial purchase but also operation, maintenance, downtime, and disposal. TCO forces decision-makers to think beyond the current fiscal year and evaluate the long-term financial implications of their decisions.
The acquisition costs include the purchase price, installation, staff training, and commissioning. Operating costs include energy, consumables, and license fees. Maintenance costs consist of preventive maintenance, repairs, and replacement parts. Downtime costs — often the largest and most underestimated item — include lost productivity, opportunity costs, and reputational damage. Finally, disposal costs include dismantling, recycling, and disposal fees.
Total Cost of Ownership (TCO) berechnen:
The TCO formula is conceptually simple, but its application requires an honest and complete accounting of all cost components:
TCO = Acquisition + (Operating × Years) + (Maintenance × Years) + (Failure Rate × Downtime Costs × Years) + Disposal
For a precise analysis, future costs must be discounted using the Net Present Value (NPV) to account for the time value of money. A euro today is worth more than a euro tomorrow. (Original quote: A dollar today is worth more than a dollar tomorrow)
A Comparison of Cost Structures: Air Gap vs. Optical Bonding
To demonstrate the economic superiority of optical bonding, a detailed comparison of cost structures over the product’s lifecycle is necessary.
Acquisition Costs:
Here, the air-gap display has a clear advantage. Optical bonding requires additional materials (the optical adhesive, the edge sealing), a more complex manufacturing process, and more rigorous quality control. The additional costs typically range between 10% and 30% of the purchase price of an air-gap display. For a heavy-duty HMI that costs €5,000 as an air-gap variant, the optically bonded version would cost approximately €6,500 in the worst-case scenario—a difference of €1,500.
Operating costs:
Energy consumption is lower with optical bonding, as the higher transmission allows for reduced backlighting. A significant advantage lies in cleaning: Air-gap displays show dust and dirt that accumulates in the air gap more clearly and require more frequent cleaning. Optical bonding completely eliminates this problem.
Maintenance costs:
As explained in "Failure Modes and Their Analysis", the failure rate of air-gap displays is three to five times higher than that of optically bonded displays. Internal condensation, dust ingress, and mechanical breakage are the main causes. Every failure requires a repair or replacement. Even if the repair is covered by warranty, costs are incurred for logistics, the technician’s labor, and downtime. Over ten years, these costs add up significantly. Assuming an air-gap display requires an average of €300 per year in maintenance costs, while an optically bonded display requires only €100 per year, this results in a difference of €2,000 over ten years.
Downtime costs:
This is the factor that dominates the TCO calculation. Downtime costs are not the cost of the repair, but the cost of the machine being out of service. Consider a construction machine such as an excavator with a purchase price of €500,000, which is in operation for 2,000 hours per year and generates revenue of €150 per hour. If the HMI fails, the entire machine comes to a standstill. Downtime costs amount to €150 per hour in lost revenue plus approximately €200 per hour for the technician who travels to the site, diagnoses the problem, and performs the repair—a total of €350 per hour. An average repair takes eight hours (including travel, diagnosis, procurement of the replacement part, and installation), resulting in costs of €2,800 per outage. If an air-gap display fails once over ten years (a conservative assumption based on a 10% failure rate), this results in €2,800 in downtime costs. An optically bonded display with a failure rate of less than 2% fails statistically only 0.2 times, resulting in downtime costs of €560. The difference of €2,240 already exceeds the additional purchase cost.
Disposal costs:
These are similar for both technologies and play a minor role in the TCO calculation. However, an optically bonded display must be disposed of later due to its longer service life, which also reduces disposal costs over multiple product lifecycles.
The TCO Calculation:
A Concrete Example
Let’s summarize the cost components in a concrete calculation, based on a useful life of ten years:
Air-Gap Display:
- Purchase price: €5,000
- Maintenance (10 years at €300 per year): €3,000
- Downtime (1 outage at €2,800): €2,800
- Total TCO: €10,800
Optically bonded display:
- Purchase: €6,500
- Maintenance (10 years at €100): €1,000
- Failures (0.2 failures at €2,800 each): €560
- Total TCO: €8,060
TCO savings in the scenario considered: €2,740 (25% lower)
Despite a 30% higher purchase cost, the optically bonded display is 25% cheaper over its lifetime. The break-even point — the point at which the cumulative costs of both options are equal — is reached after about three to four years. From that point on, every additional year of operation saves money.
The return on investment (ROI) is calculated as:
ROI = TCO savings / Additional investment × 100% = €2,740 / €1,500 × 100% = 183%.
In other words: Under the assumptions made, every additional euro invested in optical bonding generates a calculated net benefit of approximately €1.83 over a ten-year period.
Sensitivity Analysis: When Is Optical Bonding Particularly Worthwhile?
The TCO calculation is not universal. It depends on the specific conditions of the application. A sensitivity analysis reveals which factors have the greatest influence.
Failure costs are the most critical factor. In applications with extremely high failure costs—such as in medical technology, where a failure of a diagnostic device can endanger human lives, or in aviation, where a failure of a cockpit display would have catastrophic consequences—optical bonding is not only economically superior but practically without alternative. Even in less critical applications such as infotainment systems, where failure costs are lower, optical bonding remains advantageous due to reduced maintenance costs, albeit with a smaller margin.
The failure rate itself depends heavily on the environment. In humid, dusty, or high-vibration environments, air-gap displays fail significantly more often. In controlled indoor environments, the difference is smaller but still significant.
The service life is another key factor. With a short service life of just five years, the TCO advantage of optical bonding is smaller but still present. With a service life of 15 or 20 years—as is common in rail vehicles or industrial control systems — the advantage becomes significant.
The discount rate used to calculate the NPV influences the valuation of future savings. A higher discount rate makes future savings less valuable and reduces the TCO advantage. A lower discount rate enhances it.
Non-monetary benefits: Value that cannot be measured in euros
In addition to the directly quantifiable cost savings, optical bonding offers a range of benefits that are difficult to quantify in euros but still create real value.
Safety: More reliable displays reduce the risk of accidents caused by malfunctions or poor readability. In safety-critical applications such as automotive, aviation, or medical technology, this is invaluable.
Compliance: Many industry standards and regulations require high reliability. Optical bonding makes it easier to meet these requirements and avoids liability risks.
Productivity: Better readability leads to faster operation and fewer errors. Reduced eye strain due to higher contrast reduces fatigue and increases operator efficiency over long shifts.
Brand Image: High-quality, reliable displays signal quality and professionalism. They strengthen the brand image and customer satisfaction. A customer whose machine never stops due to a display failure becomes a repeat buyer and brand ambassador.
Sustainability: A longer service life means less electronic waste and lower resource consumption over the product lifecycle. At a time when sustainability is increasingly becoming a competitive factor, this is an advantage that should not be underestimated.
Residual value: After ten years, an optically bonded display that still functions flawlessly has a higher resale value than an air-gap display, which may already show signs of condensation, scratches, or other signs of degradation.
The Decision Matrix: A Tool for Rational Choice
Investment decisions are complex and must take multiple criteria into account. A decision matrix helps to weigh the various factors and arrive at a rational decision.
In such a matrix, criteria such as acquisition costs, operating costs, maintenance costs, downtime costs, and service life are listed and assigned weights that reflect their relative importance for the specific application. For a heavy-duty application, the weighting might look like this: acquisition costs 20%, operating costs 10%, maintenance costs 25%, downtime costs 35%, service life 10%. Each option (air gap vs. optical bonding) is evaluated for each criterion, and the weighted scores are totaled.
The result is clear: Optical Bonding performs significantly better in the weighted categories, particularly in terms of maintenance costs, downtime costs, and service life. Air Gap leads only in terms of acquisition costs, but this category has a lower weighting of 20% in the overall context of the decision matrix.
Conclusion: Investing in Reliability Pays Off
The economic analysis shows unequivocally: Optical bonding is not only technically superior, but also the smarter choice economically. The higher upfront costs are more than offset by drastically lower maintenance and downtime costs. The TCO is significantly lower over the product’s lifespan, the ROI is attractive, and the break-even point is reached after just a few years.
But the calculation goes beyond mere numbers. Optical bonding offers security, compliance, higher productivity, a stronger brand image, and a contribution to sustainability. It is an investment in reliability, quality, and long-term success.
For decision-makers who think beyond the next quarter and understand the true value of their investments, the choice is clear. Optical bonding is not a cost center, but rather a sustainable source of value and an investment in the future.
| Criterion | Weighting | Air Gap | Optical Bonding |
|---|---|---|---|
| Initial Costs | 20% | ++ | - |
| Operating Costs | 10% | 0 | + |
| Maintenance Costs | 25% | -- | ++ |
| Downtime Costs | 35% | -- | ++ |
| Service Life | 10% | - | ++ |
| Weighted Result | 100% | Low | High |
Rating scale: ++ = very favorable, + = favorable, 0 = neutral, − = unfavorable, −− = highly unfavorable.
References
Reliability.com. (2025, April 23). FMEA Guide: Failure Mode and Effects Analysis Step-by-Step.
Ansys. (2023, October 25). What Is DFMEA? Design Failure Mode and Effect Analysis.
Relyence. (2019, June 27). Guide to Weibull Analysis & Life Data Analysis for Reliability.
ScienceDirect. (o. D.). Bathtub Curve - an overview.
Gregory Poole. (2025, August 29). Understanding Total Cost of Ownership for Heavy Equipment.
Ansys. (o. D.). What Is Design for Reliability (DfR)?.
Note on the technical information in this chapter
The technical values, test profiles, and performance data stated in this chapter are provided for technical classification purposes. Actual results depend on the specific display configuration, material system, bonding process, application profile, and scope of qualification. Product-specific values are validated on a project basis using data sheets, measurements, test reports, and customer specifications.