Military off-the-shelf (MOTS)

COTS vs MOTS: Military Off‑The‑Shelf Power Supplies Explained

When the US government started looking for ways to save money and speed up development cycle time, they started looking at using commercially available products to satisfy their program needs. These types of products are known as COTS – commercial off-the-shelf. In defense acquisition, the term ‘COTS meaning’ refers to commercially available COTS products that can be adapted for program use. These commercial products often need to be tweaked to meet the rugged environments many military programs encounter.

COTS Meaning in Defense Programs

In defense acquisition, COTS military programs use commercially available products to reduce cost and accelerate development timelines. However, COTS components often require ruggedization or modification when they will operate in harsh military environments like vibration, humidity, salt spray, dust, or altitude.

COTS vs MOTS: What’s the Difference?

COTS (commercial off‑the‑shelf) products are packaged, commercially available solutions that can be adapted to a program’s needs. MOTS (modified off‑the‑shelf), sometimes called military off‑the‑shelf, typically starts from a rugged COTS baseline and is modified to better match military environmental and electrical requirements. In practice, COTS vs MOTS often comes down to speed and budget versus fit and environmental specificity. For defense programs, choosing the right starting point can reduce lead time and lower development risk.

Military COTS Power Supply: When to Use It (and When to Go MOTS)

A military COTS power supply is a commercially available power supply used in defense programs to reduce cost and shorten development timelines. In many cases, COTS military hardware is the fastest way to begin integration and early testing—especially when the program can accept a standard mechanical package and the power requirements are well understood.

When a Military COTS Power Supply Is a Good Fit

A military COTS power supply is typically the right starting point when your program priorities are speed, budget, and getting to a testable configuration quickly. Consider COTS if:

• You need to start system integration or lab testing immediately and can’t wait for a full custom design cycle.
• Your electrical requirements are common and stable (for example, standard bus voltages and a known power range).
• Your environment is controlled enough that standard rugged features (or minimal additional screening) are sufficient.
• You can work within an existing form factor, connector scheme, and mounting approach.
• You want to prove system architecture first, then refine requirements based on test results.

In short, COTS products are ideal for get moving fast phases, when you’d rather validate the system than over-engineer the power solution too early.

When You Should Go MOTS (Modified / Military Off‑The‑Shelf)

You should strongly consider MOTS when a standard COTS unit is close, but not quite right for the real-world environment or electrical edge cases your platform will see. MOTS is often the better fit when:

• The platform introduces harsh conditions (temperature extremes, shock, vibration, altitude, humidity, dust, salt spray).
• You have stricter EMI/EMC requirements and need additional filtering or design changes to support compliance targets (often driven by MIL‑STD‑461).
• The input bus is messy (crank, load dump, transients, brownouts, frequency variation), and you need better ride-through or protection.
• You need modifications like different input/output ranges, multiple outputs, hold-up time changes, different connectors, packaging changes, or mechanical options.
• Your procurement wants the speed and risk profile of an established design, but engineering needs a tighter match to real requirements.

MOTS is the practical middle ground. You keep the advantages of COTS availability while tailoring performance and ruggedness to reduce integration risk.

Quick Rule of Thumb

If you’re still proving the system and your requirements may change, start with military COTS to move quickly. If testing is showing failures in the real operating environment, or you’re designing for mission-critical reliability from day one, move to MOTS so the power supply matches the platform, not just the lab bench.

Standards and Platforms: Where COTS vs MOTS Decisions Often Show Up

Many COTS vs MOTS decisions are driven by the platform’s electrical bus and compliance expectations. For example:

• Airborne power often pushes you toward stricter input and performance requirements (commonly associated with MIL‑STD‑704).
• Ground vehicle power commonly centers around a 28V nominal bus and harsh electrical transients (often associated with MIL‑STD‑1275).
• Naval/shipboard environments can introduce unique interface and power quality constraints (often associated with MIL‑STD‑1399).
• Environmental durability expectations are frequently guided by MIL‑STD‑810, and EMI/EMC expectations by MIL‑STD‑461.

MOTS is born

Over time, COTS has morphed into MOTS (modified off-the-shelf or military off-the-shelf) where programs look to ruggedized COTS to meet the benefits of COTS products. These products are often designed at the manufacturer’s expense to be robust and rugged to meet the challenges of different environments like humidity, salt spray, dust, rain, high altitude, intense shock levels, rough vibration levels, etc. These MOTS software products offer the ability to be easily modified for a fee to meet program-specific needs.

Various military standards that MOTS products can meet are MIL-STD-704 (aircraft), MIL-STD-1275 (ground vehicle), MIL-STD-1399 (naval/shipboard/boat), MIL-STD-810 (environments), and MIL-STD-461 (EMI). All of these specifications have different requirements, so no one product can meet all of them simultaneously but will be designed to meet a certain set of requirements. For instance, a ruggedized COTS, aka MOTS, power supply listing compliance to MIL-STD-704 will meet at least one of the input voltage requirements such as 115 VAC, single phase, 60 Hz. A COTS power supply for ground will meet the MIL-STD-1275 voltage input requirements of 28V nominal input.

Common Standards for COTS and MOTS Power Supplies

• MIL‑STD‑704: aircraft electrical input requirements (air)
• MIL‑STD‑1275: ground vehicle electrical input requirements (land)
• MIL‑STD‑1399: shipboard power interface requirements (sea)
• MIL‑STD‑810: environmental ruggedization (temperature, vibration, shock, etc.)
• MIL‑STD‑461: EMI/EMC requirements for sensitive electronics

ACT and MOTS

At Advanced Conversion Technology (ACT), we have been a designer and manufacturer of custom power supply solutions for over 40 years, meeting various military standards. In the last few years, we have seen the need to offer rugged COTS products, aka MOTS, to meet the quick needs of programs while also meeting the demands of the various requirements. We realize that COTS military products provide a quicker solution for customers to start testing their systems than waiting (and paying) for a custom solution with all the bells and whistles.

As the customer’s testing progresses, the specifications will become more defined, leading to a final version of the product to meet their system requirements. This final version may become custom and have some associated funding, but it will take less time and less money than a completely new solution. To see how we can help you meet your specifications, review our AC‑DC power supplies and DC‑DC power supplies, including rugged MIL‑COTS options. You can also explore our AC‑DC COTS model SW2512 and DC‑DC COTS model SW2511, or talk to an engineer about your MOTS requirements.

If you want to start with a military COTS power supply and evolve toward MOTS as requirements firm up, ACT can help you choose the best starting point and define what modifications will deliver the most risk reduction per dollar. Explore our AC‑DC and DC‑DC power supplies, including rugged MIL‑COTS options, or talk to an engineer about your program requirements.