Technology Readiness Level (TRL) scale

Every product starts as an idea. If all goes well, it ends up as a reliable product that can be manufactured at scale. Between those two points lies a long process of testing, refinement and scaling up. The Technology Readiness Level, or TRL, is the scale that divides this journey into nine measurable stages. For an SME looking to develop its own product, this scale is far more than just theory. It helps determine when to test, when to invest and when external engineering expertise is needed.

What is Technology Readiness Level (TRL)?

Technology Readiness Level is a scale from 1 to 9 that indicates how mature a technology or product is. TRL 1 represents an initial scientific idea. TRL 9 represents a product that has proven to work in practice and at scale. Each step in between marks tangible progress: from concept to working prototype, and ultimately to a production-ready design.

Origin and purpose of the TRL scale

NASA developed the nine-level TRL scale in the 1970s. NASA used the scale to objectively assess the maturity of space technologies before committing millions to a mission. Since then, other organisations have adopted the model as well, including the European Commission. It uses TRL within Horizon programmes as a standard for assessing the technological maturity of projects.

Why TRL is more than an academic model

The scale originated in the aerospace industry, but the underlying principle applies to any product development process. Each level requires different decisions, involves different risks and calls for a different level of investment. This article translates each TRL level into what it means in practical terms for an SME: which questions to ask, which risks to consider, and when engineering and design for manufacturing become essential.

TRL levels 1 to 9: the scale step by step

The TRL levels 1 to 9 describe a continuous journey from idea to production. In practice, they can be divided into three clusters, each with its own type of risk and its own type of decision-making.

TRL 1–3: idea, concept and initial validation

At TRL 1, you have a basic principle or idea, often little more than a sketch or theory. At TRL 2, you define a specific application concept: what should the idea do, and who is it for? At TRL 3, the first experimental validation takes place, for example through a rough test that demonstrates that the principle works physically.

Think of a consumer electronics start-up developing a new type of locking mechanism. At this stage, you are not building a prototype of the final product. You are only testing whether the core principle holds up. The central question is simple: does the idea work in theory and in an initial test?

TRL 4–6: prototype and test environment

From TRL 4 onwards, you build the first working prototype, usually in a laboratory or test environment with limited similarity to the final production conditions. At TRL 5, the testing becomes more representative: the prototype is tested in an environment that more closely resembles real-world use. TRL 6 demonstrates a prototype that functions in a relevant, realistic environment.

For medical devices, for example, this may mean that a hand-built prototype passes clinically relevant tests, independently of certification or series production. At this stage, the product manager should mainly ask: does the product function under realistic conditions, and what changes are needed before it can be manufactured reliably?

TRL 7–9: production-ready and scaled up

TRL 7 demonstrates a prototype that works in its intended operational environment. TRL 8 means that the product has been fully developed, tested and qualified for production. TRL 9 is the stage at which the product has been proven in series production and is successfully operating in the market.

In mechanical engineering, this can be seen, for example, with a newly developed component. It is first used in a single machine at a customer site (TRL 7). The company then manufactures the component in larger quantities using validated production processes (TRL 8–9). At this stage, the question is no longer whether it works, but how to produce it repeatably, cost-effectively and consistently.

Technical feasibility and risk by TRL level

Each TRL level comes with a different type of risk. Understanding these risks helps you make better investment decisions and avoid costly mistakes later in the development process.

What risks are associated with a low TRL?

At a low TRL, technical uncertainty is the dominant risk. The central question concerns the technical feasibility of the product: does the concept work physically, and is the underlying principle scientifically or technically sound? Investments at this stage remain relatively limited and are focused on testing rather than production equipment.

How risks shift as TRL increases

As the TRL level increases, the risk shifts from “does it work?” to “can we manufacture it, and at what cost?”. At higher TRL levels, the focus moves to production, cost and scalability. Companies that scale up to production too early, without technically validating the intermediate TRL stages, often pay for it later through failed tooling, recalls or unworkable production costs. This is why phased risk management across TRL levels is so valuable. Major investments, such as an injection mould, should only be made once the technical feasibility and the design have been sufficiently proven.

From prototype to production: TRL and design for manufacturing

The transition from prototype to production is where many TRL programmes run into difficulties. A working prototype proves that an idea functions. It does not yet prove that the product can be manufactured efficiently and consistently.

Why a working prototype is not yet a manufacturable product

A sensor that works in a laboratory under controlled conditions (TRL 4) is very different from that same sensor being weather-resistant, cost-effective and suitable for volume production (TRL 8). Bridging that gap requires engineering work: optimising wall thicknesses, selecting the right materials and simplifying assembly. This is precisely where engineering and design for manufacturing make the difference.

The turning point where engineering becomes essential

As a product moves from TRL 6 to TRL 7, design for manufacturing becomes essential. At this stage, you determine how a part will be accommodated in the mould, which tolerances are achievable and how to keep assembly costs low. From a TRL perspective, this is exactly where the transition from prototype to production requires the most attention. A solid DFM guide provides practical support when making these decisions.

Practical examples of TRL scaling across different industries

The TRL framework is universal, but the challenges vary considerably between industries. Two general examples illustrate this.

Consumer products and plastic components

An SME with a working hand-built prototype (TRL 4–5) often runs into difficulties once the product needs to be manufactured in plastic and at scale. Wall thicknesses, tooling and material selection require a different type of expertise from the initial concept phase. For consumer products, the main focus is on unit cost, aesthetics and ease of assembly at scale.

Technical and industrial applications

For technical or industrial applications, such as measuring equipment or a machine component, the focus is more on reliability under load, material certification and service life. The TRL journey still follows the same path, from initial idea to proven production. However, the tests and standards associated with each level can differ significantly from those used in consumer electronics.

When should you involve a development partner at each TRL level?

Not every TRL level requires the same level of support. Early in the development process, you can often work independently or with limited external input. As you move closer to production, specialised expertise becomes increasingly essential.

Early stage: consultation and concept validation

At TRL 1–3, discussing feasibility is often sufficient: having a knowledgeable sounding board to help assess the concept and its initial validation. The investment remains relatively limited. The main goal is to clearly define what you want to build and who you are building it for.

Critical phase: scaling from prototype to production

The transition from TRL 4–6 to TRL 7–9 is where many development projects stall without the right engineering and manufacturing expertise. PEZY supports companies every day, from the first sketch to an injection-moulding-ready component, and sees first-hand where projects run into difficulties between concept and production. It is precisely at this critical stage, around TRL 3 to 6, that involving a development partner with end-to-end expertise in both engineering and product development can make the difference. This helps prevent a well-functioning prototype from failing later because of a production issue that is costly to resolve.

Frequently asked questions about Technology Readiness Levels

Is TRL the same as a product development phase?

Not quite. TRL describes the technological maturity of a product. A product development phase often also includes project-related aspects, such as planning, budget and team structure. The two generally progress in parallel, however: a higher TRL level usually corresponds to a later stage of product development.

How do you determine the TRL level of your product?

Look at the test environment and the evidence you already have. If your product only works in a controlled laboratory setup, it is probably around TRL 4–5. If it is already running consistently in series production, you are moving towards TRL 8–9. If you are unsure, assess each level from the previous sections and identify which questions you still cannot answer with confidence.