EME 807
Technologies for Sustainability Systems

2.2 Technology readiness levels (TRL)


2.2 Technology readiness levels (TRL)

Technology readiness assessment is a systematic, metrics-based process that evaluates the maturity of, and the risk associated with, critical technologies under development. It is a commonly accepted approach used in a number of industry and government organizations to assess the maturity of a technology (e.g., device, material, component, process, etc.) on an entire scale - from its invention to commercialization and wide-scale application. TRL rating actually determines how far a particular technology is from being deployed by industry or public. That, in turn, determines the amount of resources - time, funds, intellectual potential, facilities, etc., - necessary to bring this technology to life. We can illustrate the term 'readiness' with a simple example like the one below.


For example, I am a researcher at a National Lab working on a small-size methanol fuel cell - a device that can convert the chemical energy of the fuel (methanol in this case) to electricity. I have my fuel cell stack operating in the lab and producing some great data in terms of power density. “It really works!” – I think. But can I put that fuel cell stack on my bike and have a ride home? Well... not right away, at least. The fuel cell system, the way it is set up and operates in the lab, is not ready for immediate use on a bike. I can possibly spend a few more months to work on the adaptation – fixing the fuel cell system on a bike, attaching an electric motor that would transfer the electrical power from the cell stack to the wheel, finding the regulators that would allow me to control the output during a ride, figuring out the position of the methanol fuel source and lines connecting it to the cell… it is quite an engineering project.

But let us imagine that finally I make it work! But can I offer this technology to bikers around town? I used my special knowledge to make all the technical adaptations and to solve multiple challenges, fixing shortcomings. If something is wrong, I know where to find a problem. But a general biker would not like to do all the work I have done and learn all the details I have learned. They would like it simple and fool-proof. I think, the technology, again, is not ready for public yet at that point. And, again, more resources and time are needed to make it user-friendly and more reliable for marketing.

Addendum: I worked on the methanol fuel cell systems in 2001. Years after some companies (Yamaha is one of them) actually managed to create some slick prototypes of fuel cell scooters, like the one shown here. However, it is unclear if any of those made it to the market. If you find any information or references to it, please let me know!

There are many other examples of technology going through many years of adaptation prior to reaching its broad applicability. What you see in the left-side image below may seem like a hardly recognizable mechanical device. What is on the right side is its contemporary version. The first computer mouse prototype was invented in 1964 by Douglas Engelbart of Stanford Research Institute. The mouse device remained an subject for further development, modifications, demos, and pilot projects for two decades before it was finally adapted for broader use with the personal computer Mackintosh 128K in 1984 (Wikipedia)

Enter image and alt text here. No sizes!
Engelbart's first prototype of the comupter mouse (1964) (left); modern look of the computer mouse (right). It took two decades for computer mouse to develop to reach the readiness level for broad adoption and use.
Source: Wikimedia Commons

How do we evaluate the maturity or readiness of a particular technology?


Technology Readiness Level (TRL) scale was first employed by NASA in 1974 to evaluate the maturity of technologies for spacecraft design as part of risk assessment. It was demonstrated that transition of emerging technologies at lesser degrees of maturity results in higher overall risk.

Later, the TRL scale developed by NASA was also adopted in the U.S. by the Department of Defense (DOD), Department of Energy (DOE), Air Force, Oil and Gas Industry and also in Europe by the European Space Agency (ESA). The main rankings in the TRL method for technology readiness assessment are classified in the table below.

Stage of Development Technology Readiness Level Description Outcomes/Supporting Information
Table 2.2. TRL rankings and metrics for technology assessment as adapted from NASA and DOD practice
Basic technology research TRL0 Unproven idea No analysis/testing performed.

Basic Principles observed and reported

Scientific research begins to be translated into applied research and development.

Published research that identified the principles that underlie the concept.
Research to prove feasibility TRL2

Concept formulated

Practical application is invented based on TRL 1. Potential of the applications is speculative and is inferred from general assumptions or some analytical data.

Published research that outlines the application and initial analysis of underlying principles.


Analytical and experimental studies are performed on a lab scale to validate analytical predictions. Work is done on various components of the potential technology (which are not yet integrated).

Experimental data, measured parameters of interest in comparison with analytical predictions.

Lab-scale demonstration (“low fidelity”)

Basic technological components are integrated to establish that they will work together. This is relatively “low fidelity” compared with the eventual system.
Results of laboratory testing. Comparison with system performance goals.
Technology demonstration

Lab-scale demonstration (“high fidelity”)

The basic technological components are integrated with reasonably realistic supporting elements so they can be tested in a simulated environment.

Results of laboratory testing in simulated environment. Identified barriers for target performance goals and plans to overcome them.
System development TRL6

Prototype system designed

The system is integrated with support elements, and model design is created to be tested in simulated or operational environment.

Results of the prototype testing in simulated lab environment. Data are close to target expectations.

Prototype system tested in operational environment

Prototype near or at planned operational system. Represents a major step up from TRL 6 by requiring demonstration of an actual system prototype in an operational environment (e.g., in the field, on aircraft, in a vehicle, or in space).

Results of the prototype testing in operational environment demonstrate success.
System launch and operation TRL8

Actual system completed

The system is qualified through test and demonstration. Technology has been proven to work in its final form and under expected conditions.

Results of testing in its final configuration. Assessment of it meeting its operational requirements. Plans, options, or actions to tune and finalize the design.

Actual system proved successful

Actual application of the technology in its final form and under mission conditions or on market.

Reports on real application performance.

TRL approach proved to be useful as a tool for:

  • general understanding of technology status;
  • risk assessment and management;
  • decision making with respect to technology funding;
  • decision making with respect to technology transfer.

In the context of this course, it will be important to understand the technology readiness levels in order to properly assess the timeline and cost of its development and implementation. When applied to a particular technology, the above listed TRL ranks should be customized for better relevance. Such customization would identify specific milestones as criteria to advance to the next level.

Watch This!

Next, please watch the following video in which Dr. Sean McCarthy (Hyperion Ltd) elaborates on the TRL concept, provides some examples, and examines the ties of TRL assessment to the decision making and choosing partners for a project. This video is made in the context of the european innovation and technlogy implementaiton landscape, but many of those insights are completely transferable to the US soil as well.

Assigning a TRL rank is not a quick task. These are some serious questions that need to be answered and backed by technical data regarding the current status of technology:

  • Is technology widely commercialized?
  • Is technology demonstrated in the final form (in a target system)?
  • Is technology demonstration in the relevant environment (field conditions)?
  • What is the target performance / efficiency level (technically and economically)?
  • What is currently achieved performance / efficiency?
  • What are the materials involved and what is their availability?
  • Is infrastructure available for deployment for this technology?
  • What are the main barriers impeding the higher performance? … etc.

You can see that determining the status of technology development often requires search and knowledge of most recent advances, publications, and news releases on the technical performance, demonstration, pilot systems, and prototypes. It also requires independent expertise in subject matter along with understanding the economic criteria, which establish a threshold where the technology becomes economically feasible and is able to compete with existing alternatives.

What kind of data sources can you use for TRL analysis?

  • Scientific publications in refereed journals
  • Government agency reports
  • Company news releases (may withhold technical details that are proprietary)
  • Public news, web blogs, ads (secondary sources which may refer you to original information)
  • Personal communications with experts, researchers, and enterprenuers 

Try this tool!

Check out this TRL calculator tool, developed by the Advanced Energy Technology Group at University of California San Diego, which can be used to automatically retrieve the TRL value for a particular project based on input scoring on each level criteria. You are welcome to explore it and use it in your course project when determining TRL for the technology of your choice. (Note: the calculator is in MS Excel format. You must enable macros to make it work). This excel file is also available in Module 2 in Canvas. 

I hope you found content on this page useful. Different assignments in this course will tap into the TRL concept repeatedly, and you will be asked to either estimate the TRL ranking or provide some analysis of technology readiness and maturity in your course project. 

Answer this self-check question:

An R&D group in a company developed the design and built a prototype of a new car engine. It has been through a set of comprehensive lab tests, which provide excellent results in terms of system performance. What technology readiness level can be assigned to this development? Click on your answer below.


This would be too low - at this level, the key concept and applications are outlined.


This would be too low - at this level, system components are tested, but they are not yet integrated.


Correct! - at this level, system prototype is tested in the lab under simulated operational conditions.


This would be too high - at this level, the actual system (not prototype) is built and put in real-life operation (without commercialization).

TRL 10

This would be too high - Level 10 is not part of TRL scale but rather denotes commercialized technology.

Additional Resources on Technology Readiness Levels: