Technology Readiness Levels explained: what TRL means for your grant application

What TRL measures

Technology Readiness Levels are a scale for how mature a technology is. They run from TRL 1, basic research, to TRL 9, a technology in everyday use. UKRI, the Aerospace Technology Institute and most other UK funders use the same nine-level scale when they ask applicants to state the starting and target TRL of a project.

The level is not a measure of how clever the idea is. It measures evidence: how far the technology has been proven in a real or representative environment. That is why the same product can contain components at very different TRLs.

TRL 1 to 3: from idea to proof of principle

TRL 1 is basic research. The underlying principles are being observed and reported, often in academic literature, but no one has yet tried to apply them to the specific problem.

TRL 2 moves into applied research. A team starts to formulate how the research might become a practical solution, usually on paper or in simulation.

TRL 3 is proof of concept or proof of principle. An experiment or model shows that the key idea can work in a controlled setting. For example, a new battery chemistry might demonstrate the expected voltage and cycle life in a coin cell made by hand in a lab. It is not yet a product, but the uncertainty has moved from whether the science works to whether it can be engineered.

TRL 4 to 6: validation in the lab and beyond

TRL 4 is technology validation in a laboratory environment. The component or subsystem is built and tested under controlled conditions that mimic some aspect of the final application. A sensor might be validated on a bench with synthetic samples rather than in a real process line.

TRL 5 is validation in a relevant environment. That usually means real materials, real operating conditions, or integration with other real subsystems. A medical device prototype might be tested with ex vivo tissue or early clinical samples rather than just simulant.

TRL 6 is system or subsystem demonstration in a relevant environment. The technology is now being shown as part of a realistic system. For a robotics project, this could be a prototype operating on a factory-like test rig rather than in a clean lab bay.

TRL 7 to 9: demonstration, deployment and use

TRL 7 is system prototype demonstration in an operational environment. The technology works in the setting where it is meant to be used, even if the product itself is not yet final. An agri-tech sensor might be trialled on several real farms across a growing season.

TRL 8 is the actual system completed and qualified through test and demonstration. The product is essentially finished and has been shown to meet its specification under operational conditions.

TRL 9 is the system proven in successful operational service. It is in use with paying customers or end users, with performance data from the field. Very few grant-funded projects aim for TRL 9 within the grant period; most stop at TRL 6, 7 or 8 and leave the final scale-up to commercial investment.

Why a new project in a mature product can still be low TRL

Founders often assume that because their company has a mature product, any new project they propose must be high TRL. That is a costly mistake. A new sensor, algorithm, manufacturing process or formulation added to an existing platform starts its own TRL journey from the bottom.

Imagine a company with a TRL 8 medical imaging device. The team wants to add a new AI reconstruction module. The device is mature, but the module is at TRL 3 or 4: it has shown promise in offline testing but has not been integrated into the live imaging workflow. The grant application should describe the project as starting at TRL 3 and targeting TRL 6 or 7, not as a minor upgrade to an already-commercial platform.

Assessors reward honesty here. Claiming a high starting TRL for unproven work damages your credibility. Claiming a low starting TRL for work that is already well evidenced wastes the project's apparent ambition.

How funders use TRL

Most Innovate UK competitions specify an eligible starting and target TRL range. A Collaborative R&D call might want projects that start at TRL 3 and reach TRL 6. An EIC Accelerator project might need to start at TRL 5 or above and reach TRL 7 or 8. If your project sits outside the range, it is usually ineligible regardless of how good the idea is.

TRL also shapes the budget and the risk profile. Lower TRL projects need more research spend and carry higher technical risk. Higher TRL projects need more demonstration and scale-up spend, and the risk shifts towards market and manufacturing execution.

UKRI publishes a clear table of the activities associated with each TRL, which is a useful reference when you are deciding where your project honestly sits.

TRL is only half the story

A technology can reach TRL 7 and still fail because no one will pay for it. That is where Commercial Readiness Levels come in. TRL answers whether the technology can work. CRL answers whether a customer will buy it, whether the market is understood, and whether the business model is proven.

If you are preparing a grant application, state your TRL clearly and honestly, then use the rest of the application to show that the commercial readiness is rising alongside the technical readiness. We cover the commercial side in our companion article on Commercial Readiness Levels.

Sources and further reading

UKRI publishes a table of the activities typically associated with each TRL, which is the reference most UK funders follow. The Aerospace Technology Institute also provides applicant guidance on the nine-level scale. For the commercial side, see our article on Commercial Readiness Levels, which draws on the Curtinnovation Readiness Levels and KTH Innovation Readiness Level model.