LM-79 Testing Explained: Winning Government Tenders With NABL Lab Reports

LED lighting products are increasingly evaluated on measurable performance rather than manufacturer claims alone. For manufacturers, importers, lighting brands and project suppliers, reliable photometric and electrical data can be important for product development, technical submissions, tenders and market-access requirements.

ANSI/IES LM-79-24 is the current IES approved method for measuring the electrical and photometric performance of solid-state lighting (SSL) products. It provides procedures for reproducible measurements of parameters such as luminous flux, electrical power, system efficacy, optical distribution, colour characteristics and spectrum under specified test conditions. The 2024 edition replaced the earlier LM-79-19 edition and includes updated guidance, including changes related to spectral testing and reporting.

What is LM-79 Testing?

LM-79 is a test method, not a certification or licence. It is used to measure the performance of a complete solid-state lighting product under controlled conditions.

The method can be used for suitable LED lamps, luminaires and other SSL products intended for illumination. Instead of evaluating only an individual LED component, LM-79 focuses on the performance of the finished lighting product as a system. This makes the results useful when the interaction between the LED source, driver, optics and complete luminaire affects the final light output.

A properly prepared LM-79 test report can therefore provide objective performance data that can be compared with a product specification, project requirement or tender clause.

What is New in ANSI/IES LM-79-24?

For organisations still referring to older LM-79-08 or LM-79-19 reports, the current reference should be checked carefully.

ANSI/IES LM-79-24 was published by the Illuminating Engineering Society in 2024. The latest edition updates the test method and reporting guidance and includes changes involving airflow considerations, power-supply resistance and inductance dependency, spectral testing and the test-report outline.

When a buyer, tender authority or project specification asks for LM-79 testing, the requested edition should be confirmed before testing. A laboratory report prepared to an older edition should not automatically be treated as equivalent to a report requested against LM-79-24.

What Parameters Are Measured Under LM-79?

The exact report format and measurements depend on the applicable test programme, but LM-79 covers major electrical, photometric and colour-related measurements.

1. Total Luminous Flux

Total luminous flux expresses the overall light output of the SSL product, normally reported in lumens. It helps establish how much light the complete product actually produces under the stated test conditions.

2. Electrical Power

The test method includes measurement of the electrical power consumed by the product during operation. This allows the electrical input to be considered alongside the measured light output.

3. System Efficacy

System efficacy expresses light output in relation to electrical power, commonly reported as lumens per watt. It is a useful performance metric for comparing lighting products and checking whether declared efficiency values are supported by laboratory measurements.

4. Luminous or Optical Distribution

LM-79 includes procedures for measuring luminous, radiant or photon intensity distribution, where applicable. Distribution data is particularly relevant for luminaires whose performance depends on beam direction, optical design or application-specific light placement.

5. Colour and Chromaticity

The method includes measurement of colour quantities and spectrum for applicable SSL products. Depending on the laboratory test programme, reports may contain parameters such as chromaticity coordinates, correlated colour temperature and colour-rendering-related information. The exact parameters should be confirmed with the laboratory and the purchasing specification.

6. Measurement Uncertainty

LM-79-24 includes specific provisions for measurement uncertainty and reporting. This is important because a useful laboratory result should communicate not only measured values but also the associated measurement information required by the method.

Which LED Products Can Be Evaluated?

LM-79 is intended for appropriate solid-state lighting products used for illumination. Depending on the product and project requirement, testing may be relevant to:

• LED lamps and replacement lamps
• LED indoor luminaires
• LED panels and downlights
• LED street and roadway luminaires
• LED floodlights
• LED high-bay and industrial luminaires
• architectural and decorative SSL products
• emergency or other specialised SSL luminaires
• selected integrated solar LED lighting products

Applicability should always be confirmed against the product construction, intended use, applicable standard and purchaser or tender specification. LM-79 should not be presented as a blanket mandatory requirement for every LED product.

Why Are LM-79 Reports Requested in Tenders?

Many lighting procurement documents use laboratory performance data to establish technical specifications and verify supplier declarations. However, there is no single universal rule that every government or private tender must accept or demand the same LM-79 report.

A tender may specify requirements relating to photometric performance, laboratory accreditation, report age, product model identification, test standard or particular measured parameters. Some tenders may specifically name LM-79, while others may reference an Indian Standard, project specification or another recognised measurement requirement.

For this reason, suppliers should read the tender's technical schedule before arranging testing.

What to Check in a Tender

Before submitting an LM-79 report, check:

1. Whether LM-79 is specifically named.
2. Which edition of the method is required.
3. Whether the report must come from a NABL-accredited laboratory or another specified laboratory arrangement.
4. Whether the laboratory's accreditation scope covers the relevant testing activity.
5. Whether the report must identify the exact model, rating and configuration offered in the bid.
6. Whether there is a maximum report age or retest requirement.
7. Whether specific values such as lumen output, efficacy, CCT, colour information, power or distribution are specified.
8. Whether sample photographs, product datasheets, calibration information or declaration documents must accompany the report.

This approach reduces the risk of obtaining a technically valid report that does not satisfy the tender's documentary requirements.

Is a NABL LM-79 Report Required?

A key distinction is important here: NABL accredits laboratories; it does not issue an LM-79 product certificate.

NABL provides accreditation for testing laboratories under ISO/IEC 17025 and maintains an accreditation system intended to support confidence in testing and calibration results. NABL also publishes laboratory accreditation information and scopes.

Therefore, when a purchaser asks for a “NABL LM-79 report,” the practical requirement is generally a test report issued by a laboratory whose accreditation and scope are appropriate to the requested testing.

Do not rely only on the presence of a NABL logo. Check the laboratory's current accreditation status and, importantly, the scope of accreditation relevant to the required test.

LM-79 Testing Equipment

Two important laboratory measurement approaches associated with LM-79 work are integrating-sphere measurements and goniophotometric measurements.

An integrating sphere is used for measurements such as total luminous flux and relevant spectral or colour quantities.

A goniophotometer is used to determine angular light-distribution characteristics where required.

The equipment, environmental conditions, electrical conditions and test preparation need to be controlled according to the applicable method. LM-79-24 specifically addresses physical and environmental test conditions, electrical test conditions, preparation, measurement uncertainty and reporting.

LM-79 vs LM-80 vs TM-21

These terms are often used together in LED documentation, but they serve different purposes.

LM-79 evaluates the electrical and photometric performance of an SSL product under specified conditions.

LM-80 addresses maintenance of light-output characteristics of solid-state light sources such as LED packages, arrays or modules. It is not the same as complete luminaire performance testing.

TM-21 is associated with projecting lumen maintenance from LM-80 data. Therefore, LM-79, LM-80 and TM-21 should not be treated as interchangeable documents.

An LM-79 report also should not be described as a lifetime test. LM-79 provides performance measurements at specified conditions; it does not by itself establish the product's long-term lifetime or lumen-maintenance rating.

What Should an LM-79 Test Report Include?

Before using a report for a tender, certification file or customer submission, review whether it clearly identifies:

• Manufacturer and product name
• Exact model or model family
• Product configuration and electrical rating
• Test standard and edition
• Test date
• Laboratory identification
• Applicable accreditation information
• Operating and environmental test conditions
• Measured electrical values
• Total luminous flux
• System efficacy
• Applicable colour and chromaticity data
• Applicable intensity or distribution data
• Measurement uncertainty
• Required test and reporting information under the selected method

The report should correspond to the actual product configuration being offered. A report for a different driver, LED package, optics arrangement or model should not automatically be treated as evidence for another configuration.

Common Reasons for LM-79 Report Problems

Reports can become difficult to use when the tested sample does not match the offered model, the requested test edition is unclear, the laboratory scope is not checked, or the report does not contain information required by the tender.

Another common mistake is assuming that an LM-79 report automatically proves every aspect of product compliance. It does not. Depending on the product and market, additional safety, EMC, environmental, ingress-protection, performance or regulatory testing may be required.

Does Your LED Product Need LM-79 Testing?

The answer depends on what you are selling, where it will be used, and what specification applies.

For a tender, begin with the technical qualification clause. For a regulatory programme, check the applicable current scheme or standard. For a customer requirement, review the customer's exact testing specification.

This is more reliable than treating LM-79 as a universal certification requirement for all LED products.

Get Support for LM-79 Testing

Instacertify helps manufacturers, importers and lighting suppliers coordinate LM-79 testing, review applicable requirements, identify suitable laboratory documentation and organise report-related compliance support.

Before testing begins, we can help map your product against the required specification so that the selected report is aligned with the intended use.

For LM-79 testing support, contact Instacertify Labs Private Limited and share your product model, datasheet and tender or project requirement.

Need help with LM-79 testing or an accredited laboratory report? Contact Instacertify for product-specific guidance and testing coordination.