How to Read an LED Spec Sheet: Lumens, Efficacy, L70 and Listings

Two fixtures can look the same in a product photo and still behave very differently on the job. The spec sheet is where the real differences show up. Here is how to read one in a few minutes, line by line, so you can compare fixtures fairly and catch problems before they hit your bid.

Start with delivered lumens, not wattage

Wattage tells you what the fixture draws. Lumens tell you how much light it puts out. When you replace an old fixture, match the light, then pick the lowest wattage that gets you there.

Make sure the lumen number is for the whole fixture. Some sheets list the lumens of the LED chips alone, which is always higher than what actually leaves the lens. The number you want comes from a complete fixture test, often labeled as delivered or luminaire lumens, and usually backed by an LM-79 test report. LM-79 is the IES method for measuring the light output, power and color of a complete LED fixture.

Selectable fixtures list one lumen value for each wattage setting. Read the row for the setting you plan to use, not the top of the range.

Efficacy: lumens per watt

Efficacy is lumens divided by watts. It is the fastest way to compare two fixtures that do the same job. You can check it yourself. The EDIPAI G4 4ft strip with no sensor base, for example, is listed at 60W and 10,020 lumens. Divide 10,020 by 60 and you get 167 lumens per watt.

Color: CCT and CRI

CCT, measured in Kelvin, is how warm or cool the light looks. 3000K reads warm, 4000K neutral and 5000K cool white. Many commercial fixtures now let you pick CCT with a switch on the fixture, so one SKU covers several jobs. Our color temperature guide covers which to use where.

CRI is how accurately colors show up under the light, on a scale up to 100. Most commercial fixtures list 80 or higher. Retail, healthcare and some offices may call for 90 or above, so check the spec for the space.

Rated life: L70 and where it comes from

LEDs rarely burn out. They slowly get dimmer. L70 is the number of hours until the fixture is expected to put out 70% of its starting light. That is the point most people treat as the end of useful life.

The L70 number on a sheet is a projection, not a measurement. The LED chips are tested under a method called LM-80, and the results are projected forward using a method called TM-21. TM-21 limits how far the projection can go: no more than six times the length of the test data. A 6,000 hour test supports a projection of up to 36,000 hours. When a sheet lists a very long life, it is fair to ask what test it is based on.

Electrical: voltage, power factor and THD

Line on the sheet	What to check
Input voltage	120-277V covers most buildings. Plants and big warehouses often run 277-480V, which needs a fixture rated for it. See picking the right voltage.
Power factor	Closer to 1 is better. DLC's technical requirements call for at least 0.9.
THD	Total harmonic distortion. Lower is better, and DLC sets a limit of 20% or less.
Dimming	Most commercial fixtures use 0-10V. Residential style downlights may use Triac. They are not interchangeable. See 0-10V dimming explained.
Surge protection	Listed in kV. Matters most outdoors and on poles, where lightning and utility surges are common.

Listings and ratings

• UL or ETL. Both are nationally recognized testing labs that test to the same safety standards, and inspectors generally treat them the same.
• DLC. This is what most utility rebate programs check. The listing is tied to specific model numbers, so confirm the exact model on the DLC Qualified Products List rather than trusting a logo. Our DLC guide explains Standard vs Premium.
• Damp, wet or IP rating. Damp is fine for covered areas. Wet is for places where water hits the fixture directly. See wet, damp and IP ratings.
• Operating temperature. The ambient range the fixture is rated for. Critical for freezers, unheated buildings and hot ceilings over ovens or furnaces.

Outdoor extras: distribution and BUG rating

Area lights and wall packs list a distribution type, such as Type III or Type V. That describes the shape of the light on the ground and drives your pole spacing. Our parking lot guide walks through it.

Many outdoor sheets also list a BUG rating, which stands for Backlight, Uplight and Glare. Each gets a score from 0 to 5, where lower means less stray light. Towns with dark sky or light trespass rules often set a maximum BUG rating, so check local code before you order.

Warranty and the fine print

Read what the warranty covers and for how long. Check whether it applies to the whole fixture or only the LEDs, and whether it requires the fixture to be run inside its rated temperature range. Also look at what ships in the box. Sensors, mounting brackets, photocells and emergency battery packs are sometimes standard and sometimes sold separately as accessories.

A quick checklist before you order

• Delivered lumens at the wattage setting you will actually use.
• Efficacy that matches your own lumens divided by watts.
• CCT and CRI that fit the space.
• Voltage that matches the building.
• The exact model number on the DLC list if you are claiming a rebate.
• The right location rating and temperature range.
• Mounting hardware and controls, included or ordered separately.

Every product page on our site links the manufacturer spec sheet when one is published. Browse high bays, panels and center baskets or area lights, or start from all fixtures and compare side by side. Questions on a spec sheet? Contact us.