Enter an LED L70 or L80 rating and operating schedule to plan a group replacement date and fixture quantity.
Advanced options
Table of contents
How to use our LED L70/L80 Useful Life and Group Replacement Calculator
- Choose the Printed light-life rating shown on the fixture cut sheet, then enter its paired Rated life in hours.
- Choose How will you enter the operating schedule? and enter either Lights on plus Lights used, or Annual operating hours from your records.
- Enter Installed or last group-replaced on, Check remaining life as of, and Fixtures in this replacement group.
- Set Replace group at to match your maintenance policy, then select Calculate.
- Sanity-check Estimated annual operating hours against a timeclock, control schedule, or building management system record before using the planned date for a budget or purchase order.
Definitions
L70: A lumen-maintenance rating meaning the LED light source is rated to have 70% of its initial light output at the listed rated hours. [1]
L80: A lumen-maintenance rating meaning the LED light source is rated to have 80% of its initial light output at the listed rated hours. [2]
Rated life: The published operating-hour value paired with L70 or L80. It is not automatically a full-fixture failure date.
Group replacement trigger: The chosen percent of Rated life when the matching fixture group is planned for replacement. It is separate from L70 or L80.
Annual operating hours: The estimated hours the lights operate in one year, entered directly or calculated from daily hours, days per week, and 52 weeks.
Common mistakes and quick fixes
Mistake: Treating Printed light-life rating L70 as a rule to replace the group at 70% of its rated hours.
Fix: Choose the printed L70 or L80 value, then set Replace group at separately to your maintenance policy.
Mistake: Entering a warranty length as Rated life.
Fix: Copy the hour value paired with L70 or L80 on the cut sheet, label, submittal, or TM-21 report.
Mistake: Counting open business hours instead of actual Lights on time.
Fix: Include overnight operation, cleaning shifts, and control schedules when entering Lights on and Lights used.
Mistake: Using the installation date as Check remaining life as of.
Fix: Enter the review or inspection date for Check remaining life as of, and keep Installed or last group-replaced on as the plan start date.
Mistake: Combining different fixture models in Fixtures in this replacement group.
Fix: Make a separate plan for fixtures with a different Rated life, schedule, start date, or replacement policy.
Limitations & Key Assumptions / Boundary Conditions
- The plan assumes the entered annual operating schedule stays representative. Seasonal closures, occupancy changes, controls, and 24-hour operation can move the date.
- Rated L70 and L80 describe light output remaining at rated hours. They do not predict when drivers, controls, housings, or every fixture will fail.
- The calculator does not convert an L70 rating to L80, or an L80 rating to L70. Use the rating published for the fixture.
- Remaining operating hours are estimated from calendar time and the annual schedule, not measured from an hour meter.
- Replacement quantity equals Fixtures in this replacement group and assumes one replacement unit per fixture. Lamps or modules per fixture are not included.
- The planned date is a maintenance target, not a warranty determination or a predicted failure date.
Methodology
Calculation method
The calculator first finds annual operating hours from the active schedule entry method. It then applies the separate group replacement trigger to the printed rated life. L70 or L80 only determines the light-output explanation; it does not change the trigger-hour calculation.
annual operating hours = lights on per day * lights used per week * 52
planned trigger hours = rated life * replace group at / 100
planned calendar years = planned trigger hours / annual operating hours
The planned calendar time is added to Installed or last group-replaced on. Whole anniversaries are added first, then the remaining fraction is calculated from the actual days between surrounding anniversaries. The date is rounded up to the first full day when the trigger is reached. Date-only arithmetic is used so daylight-saving changes do not move the result.
estimated hours used = elapsed calendar years * annual operating hours
remaining operating hours = planned trigger hours - estimated hours used
remaining calendar years = remaining operating hours / annual operating hours
Worked example
For an L70 rating of 50,000 hours, a group trigger of 80%, and 5,000 annual operating hours, the trigger is 40,000 operating hours. That equals 8 calendar years. If the group started on January 1, 2020 and is reviewed on January 1, 2025, about 25,000 hours are used and 15,000 hours, or 3 years, remain. The planned group quantity is exactly the entered fixture count.