Years to Hours

A Datasheet Promises Hours; a Replacement Plan Needs Dates

Manufacturers rate equipment in operating hours because that is what wears it out. An LED module is quoted at 50,000 hours to L70, a motor bearing at 40,000 hours to L10, a compressor at a comparable figure buried in a service manual. Budgets, warranties and replacement programmes run on calendar years instead. Getting from one to the other takes exactly one extra piece of information that the datasheet never supplies: how many hours a year the thing will actually run.

Conversion factor: 1 yr = 8 765.82 h here, the Gregorian mean of 365.2425 days × 24. A 50,000-hour rating is therefore 5.70 years of unbroken 24/7 running — but on an office schedule of 10 h × 5 days, 2,608.88 h a year, the same fitting is rated for 19.2 years.

What the Rating Does and Does Not Say

It is a population statistic

L70B50 means half of a tested batch is still above 70 % of its original output at that hour count. It is a forecast about a fleet, never a guarantee about the one unit above your desk.

Duty cycle is the missing variable

The same part can be rated at four years or twenty-four depending only on annual running hours. Any replacement date quoted without the duty assumption beside it is not checkable.

Two different years are in circulation

Datasheets almost always assume 8,760 h — 365 flat days. This converter uses 8,765.82, the leap-adjusted mean. The 5.82-hour gap is negligible per year and still under 150 h across a 25-year horizon.

Heat moves the number more than hours do

Ratings are quoted at a stated case temperature and ambient. Run the same part hotter, in a sealed enclosure or a plant room, and the rated hours arrive early no matter how carefully the years were calculated.

Turning a Rated Figure Into a Replacement Year

The workflow below produces a defensible replacement date rather than a round number somebody guessed in a meeting.

Convert your intended service life to hours

Enter the years the asset is expected to stay in place — 5, 10, 15 — and read the hours. This is the 24/7 ceiling: no part running continuously can reach that year figure unless its rating exceeds the number shown.

Scale it by the real duty cycle

Multiply the hours by the fraction of the time the equipment actually runs. An office schedule is roughly 30 % of the clock, a cooling season perhaps 17 %, a process plant close to 100 %. Compare that against the rated hours.

Reverse it once you have the rating

Press swap (↔) for h → yr and drop the datasheet number straight in. 60,000 h reads as 6.84 yr of continuous duty — the shortest possible calendar life, before any allowance for downtime.

Copy the figure into the asset register

The copy control gives the plain number without units or separators, which is what a CMMS import file or a depreciation schedule expects. Ctrl + C in the field does the same.

Fixed-length years: the year here is always 365.2425 days, so leap years are averaged in rather than counted individually. For a warranty that expires on a named date, work from the calendar; for a service interval, the average is the right tool.

Rated Hours Against the Duty Cycles They Meet

Six ratings taken at their common published values, each divided by a representative annual running time. The right-hand column is the calendar life that combination implies.

Equipment and rating	Rated hours	Operating hours a year	Rated life in years
Household LED lamp, L70B50	25 000 h	3 h a day → 1 095.73	22.8 yr
Office LED panel, L70	50 000 h	10 h × 5 days → 2 608.88	19.2 yr
Street lantern, dusk-to-dawn	100 000 h	≈ 4 100	24.4 yr
Motor bearing, L10 basic rating life	40 000 h	Continuous → 8 765.82	4.6 yr
Residential AC compressor	30 000 h	Cooling season → 1 500	20.0 yr
Rack cooling fan	60 000 h	Continuous → 8 765.82	6.8 yr

The two continuous-duty rows are the ones that catch people out. A bearing rated at 40,000 hours sounds generous until it is spun without pause, at which point it is a four-and-a-half-year part — shorter than a lamp with half the rating that only works three hours an evening. Ratings can only be compared after both have been divided by their duty.

What This Pair Does While an Asset Register Is Built

Test a supplier's life claim on the spot

Typing the claimed years shows the hours they imply at continuous duty, so a "25-year" fitting can be checked against its own rated hour count while the sales call is still running.

Datasheet hours read back as years

Swapping the direction takes 40,000 or 100,000 straight off the specification sheet and returns the minimum calendar life the rating can support.

Decades for long-horizon assets

Both dropdowns carry every unit in the app, decades and centuries included, which suits infrastructure written down over forty years rather than five.

Six-figure hour counts stay readable

Thousands are separated in the output, so 219 145.5 h for a twenty-five-year horizon is transcribed into the asset register correctly the first time.

Questions Raised When a Replacement Budget Is Set

What does L70 on an LED datasheet actually promise?

That the light output has fallen to 70 % of its initial value by the stated hour count — dimming, not failure. The letter pair matters: L70B50 says half the tested sample is expected to be at or above that level, while L90B10 is a much stricter claim, 90 % output with only one unit in ten falling short. Retail lamps are usually quoted at L70B50, which is why a room can feel visibly duller years before anything stops working. Choose the replacement trigger on the L and B figures, not on the headline hour count alone.

Why does one 50,000-hour rating mean 5.7 years in one building and 19 in another?

Because the rating counts operating hours and the building sets how many of them happen a year. A data hall runs 8,765.82 a year; an office on 10 h × 5 days runs 2,608.88; a school with holidays perhaps 1,900; a stairwell on a sensor a few hundred. Same part, four different replacement dates. It is also why occupancy sensors and daylight dimming pay back twice — they cut energy now and stretch the rated life into later budget years, which is often the larger saving on a big estate.

Is bearing L10 life the same kind of number as LED L70?

Both are population statistics, but they describe opposite things. L10 is the life that 90 % of identical bearings will reach or exceed under a stated load before fatigue failure — an end, not a fade. It is also load-dependent in a way LED ratings are not: for ball bearings the basic rating life varies with the cube of the load ratio, so halving the load multiplies the rated hours by eight. A 40,000-hour L10 quoted for one duty says nothing about the same bearing on a heavier shaft, whereas an LED's rated hours move mainly with drive current and temperature.

How much does running hot cut into rated hours?

Enough to dominate the arithmetic. The rule of thumb for electrolytic capacitors — usually the first thing to die in an LED driver or a power supply — is that life doubles for every 10 °C the operating temperature drops, and halves for every 10 °C it rises. A driver rated 60,000 hours at 65 °C is a 30,000-hour part at 75 °C, which turns 6.8 years of continuous duty into 3.4. Lubricant life in a bearing behaves similarly. When a rated life is missed by half, poor ventilation is a better first suspect than a bad batch.

When is it worth replacing a whole fleet instead of failures as they appear?

When access costs more than the part. Group replacement is normally scheduled at around 60–70 % of rated life, before the failure curve steepens, and it wins wherever a visit needs scaffolding, a lift, a road closure or a production stop — high-bay lighting, street lanterns, anything in a ceiling void. Spot replacement wins where a unit can be swapped from a step-ladder in two minutes. Do the sum in hours per year rather than in years: an estate running its lamps 4,100 hours a year reaches the same trigger point in a third of the calendar time as one running them 1,100, and the maintenance budget has to be phased accordingly.