Most LED high bay lighting projects get approved on a payback figure somebody produced in ten minutes on a spreadsheet. 
Half of those figures are wrong, usually optimistic, and the gap shows up a year later when the utility bill hasn’t moved the way finance was told it would.
The work that produces a defensible number is not complicated. It just has to actually be done before the order goes in.
Survey what’s there first
Walk the building and record four things per fixture type: what it is, how many there are, what it draws including ballast losses, and how many hours it runs.
That last one is where estimates go wrong most often. People assume single-shift operation, 2,000 hours a year. Then it turns out the aisle lights never go off because the switch is behind a locked panel, and actual run time is closer to 6,000 hours. That triples the saving and changes the whole business case.
Put a logger on a representative circuit for two weeks if you can. It costs almost nothing and it replaces the biggest guess in the calculation with a measurement.
While you are up there, note the ceiling height at the lowest and highest points, the mounting method, and whether the existing positions are on a sensible grid. Old metal halide layouts were often spaced for a different beam pattern and copying them one-for-one is how you end up with dark aisles.
Check what the utility will pay
Rebates change the arithmetic more than anything else in the project. Most US utility programmes require a DLC listing as a condition of payment, and many pay a higher rate for DLC Premium products than DLC Standard.
Rebates are typically structured one of two ways: a fixed amount per fixture, or a rate per watt reduced. The per-watt structure rewards replacing the largest existing fixtures first, which is worth knowing when you phase the work.
Two things to check before ordering: that the specific model number appears on the DLC qualified products list, and whether your programme requires pre-approval. Buying first and applying later disqualifies you under a lot of programmes.
Phase it in the right order
If the budget won’t cover the whole building at once, sequence by run hours rather than by area.
The fixtures that run 6,000 hours a year pay back in a fraction of the time of the ones that run 1,500, even though they cost the same to replace. Doing the high-hours zones first generates savings that help fund the rest. It also means the areas people complain about most get fixed first, which does more for the project’s internal reputation than an even sweep across the site.
Our LED high bay lighting for phased warehouse retrofits covers the common wattages, so matching later phases to the first one is straightforward.
Work out the payback honestly
The four inputs:
- Energy saved. (Old watts minus new watts) × hours × kWh rate. Use the real ballast draw for the old fixtures, not the lamp rating.
- Maintenance saved. Lamp cost plus labour plus lift hire, divided by the replacement interval. In high-ceiling spaces this is often 30 to 40 percent of the total saving and it routinely gets left out.
- Install cost. Fixtures, labour, disposal of the old units, and any lift access.
- Deducted from install cost.
A typical warehouse retrofit lands somewhere between 18 months and three years. Anything claiming under twelve months is usually assuming run hours nobody verified, or leaving out install labour.
Add demand charge savings if your tariff has them, but calculate rather than estimate — lighting rarely coincides with a facility’s demand peak, so the reduction is often smaller than the energy saving suggests.
Plan the controls at the same time
Retrofitting sensors later means going back up with a lift, and the access cost is most of the job. Decide the control strategy while the lift is already booked.
For most high bay spaces that means occupancy sensing with bi-level dimming, plus daylight response near skylights and roll-up doors. Set hold times realistically — 15 minutes in a picking aisle, 5 in a rarely used storage bay. Aggressive settings look better on paper and get overridden by staff within a fortnight.
Frequently Asked Questions
How long does an LED high bay lighting retrofit take?
A crew of two typically changes out 25 to 40 fixtures a day depending on ceiling height and lift access. A 200-fixture warehouse is usually a week to ten days, and most of it can be done outside production hours if disruption is a concern.
Do I need a photometric layout?
For a straight one-for-one swap at similar output, usually not. For anything that changes fixture positions, spacing or beam angle, yes — it takes a supplier an hour and it is the only reliable way to know whether the aisles will be evenly lit before you commit.
Will LED high bay lighting work on my existing circuits?
Almost always, and you will have spare capacity afterwards since the new load is a fraction of the old. Confirm voltage compatibility — most commercial high bays accept 120-277V, but 480V sites need fixtures rated for it.
How much can LED high bay lighting reduce energy use?
Fixture-for-fixture, 55 to 70 percent against metal halide. Add occupancy and daylight controls and total reductions of 75 to 85 percent are realistic in spaces that are not continuously occupied.
