What a Commercial LED Retrofit Involves: From Walk-Through to Final Inspection
The steps, the decisions in each one, and what moves the schedule and the cost.
Written October 5, 2026 by ThreeCo.
An LED retrofit replaces the fluorescent, metal halide or high-pressure sodium lighting in a commercial building with LED. From the outside it looks like a fixture swap. In practice it is a short sequence of decisions — what to replace, with what, how to control it, and when to do it — and most of the difference between a good retrofit and a disappointing one is made before a single fixture comes down.
This is how ThreeCo runs one, step by step, with the things that change the timeline and the cost called out as they come up. It is the same process whether the building is a small office or a credit union headquarters with around 400 recessed can lights.
Step 1: the walk-through
We walk the building, count and identify the existing fixtures, and note the spaces that need more or less light than they have. The count matters for two reasons: it sets the scope of the quote, and where a utility rebate is in play, the incentive is paid per fixture against what was there before.
A full lighting audit with a photometric layout is available on request. It is not part of every quote. It earns its place when the layout itself is changing — a warehouse being re-racked, an open office replacing a cubicle floor, a parking lot with dark spots — rather than when the same fixtures are being replaced in the same places.
Step 2: design and fixture selection
Bob DeFries, our CEO, specifies the replacement fixtures and the controls; his background is in electrical engineering and architectural design. You get a written quote for the fixture list, the controls and the labor.
The biggest choice in this step is how much of each old fixture to keep. There are three broad options, and a building often uses more than one:
- LED tubes in the existing fixture. Some tubes run on the existing ballast, which is quick but leaves an old ballast in the circuit to fail later. Others bypass the ballast and are wired directly, which removes it but means the fixture is rewired.
- A retrofit kit. The fixture housing stays in the ceiling and everything inside it is replaced with an LED assembly. Less ceiling disruption than a new fixture, and no old ballast left behind.
- A new LED fixture. The old one comes out entirely. The most work per fixture, and the right answer when housings are damaged, the layout is changing, or the old fixture is simply the wrong type for the space.
What we retrofit
Interior troffers, recessed can lights and high-bay fixtures; exterior wall packs, canopy lighting and parking lot poles. Interior and exterior work can be quoted together, which is useful because the exterior is where old metal halide and high-pressure sodium fixtures tend to survive longest.
Step 3: the install
We schedule the install with you, then a crew led by Master Electrician Jason Strange swaps the fixtures, fits the controls and handles any wiring the new fixtures need. In an occupied building the work is usually sequenced area by area so the rest of the building keeps running.
Old lamps and ballasts have to go somewhere. Fluorescent lamps contain mercury and need to be disposed of properly rather than thrown in a dumpster, and some older ballasts contain PCBs. Both are part of planning the job, not an afterthought at the end of it.
Step 4: controls and commissioning
Occupancy sensors, dimming and scheduling are wired, programmed and tested before we leave. A retrofit is the right moment to add them, because the ceiling is already open and the crew is already there. Controls that are installed but never set up save nothing, which is why commissioning is a step of its own and not a line on the punch list.
Permits and the final inspection
Depending on the city, replacing fixtures and adding lighting controls in a commercial building can require an electrical permit, and a permit means an inspection before the job is closed out. Rules differ between cities in the metro, so this is checked for each building rather than assumed.
In plain terms, the inspector is checking that the work is safe and to code: that new fixtures and any rewired ones are connected and supported properly, that circuits are protected correctly, and that the controls do what the plans say. A retrofit designed to the rules from the start is designed to pass on the first visit.
What sets the timeline
We quote a schedule with the price. The things that move it, roughly in order of how often they matter:
- Fixture count, and how many different fixture types there are.
- Ceiling height and access. A high-bay warehouse needs a lift; a drop ceiling over desks does not.
- Whether the building is occupied, and how the work has to be sequenced around the people in it.
- Lead times on the fixtures and controls chosen.
- How much controls work is in scope.
- Utility pre-approval, where a rebate program is open and the project is large enough to need it before equipment is ordered.
What changes the cost
Every retrofit is quoted from the walk-through, and we do not publish prices because two buildings with the same fixture count can be very different jobs. These are the factors that make the difference:
- Fixture count and fixture type.
- Tubes, retrofit kits or new fixtures — and the mix between them.
- Ceiling height and the equipment needed to reach it.
- The controls: none, occupancy sensors, or full dimming and scheduling.
- The condition of the existing wiring, and how much rewiring the new fixtures need.
- Whether the work has to happen outside the building's working hours.
- Proper disposal of the old lamps and ballasts.
The warranty
One year on workmanship, five years on materials, on every retrofit.
FAQ
Common questions
How long does a commercial LED retrofit take?
It depends on the fixture count, the ceiling height, whether the building is occupied, and fixture lead times. We quote a schedule with the price after the walk-through.
Should I use LED tubes, retrofit kits or new fixtures?
It depends on the condition of the existing fixtures and whether the layout is changing. Tubes are the least work, kits replace everything but the housing, and new fixtures replace the lot. Many buildings end up with a mix; the walk-through decides it.
Do I need a lighting audit?
Not always. A full lighting audit with a photometric layout is available on request; it is not part of every quote. It is most useful when the layout or the use of the space is changing.
Does a retrofit need a permit?
Depending on the city, fixture replacement and lighting controls work in a commercial building can require an electrical permit and an inspection. We check the rules for each building.
Is there a warranty?
Yes. One year on workmanship, five years on materials.
How do I get a number for my building?
Start with Watt, the chat button on this page. Tell it the building and roughly how many fixtures, and it goes straight to the team. You can also call (816) 730-9100.
Thinking about a retrofit?
Tell Watt the building and a rough fixture count. We'll walk it and come back with a real number.
New customers: start with Watt and get 10% off your first job.