What Size of Recessed Lighting Should Use? A Procurement View on Philips Lighting

A few weeks ago, one of our facilities guys called me from a ladder. He had a hole in the ceiling, a box of trims, and a question I’ve heard a hundred times: “What size of recessed lighting should use?”

I used to think that was an easy question. Six-inch downlight in a standard office. Maybe four-inch for accent. That’s what every contractor told me, and for the first two years I just signed the PO.

Then I started tracking what actually happened after installation. That’s when I realized the size question is not a spec question. It’s a cost question. And most people, including me, ask it too early in the process.

The size question is never just about inches

“What size of recessed lighting should use” is the wrong way to start a purchasing decision. The right question is: “What is the room trying to do?” A 4-inch fixture at 8 feet gives a tighter beam. A 6-inch fixture at 8 feet gives a wider, softer pool. Neither is better until you know the ceiling height, the task plane, and how many fixtures you actually need.

Here’s an example from a renovation I audited in 2024. The design called for 85 recessed fixtures. The contractor wanted 6-inch because that was what was in stock. The lighting rep suggested 5-inch with a narrow trim to reduce glare on a whiteboard wall. The difference wasn’t the fixture price. It was the layout: the 5-inch option needed 82 fixtures instead of 85, and it eliminated a “glare complaint” email thread. That’s the kind of thing I do not see on a purchase order.

Put another way: the fixture size controls how much light stays where you want it. Get it wrong, and you’ll install more fixtures, add dimmers, or call a technician back. All of those are line items.

Back in January 2025, I looked at publicly listed prices from three distributor sites for 4-inch commercial downlights. The spread between the cheapest option and a name-brand option was about $10–15. The labor to install either one was the same. So the fixture price is the wrong thing to obsess over.

Over the past six years, I’ve approved about $340,000 in lighting-related invoices. I’m not an engineer, so I can’t speak to photometric reports the way a lighting designer would. What I can tell you from a procurement perspective is that the cheapest fixture is rarely the final cost. The final cost includes the trim, the driver, the mounting frame, the electrician’s time, and the meeting where you decide why the room is too bright.

What a spotlight technician taught me about “premium”

I’ve spent a lot of time around lighting technicians. The one who changed my thinking was a spotlight technician working on a showroom project. He said something I’ll never forget:

“The fixture is just a flashlight until you set the trim and the lens. Then it becomes a tool.”

He was talking about beam angles, but the same logic applies to brand. When someone asks me for a Philips Hue alternative, I do not start with price. I ask what problem they’re trying to solve. If you need one smart lamp in a break room, a Philips Hue alternative can make sense. If you’re installing a dozen ceiling fixtures on a Zigbee network, a cheap bulb can fail in a way that costs more than the savings.

Take the Philips Hue OmniGlow as an example. I’m not going to quote its specs here, because that’s not the point. The point is that any fixture in the Hue ecosystem carries an assumption: the controller, the bulbs, and the sensors should talk to each other. That’s great if you’re installing a small set. It’s a different story when you’re scaling to 40 nodes and a facilities team that doesn’t think in Zigbee.

I’m not a lighting designer, so I can’t speak to the aesthetics of one fixture versus another. What I can say: the “premium” brand is a hedge against the cost of failure. Sometimes that hedge is worth it. Sometimes it isn’t. There is no universal best. There is only the cost of the failure you’re trying to avoid. A Philips Hue OmniGlow might be right for a client-facing space where uptime matters. For a back office with no controls requirements, a non-Philips fixture could be the better decision.

The hidden cost of smart lighting and Zigbee temperature sensors

Smart lighting is where the cost model gets messy. Most budgets include fixtures and controls. They forget sensors, commissioning time, and the person who has to reset the network on a rainy Tuesday.

One issue I keep seeing: the assumption that Zigbee stuff just works together. A Zigbee temperature sensor can make a space feel better. Pair it with the right gateway, and it can adjust color temperature through the day—4000K in the mornings, 3000K in the afternoons. That sounds nice. The problem is placement. In one office, we set up a Zigbee temperature sensor in a junction box because it was “out of sight.” It reported 6°C too high, so the lights kept dropping to 2700K during work hours. The lighting was fine. The placement was the problem.

My point is not that Zigbee is bad. My point is that adding “smart” adds a second budget. Once you accept that, you can compare systems properly: Philips Hue for smaller spaces, a commercial-grade Philips system with a dedicated network for larger floors, or a third-party system if your controls team has a strong preference. The right answer depends on who will maintain it.

If I remember correctly, the sensor cost was around $32. The investigation to find it cost more than $600 in engineering time. That’s the kind of hidden cost that never appears in a line-item quote. It appears in the invoice after the system doesn’t behave.

What happens when you skip the total cost analysis

In 2023, I audited a lighting budget for a 9,000-square-foot office. The initial quote was $27,600 for fixtures. A “value” alternative came in at $18,400. That’s a $9,200 difference. On paper, it looked like a no-brainer. But the lower quote used a different driver that didn’t support the dimming protocol already in the building. We would have had to replace 12 dimming modules at $220 each—$2,640—and the electrician quoted another $1,800 to re-run part of the control wiring. The “savings” shrank to $4,760.

I don’t know if the $18,400 fixture would have failed. What I know is that the spec did not match the system. And in procurement, a mismatch is a future invoice. So glad I asked for the compatibility list before signing. We were one approval away from a 60-fixture mistake.

There’s something satisfying about finding a genuinely better spec before you order. After a few painful retrofits, you start asking for photometric files, driver curves, and warranty terms before you compare prices. It sounds slow. It’s not. It’s the difference between a one-time quote and a five-year relationship with the ceiling.

So, what size of recessed lighting should use?

Here’s the answer I give after all that.

If you need a starting point, use 4-inch for hallways, closets, and accent walls. Use 6-inch for open office areas with 9-to-11-foot ceilings, especially if you want uniform light. But don’t order anything until you check three things:

• Ceiling height and the recommended light distribution from the fixture datasheet.
• Whether the trim, driver, and mounting frame are covered by the same warranty.
• Whether the control system—Zigbee, DALI, or 0-10V—has a validated compatibility list with the fixture.

That last one is where the smart lighting budget lives. A $30 sensor is not a problem. A $30 sensor sitting in the wrong spot on an incompatible network is a $400 investigation.

I’ll be honest about the limit of this advice: I’m a buyer, not an engineer. If you’re designing a room with high aesthetic expectations, hire a professional. If you’re making a purchasing decision, look past the “what size” question and ask the question behind it: what is the total cost of the light over the next five years?

That question will do more for your budget than any brand name. Even a brand name as strong as Philips.