Aluminum vs PC Downlight Housing: A Material Guide for B2B Buyers
"Same shape, same cut-out, 40% cheaper" — that is how a PC (polycarbonate) housing usually enters the conversation. Sometimes it is the right call. Sometimes it is a warranty claim waiting for its first summer. The difference is not opinion; it is thermal physics plus a bit of honest arithmetic. This guide gives you the numbers we quote from, the failure modes we see in returned goods, and a simple decision rule you can apply to your own range.
The one property that decides most of the argument
An LED does not fail because it gets old; it fails because it gets hot. Every 10°C rise at the LED junction roughly halves the rate at which the phosphor and chip age gracefully. The housing is the only path that heat has to the room, so the housing material is the thermal design. Compare the two candidates:
| Property | Die-cast aluminum (ADC12) | PC (polycarbonate) |
|---|---|---|
| Thermal conductivity | ~150–170 W/m·K | ~0.2 W/m·K |
| Heat role in the fitting | Active heat sink | Thermal insulator |
| Continuous service temperature | >200°C (coating-limited) | ~115–125°C |
| Typical unit cost (same shape) | Baseline | 30–45% lower |
| Tooling cost (same part) | Lower die cost | Higher injection mould cost |
| Weight | Heavier (feels premium) | Lighter (cheaper freight) |
| UV / outdoor behaviour | Stable with powder coat | Yellows without UV stabiliser |
Read the first two rows again. Aluminum conducts heat roughly 750 times better than PC. A die-cast body is not just a shell — it is the heat sink. A PC body is a box around a heat problem that something else has to solve.
What that means in lumen maintenance, not theory
Take a typical 12W COB downlight. On a well-designed ADC12 housing of adequate wall thickness, the solder-point temperature stabilises in the 60–75°C band in a 25°C room. Move the same light engine into a PC shell with only a small internal aluminum heat spreader, and that number climbs into the 90–105°C band. Project both against an LM-80 curve and the difference is not subtle: the aluminum version comfortably supports an L70 rating of 36,000–50,000 hours, while the PC version is struggling to honestly claim 15,000–20,000. If your sales literature says "50,000 hours" on a PC housing above 7W, your literature and your physics are in disagreement — and the customer finds out in year two.
Where PC genuinely wins
None of this makes PC a bad material. It makes it a bounded one. PC housings are a rational choice when all of the following are true:
- Wattage is low — roughly 3–5W residential fittings, where total heat load is small and a modest internal spreader copes.
- Volume is high — the injection mould costs more than a die-casting die, so the unit-price advantage only survives amortisation at scale; think tens of thousands, not a 1,000-piece trial.
- Weight drives cost — for air-freighted, high-volume residential programmes, shaving 60–80 grams per fitting is real money across a container's worth of cartons.
- The channel is DIY/retail — where the replacement cycle is accepted and nobody signs a 5-year performance warranty.
The failure modes we actually see
When PC housings come back, it is almost always one of these three, and all of them trace to heat:
- Yellowing around the light engine — the plastic closest to the heat source discolours first; on a white trim it reads as a stain the end customer assumes is a defect (it is).
- Embrittlement and cracking — plasticisers migrate out under sustained heat; spring clips and trim edges snap during re-lamping, typically in months 12–24.
- Deformation at the trim seat — the ceiling-facing edge warps, the fitting no longer sits flush, and a whole hotel corridor suddenly needs snagging.
Aluminum's failures are different and mostly cosmetic: coating chips from rough handling, or colour drift between batches — annoying, but visible before installation, not after. That asymmetry matters: a defect you catch at goods-in costs you a phone call; a defect the end user catches on the ceiling costs you the account.
The arithmetic buyers should run
The 30–45% unit saving on PC is real but incomplete. Run the full line: add the higher tooling amortisation unless your volumes are genuinely large; add the freight saving from lower weight if you air-ship; then subtract the expected cost of early-life failures at your channel's return rate. For commercial projects with 3–5 year warranties, one site revisit typically erases the saving on several hundred fittings. For a 3W retail downlight selling by the hundred-thousand, PC's maths usually wins honestly.
How to specify either one correctly
If you choose die-cast aluminum, state the alloy (ADC12 is the workhorse), minimum wall thickness at the heat-path ribs, powder-coating thickness (we check 60–80μm) and the colour standard per batch. If you choose PC, state the resin grade (UV-stabilised, flame-retardant V-0 at minimum), demand the LM-80-based temperature simulation for your exact light engine, and put a maximum solder-point temperature on the drawing as an acceptance criterion. In both cases the sentence that protects you is the same: material and thermal performance are acceptance criteria, verified on the approved sample, not descriptions.
Our short answer
For commercial downlights from 7W upward — hotels, offices, retail, anywhere with a warranty and a reputation attached — die-cast aluminum, every time. For the 3–5W residential tail of a range at genuine volume, PC is a legitimate cost play if the resin is specified and the thermal design is proven on the approved sample. We manufacture both, and we will tell you which one your wattage and warranty terms actually justify — including when the honest answer is the cheaper one. See our surface mounted housings, architectural spotlights and panel light frames for die-cast examples, and our OEM / ODM page for how we handle mixed-material ranges.
Frequently asked questions
Is aluminum or PC better for downlight housings?
For most commercial downlights above roughly 7W, die-cast aluminum is the safer choice: its thermal conductivity (around 150–170 W/m·K for ADC12) keeps LED junction temperature low, which directly extends lumen maintenance life. PC housings are acceptable for low-wattage (3–5W) residential fittings where cost and weight matter more than thermal headroom.
How much cheaper is a PC housing than an aluminum one?
On the same size and shape, a PC housing typically lands 30–45% cheaper per unit, mainly on raw material and cycle time. Tooling reverses the picture: an injection mould usually costs more than a die-casting die for the same part, so PC only wins the total cost at higher volumes.
What is the typical failure mode of a PC downlight housing?
Heat-related aging: yellowing near the light engine, embrittlement of clips and trim edges in months 12–24, and warping at the ceiling seat. The LED suffers too — higher junction temperature accelerates lumen depreciation, so the fitting dims years early.
Can I mix aluminum and PC housings in one product range?
Yes — many brands run aluminum for the commercial core and PC for the low-wattage residential tail. Watch finish consistency: powder-coated aluminum and moulded PC render white slightly differently, so approve both against the same colour standard before committing.
Send us your wattage and target price
Tell us the light engine you plan to use and the warranty you intend to offer — we will come back with a material recommendation, the thermal reasoning behind it, and tooling options for both routes. That conversation costs you an email; the wrong material costs you a market.