An AR111 LED bulb is a large 111 mm reflector lamp that slots into the same fittings as the old 12 V halogen AR111 and throws a strong, tightly controlled beam. With a G53 cap it always runs from a transformer or LED driver, so a good swap depends on the beam angle, the length of the lamp and what is powering it, not just the wattage on the box.
You'll mostly find AR111s in gimbal downlights with square or round bezels, in surface-mounted box spots and on track. Shops, galleries, bars and hotel lobbies have used them for decades because one lamp can light a whole display. At home they tend to sit over a dining table or kitchen island, or pick out a painting from a high ceiling.
The name is a description: an aluminium reflector roughly 111 mm across. That is more than twice the width of an MR16, so there is room for a bigger reflector or lens and far more light pushed in one direction. Halogen versions came in 35, 50, 75 and 100 W and produced a lot of heat in the beam; LED versions use a fraction of the power, keep infrared off whatever they light and are typically rated for tens of thousands of hours instead of a few thousand.
The same 111 mm body is also made for mains voltage with a GU10 cap, often sold as ES111. Seen from below the two look alike, but they are not interchangeable. A G53 lampholder means a 12 V circuit with a transformer somewhere in the ceiling void. For the cap itself, AC and DC versions and how it differs from GX53, see G53 bulbs.
With a reflector lamp the beam angle shapes the result more than the wattage. Squeeze the same lumens into 8° instead of 24° and the centre of the pool becomes several times brighter, which is why spot specs quote candela (cd) as well as lumens. As a guide, a 450 lm, 24° LED reaches about 1800 cd: roughly 200 lux at the centre of the pool from 3 m away.
| Job | Beam angle | Pool from 3 m | Colour temperature | CRI |
|---|---|---|---|---|
| Sculpture, single object, very high ceiling | 8° | about 0.4 m | 3000 K | 90+ |
| Painting or artwork | 12–15° | about 0.6–0.8 m | 2700–3000 K | 95+ |
| Dining table, kitchen island | 24° | about 1.3 m | 2700–3000 K | 90+ |
| Shop display, clothing rail | 24–36° | about 1.3–1.9 m | 3000–4000 K | 90+ |
| General wash, counters, hallways | 40–45° | about 2.2–2.5 m | 3000–4000 K | 80+ |
In a typical UK room with a 2.4 m ceiling an 8° beam lands as a small, hard-edged circle, which looks great on an object and harsh over a table. If you are unsure, 24° is the safe middle ground.
As a rough guide, a 7–8 W LED giving 400–500 lm replaces a 50 W halogen, 11–12 W and around 800 lm covers 75 W, and 13–15 W stands in for 100 W. Compare lumens and candela rather than watts, because two lamps of the same wattage can differ a lot in how much light lands on the target. For food, fabrics and art, go for CRI 90 or higher; halogen scored a perfect 100 and a low-CRI LED will make colours look flat next to it.
Most trouble after a swap comes from the transformer, not the lamp. Electronic halogen transformers need a minimum load, often a few tens of watts, and a single LED drawing 7 W may fall short. The result is flicker, a faint buzz or a lamp that won't start. The cure is a 12 V constant-voltage LED driver sized to the total load with about 20% headroom, or a lamp the manufacturer lists as compatible with your transformer. Some AR111 LEDs accept 12 V AC or DC; others are DC only and won't run from an AC transformer.
Dimming needs a matched set: a dimmable lamp, a compatible transformer or driver and the right dimmer, which for electronic transformers is usually trailing-edge. Changing a transformer or dimmer means working on fixed wiring, so leave it to a qualified electrician.
Diameter is fixed, length isn't. An LED with a finned heat sink can be deeper and heavier than the halogen it replaces, so measure the depth of the fitting and check the spring clips still hold the lamp firmly. Electronics dislike being boxed in, so leave some air around the body in sealed or insulated ceilings. The lamps themselves are usually rated IP20, so outdoors they belong only inside a fitting built for it. Dust them dry, with the power off and the lamp cool.
A reflector lamp with an aluminium reflector about 111 mm in diameter. It comes with a G53 cap for 12 V systems or a GU10 cap for mains voltage, as halogen or LED.
In a G53 fitting it usually works if the LED is 12 V and compatible with the transformer. If the transformer is underloaded or not LED-friendly, expect flicker, buzzing or early failure.
Look at the cap of the lamp you are replacing. Two flat blade contacts, with a transformer in the circuit, mean G53 at 12 V. Two stubby pins with wider tips that twist and lock mean GU10 at mains voltage. Converting one to the other is a wiring job, not a bulb swap.
Halogen versions were usually 35–100 W. LED replacements typically draw 5–15 W, with 7–8 W standing in for 50 W.
Many are, but only when lamp, transformer or driver and dimmer are compatible. Check the manufacturer's compatibility list before buying a full set.
Usually a recessed gimbal downlight, single or in twin and triple frames, or a surface box spot or track head, made to hold the 111 mm lamp and let you aim it.
Weighing up an AR111 against a smaller spot or a screw-in bulb? More on other caps and shapes in light bulbs.
