Tutorial
Replace halogen GU10 and MR16 spots with LED
To claim it replaces a 50 W MR16 halogen, an LED must give at least 540 lm in a 90° cone; for a 50 W mains GU10 (PAR16), 300 lm (EU Regulation 1194/2012). Compare lumens, not watts.
1. Identify the spot
- GU10: two short pins with feet, push and twist. Mains voltage: 230 V in the UK, 120 V in the US. No transformer.
- MR16 (GU5.3): two thin straight pins, push in. 12 V, fed by a transformer in the ceiling void.
2. Match the light
| Halogen replaced | UK/EU minimum Φ90° | Example |
|---|---|---|
| 35 W GU10 (mains PAR16) | 200 lm | – |
| 50 W GU10 (mains PAR16) | 300 lm | Philips CorePro 4 W, 350 lm (UK); Philips 6 W, 400 lm (US) |
| 35 W MR16 (GU5.3) | 300 lm | Philips 4 W, 380 lm (US) |
| 50 W MR16 (GU5.3) | 540 lm | check Φ90° on the datasheet |
Source: Regulation (EU) 1194/2012, Annex III, table 6 (now table 4 of Delegated Regulation (EU) 2019/2015; retained in GB). For LEDs the value is also multiplied by the lumen maintenance factor, and by 0.8–0.9 for beams under 20°. US packaging is not bound by these EU values. LED figures come from the listings below. Keep the beam angle (usually 36°–40°). Choose 2700–3000K to match halogen's warm light.
3. MR16: the transformer trap
Old electronic transformers often need a minimum load of 20–35 W. A single 4 W LED is below it: flicker or nothing. Fixes: an LED driver rated for the total LED wattage, or replace the MR16 fittings with GU10 mains fittings (in the UK, that is electrical work under BS 7671; in a bathroom zone it is notifiable under Part P in England and Wales).
4. Dimmers
See our dimmable LED guide: use dimmable LEDs and an LED-rated (trailing-edge or CL) dimmer.
5. Safety and fire
Turn off the circuit at the consumer unit (UK) or breaker (US) and let halogens cool: they run at well over 100 °C. In the UK, many ceiling spots are fire-rated downlights that maintain the ceiling's fire resistance: keep them. In the US, recessed cans in contact with insulation must be IC-rated.
Bulbs
UK · GU10 230 V
Philips CorePro LED GU10 4W, 4000K, dimmable (10-pack)
Listing: 50 W halogen replacement, 350 lm, 36° beam, CRI 80, dimmable with compatible dimmers, energy class F.
Check price on Amazon UKUK · GU10 230 V
Philips LED Classic GU10 4.6W, 4000K (6-pack)
Listing: 50 W equivalent, 390 lm, CRI 80, 220–240 V, non-dimmable, energy class F.
Check price on Amazon UKUS · GU10 120 V
Philips 465054 LED GU10 6W, 3000K, dimmable (3-pack)
Listing: 400 lm, 35° flood, 50 W equivalent, dimmable. A 120 V GU10: do not use it on 230 V UK circuits (and vice versa).
Check price on Amazon USUS · MR16 12 V
Philips LED MR16 4W, 3000K, dimmable (3-pack)
Listing: 380 lm (4 W = 50 W), clear, flicker-free, low-voltage GU5.3 pins.
Check price on Amazon USProduct data below is taken from the manufacturer's listing on Amazon, checked on 22 October 2026. Prices change: check the current price before buying. As an Amazon Associate I earn from qualifying purchases.