Capsule lamps are small lamps with small two pin bases.  They are used in places such as desk lamps, display and decorative lighting.  The number next to each of the given titles for the lamps (G4, G6.35, G9 etc.) refers to the amount of millimetres between the two pins.  They are a great choice for a means of providing a bright light in a compact/small area.  They can vary in length, voltage and wattage so it is worth paying attention to this when purchasing one of these lamps.

G4 Capsule Lamps

• Pin Spacing: 4mm
• Voltage: 12V (Low Voltage)
• Technology: Halogen and LED
• Application: These are often used in smaller discreet fixtures such as accent lighting, cooker hoods, small spotlights, and decorative fittings.
• Transformer/Driver required?: As G4 lamps are often 12v they will usually require a transformer to convert 220-240v standard UK household voltage down to 12V.

G6.35 Capsule Lamps

• Pin Spacing: 6.35mm
• Voltage: 12V or 24V (Low Voltage)
• Technology: Halogen and LED
• Application: These can mostly be found in track lighting, display lighting, and floodlights.
• Transformer/Driver required?: As the G6.35 generally comes in 12v or 24v they will also require a transformer when running on mains voltage.

G9 Capsule Lamps

• Pin Spacing: 9mm
• Voltage: 220V–240V (Mains Voltage)
• Technology: Halogen and LED
• Application: These are the most common type of capsule lamp and they can be used in a wide range of domestic fittings, wall lights, and pendant lights. 
• Transformer/Driver required?: As these lamps most commonly run on 220-240v they should not require a transformer for most the majority of light fittings within the UK

Are these capsule bulbs being phased out?

No, capsule bulbs are not being phased out but you may find that the halogen bulbs you are used to are being phased out as the technology used to make these lamps is being converted to LED.  This is because of updated regulations within the UK and other countries focusing on improving energy efficiency within the lighting industry.  This has been an ongoing process for the UK since around September 2021.  You will still be able to find the bulbs you need with the G9, G4, G6.35 capsule base as it remains a popular choice for domestic and commercial decorative lighting.  

Can I replace a halogen capsule bulb with a LED version?

Yes you can and it is highly recommended to do so.  This drive for this conversion is motivated by the significant energy savings and extended lifespan offered by LEDs as they produce much more light whilst using a lower amount of wattage. However, there are three critical considerations when making this switch:

1. Transformer Compatibility: If your original 12V system runs on a transformer, you will need to make sure that the transformer is compatible with your newer LED capsule lamp, paying attention to the wattage of the bulbs you have and confirming that it is the same voltage. LED bulbs generally use less power and if the total wattage of the new LED bulbs is below the transformer's minimum load requirement it will not work as it should.  This can lead to the bulbs flickering or not lighting up at all.  You may need to swap your older transformer out for a compatible LED driver.
2. Do you need to dim the capsule lamp?: If you need to dim your capsule lamp you will need to make sure the transformer or driver you are looking to use is compatible with the bulb and the connecting dimmer switch.  If it is not this could again lead to the bulbs flickering or not working with your dimmer at all.
3. Physical Size: Some LED replacements require a heatsink to function and because of this they might be slightly larger than the old halogen bulb. It is crucial to measure the space inside your light fixture to ensure the new LED capsule will fit within it.