G9, G4, R7S, and E14 Lamp Caps — LED Replacements and Halogen Equivalents for UK Electricians

When a customer calls you to replace a blown lamp and hands you an unfamiliar bi-pin capsule or a two-pronged loop fitting, knowing your lamp cap types saves time and prevents a wasted return visit. While GU10 downlights dominate new domestic installations, older fittings — bathroom mirrors, kitchen extractors, integrated cooker hoods, garden floodlights, and decorative pendants — rely on G9, G4, R7S, and E14 cap types that are still widely in use across UK housing stock.

This guide explains each cap type, where you will find them on site, what halogen wattages they typically replace, and how to choose the right LED equivalent for a direct swap.

G9 Loop-Pin Lamps

The G9 is a 240 V mains-voltage lamp with two small ceramic loop pins set 9 mm apart. It requires no separate transformer and fits directly into the mains supply, which made it the cap of choice for bathroom shaver lights, integrated kitchen uplighters, bedside lamp shades, and decorative wall sconces from the 1990s through to the early 2010s.

Typical halogen G9 wattages are 25 W, 33 W, and 40 W. LED equivalents deliver the same light output from 3–5 W — a reduction of roughly 80–85 % in power draw for the same fitting.

When replacing G9 lamps, confirm the fitting's maximum wattage printed inside the lampholder. Most ceramic G9 holders are rated for 40 W halogen, but older plastic holders may be rated lower. LED G9 lamps run far cooler than halogen, so any holder rated for the original halogen wattage is safe to use with the LED replacement.

The Meridian G9 240V Energy Saving Lamp is a direct mains-voltage retrofit for existing G9 fittings. It is one of the most cost-effective halogen-to-LED conversions available — the energy saving pays back within the first month of use in a frequently-lit room.

Meridian G9 240V Energy Saving Lamp

G4 Bi-Pin Capsule Lamps

The G4 is a low-voltage lamp with two straight metal pins set 4 mm apart, typically operating at 12 V DC or AC. You will find G4 lamps in under-cabinet lighting in kitchens, recessed capsule fittings in caravans and motorhomes, marine interior lighting, display cabinet puck lights, and some decorative pendant fittings with low-voltage drivers.

Halogen G4 lamps commonly come in 10 W, 20 W, and 35 W versions. The 12 V supply means a separate transformer or driver is always required — check whether the existing transformer is dimmable if the customer requires dimming, and whether it is rated for LED minimum loads (many older halogen transformers have a minimum load of 20–40 W and will flicker or buzz with a 1–2 W LED load).

When selecting an LED G4 replacement, look for a lamp rated for both 12 V AC and 12 V DC if the transformer type is unknown, as some drivers output DC while others output AC. A lamp that accepts both avoids compatibility issues.

The Integral LED G4 200LM 1.6W 2700K Non-Dimmable provides a warm white 2700 K output at 200 lumens from just 1.6 W — equivalent to a 10 W halogen capsule. The 320-degree beam angle gives an omnidirectional spread that suits open-reflector fittings well.

Integral LED G4 200LM 1.6W 2700K Non-Dimmable

R7S Linear Lamps (J-Lamps)

The R7S is a mains-voltage linear lamp — sometimes called a J-lamp or double-ended lamp — with recessed contacts at each end, set 78 mm or 118 mm apart in the most common sizes. The R7S cap type is used in exterior floodlights, security lighting, indoor halogen floodlight fittings, work lights, and some designer floor lamps and uplighters.

Halogen R7S lamps are high-wattage fittings — commonly 100 W, 150 W, 200 W, and 300 W — making them among the highest-priority halogen types to replace on energy grounds. A direct LED R7S replacement in a 150 W floodlight fitting that runs 6 hours a day will save approximately 860 kWh per year and, at current UK electricity rates, around £250 per year for a single fitting.

When replacing R7S lamps, confirm the physical length (78 mm or 118 mm) before ordering, as the two sizes are not interchangeable. Also verify the fitting's heat dissipation: LED R7S lamps run much cooler, but some older enclosed floodlight housings were designed around halogen heat to keep the lens clear in wet weather — inspect the seal and lens after replacement.

The Integral LED R7S 620LM 5.2W 4000K Non-Dimmable is a 78 mm linear LED delivering 620 lumens at a cool white 4000 K colour temperature. At 5.2 W it replaces a 50–60 W halogen R7S. For higher-output applications, the 9.5 W 1250LM version provides a closer match to 100 W halogen output.

Integral LED R7S 620LM 5.2W 4000K Non-Dimmable

E14 Small Edison Screw (SES) Lamps

The E14 — also known as SES or small Edison screw — is a 14 mm diameter screw cap widely used in decorative pendant fittings, chandelier arms, bedside table lamps, vintage-style filament designs, bathroom vanity strips, and small wall lights. It is the smaller sibling of the E27 GLS cap and uses the same screw mechanism at a reduced diameter.

Halogen E14 candle lamps typically run at 28 W or 42 W and produce a warm directional glow suited to decorative use. Customers replacing these are often prioritising aesthetics as much as energy efficiency, so a filament-style LED that retains the visible filament glow is often the preferred choice over a conventional frosted LED bulb.

The Meridian 4W Filament E14 Tip Candle Lamp 3000K is a decorative tip-candle shape producing warm 3000 K light with a visible filament coil. At 4 W, it replaces a 25–28 W halogen E14 candle and is well suited to chandeliers, wall lights, and pendant clusters where visual appearance matters. The tip candle form factor — pointed at the top — is the style most commonly found in ornate fittings.

Meridian 4W Filament E14 Tip Candle Lamp 3000K

How to Identify the Cap Type on Site

If the old lamp is still in the fitting, the cap type is usually printed or stamped on the lamp base or the glass envelope. Key identifiers:

• G9: Two small ceramic loops, roughly oval cross-section, visible side by side — found in mains-voltage fittings, no separate transformer
• G4: Two straight, thin metal pins, 4 mm apart, often in a star-shaped or flat reflector capsule — always 12 V, always has a transformer nearby
• R7S: Linear tube 78 mm or 118 mm long with recessed contacts at each end — always mains voltage, usually in a floodlight or uplighter housing
• E14: Threaded screw base 14 mm in diameter — usually in a decorative pendant, wall light, or chandelier arm

If the lamp is already removed and unmarked, measure the pin spacing for G-type caps or the base diameter for E-type caps. A simple ruler or digital caliper resolves any ambiguity.

LED vs Halogen: Key Considerations

Replacing halogen lamps with LEDs is the right call on energy grounds in nearly every case, but a few practical checks ensure a clean installation:

• Dimmer compatibility: LED minimum loads are much lower than halogen. Most trailing-edge and leading-edge dimmers designed for halogen will need to be replaced with an LED-compatible dimmer if the customer wants to retain dimming. Check the dimmer's minimum load rating against the total LED wattage on the circuit.
• Transformer compatibility (G4 and other 12 V types): Old magnetic transformers are incompatible with many LED drivers. Electronic transformers work with most LED lamps, but check the manufacturer's minimum load. If in doubt, replace the transformer at the same time as the lamps.
• Colour temperature: Halogen lamps produce 2700–3000 K warm white light. Most domestic customers prefer a like-for-like warm white replacement. Cool white (4000 K+) is better suited to task lighting, kitchens, and commercial applications.
• Beam angle: G9 and E14 filament LEDs typically produce omnidirectional light. G4 capsule LEDs are more directional. R7S LEDs vary — check the beam angle against the fitting's intended illumination area.

Summary

G9, G4, R7S, and E14 cap types are common on UK retrofit and refurbishment work. Stocking the most popular LED equivalents — G9 for bathroom and kitchen fittings, G4 for 12 V display and under-cabinet lighting, R7S for floodlights and uplighters, and E14 for decorative pendants and chandeliers — means you can complete a lamp replacement in a single visit rather than waiting for a specialist order.

All four lamp types are available at APM Electricals for next-day dispatch.

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APM Electricals
39 Villiers Road, Southall, Middlesex, UB1 3BN
Tel: 0208 575 8880