E27 vs B22 vs E14 vs GU10: How to Choose the Correct Light Bulb Base

Buying a replacement light bulb should be straightforward. Yet many customers reach the checkout page knowing the wattage and colour they want—but not whether their fitting requires an E27, B22, E14 or GU10 base.

That small detail determines whether the globe will fit at all.

An E27 bulb cannot be installed in a B22 holder. An E14 bulb may look similar to an E27, but its screw base is considerably smaller. A GU10 spotlight may resemble an MR16 lamp from the front, while using a completely different connection and electrical supply arrangement.

The safest approach is simple:

Match the new bulb’s base code to the code on the existing bulb or lamp holder before comparing wattage, lumens or colour temperature.

Light-bulb base codes use letters to identify the connection system and numbers to indicate the approximate base diameter or distance between pins in millimetres. Screw, bayonet and pin-based globes are therefore not interchangeable merely because their glass shapes look similar.

Quick comparison: E27, B22, E14 and GU10

What does a light bulb base do?

The base—or cap—is the lower section of the globe that connects it to the light fitting.

It performs three essential functions:

1. It holds the bulb securely in position.
2. It makes the electrical connection.
3. It ensures that only a compatible bulb can be installed in the holder.

The base is separate from the bulb’s shape, brightness and lighting technology.

For example, an E27 base can be found on:

• Standard A60 LED globes
• Decorative filament bulbs
• Large G125 globes
• PAR reflector lamps
• Coloured lamps
• Smart bulbs
• Specialist infrared lamps

Similarly, two bulbs can both have an A60 shape while one uses an E27 screw base and the other uses a B22 bayonet base.

Never identify a globe by shape alone.

What is an E27 bulb?

E27 is a medium Edison screw base. The “E” refers to the Edison screw connection, while “27” indicates an approximate base diameter of 27mm. It is installed by placing the threaded base into the holder and turning it clockwise.

E27 is one of the most versatile bulb bases used in residential and commercial lighting. It is commonly found in standard lamps, pendants and general-purpose fittings.

How to identify E27

Look for:

• A metal screw thread
• A relatively wide base
• “E27” printed on the globe, packaging or fitting
• A holder with an internal threaded sleeve

Do not confuse E27 with E14. Both screw into their holders, but the E14 base is significantly narrower.

Where is E27 commonly used?

E27 is suitable for many conventional lighting applications, including:

• Pendant lights
• Table and floor lamps
• Open decorative fittings
• Wall lights
• Outdoor fittings
• Standard ceiling fixtures
• Large decorative filament globes

E27 is also commonly used where the bulb is intended to form part of the visual design. Decorative G45, ST64, G95 and G125 filament globes frequently use the E27 connection.

E27 product examples

For practical everyday lighting, the LED Basic A60 E27 7W Opal Bulb 6000K combines a standard A60 shape with an E27 screw base.

For exposed decorative fittings, the WHL&E B3-05 4W G45 Filament Bulb E27 3000K provides a compact globe shape and warm white light.

Whitehouse Lighting and Electrical’s catalogue also includes E27-compatible pendants, wall lights, outdoor fittings and specialist bulbs, showing how broadly this base is used across different lighting categories.

What is a B22 bulb?

B22 is a bayonet-style bulb base. Instead of a screw thread, it has two small pins projecting from opposite sides of the metal cap.

To install it:

1. Align the pins with the slots in the holder.
2. Push the bulb inward.
3. Turn it until it locks into place.

The “B” identifies the bayonet connection, while “22” refers to an approximate cap diameter of 22mm. B22 and E27 are both widely used for general household lighting, but their connection systems are completely different.

You may also encounter the designation B22d on technical product information. In normal retail use, this is commonly shortened to B22.

How to identify B22

Look for:

• Two pins on opposite sides of the cap
• A smooth metal body without a screw thread
• Two separate electrical contacts underneath
• “B22” or “B22d” printed on the bulb
• A holder with two L-shaped locking slots

Customers often describe B22 as:

• Clip-in
• Pin-type
• Push-and-turn
• Bayonet
• Twist-in

“Clip-in” is understandable in everyday conversation, but bayonet is the more accurate technical term.

Where is B22 commonly used?

B22 is frequently found in:

• Conventional household ceiling fittings
• Basic pendant holders
• Older and established residential installations
• General-purpose table lamps
• Utility areas
• Standard replacement-globe applications

B22 product examples

For everyday daylight-white lighting, consider the LED Basic A60 B22 7W Opal 6000K.

For warmer residential lighting, the Flash A60 9W Opal B22 3000K provides a warm white output with the same bayonet connection.

Whitehouse Lighting and Electrical also carries separate B22 lamp holders, including the WHL&E White B22 Globe Holder, for suitable installations and replacement work. Product fitting and electrical work should be performed appropriately and, where required, by a qualified electrician.

E27 vs B22: which one do you need?

Neither base is inherently better. The correct choice is determined by the holder already installed in the fitting.

Choose E27 when the holder has:

• An internal screw thread
• No bayonet slots
• An E27 marking

Choose B22 when the holder has:

• Two side slots
• A push-and-turn locking action
• A B22 marking

An adaptor may appear to offer a quick solution, but it adds length and can affect how the bulb sits inside the shade. It may also create clearance, heat-management or mechanical-support problems in fittings not designed for an adaptor.

Where possible, use the correct bulb base directly rather than adapting an incompatible globe.

What is an E14 bulb?

E14 is a small Edison screw base. It uses the same basic threaded connection as E27, but its approximate diameter is only 14mm.

It is commonly called:

• Small Edison screw
• SES
• Small screw bulb
• Chandelier bulb
• Candle bulb base

E14 is commonly associated with compact decorative fittings, chandeliers, sconces and smaller lamps.

How to identify E14

Look for:

• A narrow threaded metal base
• A base substantially smaller than E27
• “E14” or “SES” printed on the bulb or fitting
• A slim candle, golf-ball, pygmy or reflector bulb shape

Remember that the bulb’s shape does not conclusively determine its base. Candle bulbs, for example, are often E14, but E27 candle bulbs also exist.

Where is E14 commonly used?

E14 bulbs are frequently installed in:

• Chandeliers
• Decorative wall lights
• Bedside lamps
• Candle-style fittings
• Small pendant lights
• Pygmy or appliance fittings
• Display lighting
• Compact reflector fittings

The Whitehouse Lighting and Electrical range includes E14 candle, golf-ball, reflector, pygmy and specialist appliance bulbs.

E14 product examples

For chandeliers and decorative fittings, the Brightstar 4W LED Filament Candle Bulb E14 2700K creates a warm, traditional appearance using efficient LED filament technology.

For crisp everyday illumination, the Flash 5W LED Candle Bulb E14 6000K provides a daylight-white alternative.

For small fittings and indicator applications, the Flash 1W E14 LED Pygmy Bulb 6400K uses a compact E14 connection and pygmy shape.

Specialist appliance bulbs must be chosen according to their intended application. A normal decorative LED should not automatically be used as an oven-lamp replacement merely because both bulbs have an E14 base.

E14 vs E27: what is the difference?

The main difference is the diameter of the screw base:

• E14: approximately 14mm
• E27: approximately 27mm

E14 is commonly used in compact decorative fittings. E27 is generally used in larger, standard household fittings.

They are not interchangeable.

Trying to force an E27 globe into an E14 holder—or an E14 globe into an E27 holder—can damage the lamp holder and create an unsafe electrical connection.

What is a GU10 bulb?

GU10 is a two-pin twist-lock base commonly used on mains-voltage spotlights and downlights.

Unlike E27 and E14, it does not use a screw thread. Unlike B22, it does not have pins projecting from the sides.

A GU10 has two short pins underneath the bulb. Each pin has a widened end that locks into the holder when the globe is pushed in and rotated. The code’s number corresponds to the distance between the pins, and GU10 is classified as a twist-and-lock base.

How to identify GU10

Look for:

• Two short pins underneath the bulb
• Widened or mushroom-shaped pin ends
• A flat or spotlight-style front
• “GU10” printed on the lamp
• A holder that requires a push-and-twist movement

Where is GU10 commonly used?

GU10 bulbs are commonly installed in:

• Recessed ceiling downlights
• Surface-mounted spotlights
• Track lighting
• Adjustable wall lights
• Kitchen lighting
• Retail display lighting
• Accent lighting
• Outdoor up-and-down fittings designed for GU10 lamps

A representative GU10 LED product sold in South Africa operates at 220–240V and uses a focused beam, illustrating why GU10 is normally associated with directional mains-voltage lighting rather than general omnidirectional globes.

GU10 product examples

For warm accent lighting, the Flash 3W Clear LED Downlight Bulb 3000K provides a GU10-compatible connection and focused warm-white output.

For cool daylight illumination, the Flash 5W LED GU10 Frosted 6000K is suited to compatible downlights and spotlights.

For adjustable colour temperature, the O-Lite 5W LED GU10 Spotlight 3CCT allows the lighting colour to be selected according to the room and application.

Whitehouse Lighting and Electrical’s catalogue also includes GU10-compatible downlight fittings, kits, surface spotlights and outdoor fixtures.

GU10 vs MR16: do not rely on the bulb shape

GU10 and MR16 lamps are frequently confused because they can have a similar reflector shape and diameter.

However, MR16 describes a reflector format rather than one single electrical base. Many MR16 lamps use a GU5.3 two-pin base.

The distinction is important:

Official product specifications show 220–240V operation for a GU10 LED spotlight, while GU5.3 products are classified separately as low-voltage LED spots.

Never replace a GU5.3 lamp with a GU10—or vice versa—based only on the reflector shape. Confirm the base and operating voltage first.

The base does not determine brightness

The base tells you whether the bulb will connect to the fitting. It does not tell you how much light the bulb produces.

After confirming the correct base, compare the following:

Lumens

Lumens measure visible light output. A higher lumen value normally means a brighter bulb.

Do not assume that every 7W LED has the same brightness. LED efficiency varies between products, so two bulbs with the same wattage can produce different lumen outputs.

Wattage

Wattage measures electrical power consumption.

It also matters because fittings may specify a maximum permitted wattage. Never exceed the fitting manufacturer’s stated limit.

Colour temperature

Colour temperature is measured in Kelvin:

• 2700K–3000K: warm white
• Approximately 4000K: neutral white
• 6000K–6500K: daylight or cool white

Warm light is often used in bedrooms, lounges and dining areas. Neutral or daylight-white lighting is commonly chosen for kitchens, garages, offices and task areas.

Dimming compatibility

A bulb should only be used with a dimmer when it is specifically marked as dimmable.

The dimmer must also be compatible with LED lighting. A dimmable bulb connected to an incompatible dimmer may flicker, buzz or operate across only part of its intended dimming range.

Bulb dimensions

Matching the base does not guarantee that the bulb will physically fit inside the shade.

For example, an E27 A60 bulb and an E27 G125 bulb use the same screw connection, but the G125 globe is much larger.

Check:

• Overall bulb height
• Globe diameter
• Shade opening
• Distance from the holder
• Ventilation around the bulb
• Whether the fitting is enclosed

Beam angle

Beam angle is especially important for GU10 spotlights.

A narrow beam concentrates light on a smaller area and is useful for highlighting artwork, shelving or architectural features. A wider beam spreads light across a broader surface and may suit general downlighting.

How to identify your bulb base before ordering

Use this process:

1. Switch off the light

Turn the light off and allow the bulb to cool completely.

Where there is uncertainty about the fitting, wiring or isolation, consult a qualified electrician rather than working on an energised installation.

2. Remove the old globe carefully

• E27 and E14: turn anticlockwise.
• B22: press inward and turn anticlockwise.
• GU10: press lightly and rotate anticlockwise.

Do not force a bulb that does not move normally.

3. Read the printed code

Look around the metal or plastic base for:

• E27
• B22 or B22d
• E14 or SES
• GU10

The code may also appear on the original packaging or fitting label.

4. Inspect the connection

When the code has worn away, check the physical design:

• Wide screw thread: probably E27
• Narrow screw thread: probably E14
• Two side pins: B22
• Two short bottom pins with widened ends: GU10

5. Photograph the old bulb

Take a clear photograph showing:

• The base
• The entire bulb
• The printed specifications
• The lamp holder

This makes it easier for a retailer to help identify the correct replacement.

6. Match more than the base

Before ordering, also confirm:

• Voltage
• Wattage
• Lumens
• Colour temperature
• Dimming capability
• Shape
• Physical size
• Indoor or outdoor suitability

Can you change a fitting from B22 to E27?

The lamp holder itself can sometimes be replaced, but this is not the same as changing a bulb.

Replacing a fixed lamp holder involves electrical connections and must be done correctly. Do not modify the fitting merely because a preferred bulb is available in a different base.

South African general-service lamps are subject to compulsory safety requirements, including requirements covering self-ballasted LED lamps, product approval and conformity before regulated products are offered for sale. Fixed electrical installation work should be handled in accordance with applicable requirements and by a competent person.

In most cases, buying the correct bulb for the existing holder is simpler and safer than converting the fitting.

Common bulb-base buying mistakes

Mistake 1: Ordering by bulb shape

“A60”, “candle”, “golf ball” and “reflector” describe shape—not necessarily the connection.

Always check the base separately.

Mistake 2: Calling every screw bulb E27

E14 is also a screw-in bulb. The difference in diameter matters.

Mistake 3: Assuming B22 and E27 are interchangeable

Both may be used on standard household globes, but their holders are mechanically different.

Mistake 4: Confusing GU10 with GU5.3

Similar reflector shapes do not mean compatible bases or voltages.

Mistake 5: Choosing watts before checking lumens

Watts indicate power consumption. Lumens indicate brightness.

Mistake 6: Ignoring the fitting’s maximum wattage

The bulb must remain within the fitting’s specified electrical and thermal limits.

Mistake 7: Using a normal bulb in a specialist appliance

Ovens, refrigerators, heat lamps and other appliances may require bulbs designed for specific temperatures or operating conditions.

Frequently asked questions

Is E27 screw-in or clip-in?

E27 is a screw-in connection. Turn the bulb clockwise to install it in a compatible holder.

Is B22 screw-in?

No. B22 is a bayonet connection. Push the bulb into the holder and turn it to lock.

What is the difference between E14 and E27?

Both are Edison screw bases. E14 has an approximate diameter of 14mm, while E27 is approximately 27mm.

Can I use an E14 bulb in an E27 holder?

Not directly. They are different sizes and require different lamp holders.

What does GU10 mean?

GU10 identifies a two-pin twist-lock base. The pins are pushed into the holder and rotated to secure the lamp.

Is GU10 the same as MR16?

Not necessarily. MR16 usually refers to the reflector format. Many MR16 lamps use a GU5.3 base, while GU10 lamps use a twist-lock base and are commonly designed for mains-voltage operation.

Which bulb base is most common in South Africa?

E27 and B22 are both widely encountered in general household lighting. The correct choice depends on the lamp holder already installed.

Can the base tell me whether the bulb is warm white?

No. The base only identifies the connection. Check the Kelvin rating to determine colour temperature.

Can all E27 or GU10 bulbs be dimmed?

No. Only bulbs specifically marked as dimmable should be used with a compatible dimmer.

Final buying checklist

Before adding a globe to your basket, confirm:

• Correct base: E27, B22, E14 or GU10
• Correct operating voltage
• Suitable lumen output
• Preferred colour temperature
• Dimmable or non-dimmable
• Correct bulb shape
• Suitable physical dimensions
• Appropriate beam angle
• Indoor or outdoor suitability
• Compatibility with enclosed fittings
• Maximum wattage permitted by the fitting
• Specialist requirements for appliances or heat lamps

Find the correct globe the first time

The bulb base should always be the first specification you check.

Choose:

• E27 for a standard screw-in holder.
• B22 for a bayonet push-and-turn holder.
• E14 for a smaller screw-in holder commonly used in decorative fittings.
• GU10 for a compatible twist-lock spotlight or downlight holder.

Once the base is confirmed, compare lumens, wattage, colour temperature, beam angle, dimensions and dimming compatibility.

Explore Whitehouse Lighting and Electrical’s range of LED globes, filament bulbs, downlights and lamp holders, or send the team a clear photograph of your existing bulb and fitting for assistance.

For help choosing between standard and decorative LED options, read our related guide: LED vs Filament Bulbs: Which Globe Is Best for Your Home?