E26 or E27? The difference between e26 & e27 bulbs and how to choose them

You may be wondering if E26 and E27 are the same, whether they are compatible, and can you use an E26 bulb in an E27 socket or vice versa? But before you do, be aware of the safety risks!

Beware of incorrect advice!

Many manufacturers and light bulb retailers will simply tell you that E26 and E27 bulb bases and sockets are compatible. That said, you can safely fit an E26 bulb into an E27 socket, and vice versa.

And they'll all say, "Well, the E27 is 27mm, and the E26 is 26mm, and they fit perfectly. They're almost the same!"

This is incorrect advice based on misinformation!

When manufactured according to widely accepted IEC standards, E26 and E27 lamp bases actually have the same diameter specifications from 26.05mm (minimum) to 26.45mm (maximum).

The difference between E26 and E27 is the minimum distance between the bottom contact (live contact) and the thread. The reason for this difference is that the E26 and E27 standards are designed for 120V AC and 240V AC, respectively, and have different line voltage levels.

In fact, in most cases it turns out that the bases and sockets of E26 and E27 lamps are physically interchangeable. This means you can physically install an E26 bulb into an E27 socket and vice versa.

However, just because a bulb is securely inserted and working does not mean that the lamp installation meets the electrical safety standards for which the lamp and lampholder were designed. Improper installation can increase the risk of short circuits and electrical fires.

In general, bulbs marked E27 are safe for use in E26 lampholders, but installing E26 bulbs in E27 sockets and using them at 240V AC may pose an electrical safety hazard.

We will then take a closer look at the differences between E26 and E27.

Physical differences between E26 and E27

Although it is generally said that there is a 1mm difference between E26 and E27 thread dimensions, the thread dimension requirements are virtually the same.

Below is a diagram and specifications comparing E26 and E27.

Electrical safety differences between E26 and E27

The mechanical differences mentioned above may seem trivial, but they exist because each lamp base corresponds to the voltage level used.

E26 lamps are primarily designed for the North American market, which uses 120V AC, while E27 lamps are designed for other markets, where 240V AC is the norm.

E27 bulbs are designed for use in higher voltage circuits, so additional precautions must be taken to ensure adequate spacing between the live and neutral contacts.

A specific explanation of why the above mechanical differences exist is as follows.

1) E27 uses longer screws because longer screws allow for more accurate alignment of the screw in the socket. If the screws are improperly aligned, the "live" contacts can be close to the neutral threads, increasing the risk of arcing or shorting.

2) E27 uses a wider thread root diameter to provide a safer, gap-free contact. This prevents moisture and debris from entering the socket. Higher voltage levels increase the risk of short circuits and electrical fires due to moisture and dirt.

3) E27 requires a higher insulator height to increase the distance between the live contacts and the neutral screw cap. This difference is relatively large and is necessary to avoid the risk of shorting.

Summary

• E26: Common in North America and works with 120V fixtures.
• E27: The standard for Europe, where voltage requirements are 220-240V.

1. When purchasing LED bulbs, do not assume that E26 and E27 are completely compatible. If possible, use E26 bulbs in 120V AC E26 sockets and E27 bulbs in 240V AC E27 sockets.
2. Although you may be able to safely use an E27 bulb in an E26 socket, you should not use an E26 bulb in an E27 socket.
3. Even though they are mechanically similar and can be interchanged, from an electrical safety perspective, using an E26 in a 240V AC E27 socket will result in poor insulation and reduced protection against short circuits and electrical fires.