H1 vs H4 Bulb: What’r the Differences?

Headlight bulbs are available in a variety of light sources, and each source has a different model. H1 and H4 halogen bulbs are typical halogen lamps that differ primarily in manufacturing, application, and pricing.

This post will compare H1 and H4 based on their filaments, nominal power, output, uses, and prices. They may look the same, but if you go deeper into their features, you will find that they are not interchangeable and should not be used as a replacement for the others.

Comparing Differences of H1 vs H4 Bulb


The number of filaments in each bulb is the fundamental distinction between the H1 bulbs and H4 bulbs. The H1 bulb is a halogen lamp with a single filament and power consumption of 55 watts at 12 volts. The H4 halogen bulb is a dual-filament halogen lamp that utilizes 60 or 55 watts at 12 volts depending on which filament is used.

Nominal power

These fittings all generate the same amount of light. However, the number of volts required and watts produced (also known as nominal power) vary for each bulb. To make matters even more confusing, most of these bulbs are available in various nominal power ratings.

Because each bulb demands and outputs a little different amount of electricity, replacing one bulb fitting out for another, such as an H1 for an H7, is unsafe. Consider the consequences of connecting an American appliance to a European power outlet: the appliance may overheat or get damaged. The same thing might happen to automobile bulbs. Fortunately, each bulb fitting has a distinct base that makes them tough to mix up.

It’s worth mentioning that the majority of issues will arise when transitioning between fittings. Unless you’re adding an aftermarket kit, you shouldn’t have any problems changing the voltage or wattage of your bulbs. Upgrade bulbs purchased from a reliable retailer that are completely safe to install and use.


The base, often known as the cap, is the bottom portion of the bulb that attaches to the socket. These various bases contribute to the inability to switch between fits. Most of the time, you don’t have to worry about your bulb’s base other than making sure it fits your car.

In accordance with the IEC 60061, the H1 lamp utilizes a P14.5s. It is a round metal prefocus base 14.5mm in diameter with two dimples and a flat so the H1 can be installed in a lamp with the right orientation.

The H4 is distinguished by its three-pronged base, which is unusual among these bulbs. H1 has two prongs on its bottom. This could be a significant factor when buying the bulbs you need for your vehicle.

Power and output

The H1 light has a nominal rating of 55 watts at 12 volts under ECE Regulation 37, which controls vehicle filament lamps in most countries, and a test rating of 68W (maximum) and 1550 lumens 15% at 13.2V. R37 also includes specifications for 6-volt, 55-watt, and 24-volt, 70-watt H1 lamps. The US government does not recognize ECE norms and instead follows its own.

The H1 is rated at 65W (maximum) and 1410 lumens 15% at 12.8V under these conditions. Despite the two sets of prescribed voltages and test methodologies, the bulbs themselves are the same; with some exceptions, 12-volt H1 lamps are routinely manufactured and tested to conform with both specifications.

On the other hand, the standard H4 headlight bulb only uses 60 watts on HIGH and 55 watts on LOW. The H4 HALOGEN bulb features a HIGH beam of 100 watts and a LOW beam of 90 watts.

This low beam outperforms the stock high beam. It’s a direct replacement for the factory bulb. Using higher power bulbs poses a risk of scorching the wire harness and headlight bucket, causing reflector distortion and burning out contact points in the relay. Be cautious if you use higher wattage lights, and examine your wiring and reflector for these symptoms.


With a single reflector, H4 bulbs may act as both low-beam and high-beam headlights. They are the most frequent type of motorbike bulb. H1 bulbs, on the other hand, necessitate the use of two bulbs per headlamp, each with its reflector.

When it comes to the bulbs in their headlamps, drivers don’t have many options. Because different bulb types have specific fittings, they cannot be interchanged. You can not just switch to another bulb fitting if your car requires H4 bulbs. The lone exception is the 9003 or HB2 bulb, which is interchangeable with H4 bulbs.

The H4, 9003, and HB2 bulbs are all essentially the same and can be used interchangeably. Many bulbs that meet this requirement will have all three labels on the box.

Other Facts About H1

ECE regulations require H1 lamps to emit white or selective yellow light. H1 lights must emit white light in order to comply with US requirements. Both ECE and the US specifications allow for a wide white light spectrums. Some H1 lamps have a slight blue or yellow tinge to the glass, but they nevertheless produce light that meets the white light criterion. H1 lamps can be optimized for longer life or luminance and higher flux. A filament with a longer life is wound on a bigger mandrel with a wider pitch – it’s the distance between the adjacent filament coils.

Other Facts About H4

H4 headlights are available in two types – halogen and LED, so which is better. Halogen bulbs are brighter and have a longer lifespan than standard incandescent bulbs. The LED does not burn out, unlike incandescent bulbs, but it does dim after some time.

LEDs offer more design freedom in headlights and other vehicle lights because they are smaller than bulb-type lighting.


H1 and H4 bulbs are almost the same price, ranging from $3 to more than $50. To execute the same work as a single H4, however, two H1s are needed.

Frequently Asked Questions

Are H4 and HS1 the same?

In fitting, the HS1 bulb is nearly identical to the considerably more common type H4 bulb. The electrical connector is the same. The only distinction is the plate. The HS1 and H4 have three indexed tabs on the base, so the bulb can only fit in one direction.

Can I fit the H4 bulb in the HS1 socket?

Yes, it will fit. However, they have different wattage. The CBF HS1s use 35/35w, while the H4s uses 60/55w.

Are H1 and H11 bulbs interchangeable?

H1 and H11 both belong to Group 1, which means they can be used for anything, including headlights, tail lights, and others. These bulbs are primarily utilized as headlights. Despite being in the same category, these bulbs are not interchangeable.

Are H1 and H3 bulbs interchangeable?

The H1 appears to be longer and slimmer, and the bases of the bulbs are different. A P14.5 bulb is used in the H1 bulb. The H3 bulb has a PK22s base with a wire projecting from the bottom. You cannot simply swap an H1 bulb for an H3 fitting, nor can you connect an H1 bulb to an H3 fitting.

Final Thoughts

Generally, H1 and H4 are different despite being in the same category as United Nations international standards. However, they are not interchangeable. H1 is used internally, usually in a four headlight set up, while H4 is outside.

Another noticeable difference is in its filament. The H1 light has a single bulb with a power consumption of 55 watts at 12 volts. On the other hand, the H4 has two bulbs with a high and low beam of 90 watts. You need two H1 to achieve the brightness H4 can provide. You might have difficulty deciding which is the correct bulb for your vehicle if you do not have the right information. We hope this post provides the data you need. If you have questions or want to share your thoughts, feel free to comment below.

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