What is the difference between HS1 bulbs and H4 bulbs?
4 Answers
HS1 bulbs and H4 bulbs differ in the following aspects: HS1 bulbs have a power rating of 35W/35W, while H4 bulbs have a power rating of 55W/60W. Additionally, HS1 bulbs are standard for motorcycles according to national regulations, whereas H4 bulbs are designed for automotive use. Below are the detailed specifications: 1. H4 bulbs: H4 bulbs are a type of bulb specification and model used for car headlights (also known as headlamps). H4 bulbs are dual-filament, three-pin bulbs that combine both low beam and high beam functions in a single bulb. The standard power ratings are 55W for low beam and 60W for high beam; alternatively, some models may have 90W for low beam and 100W for high beam. 2. HS1 bulbs: According to national standards, the headlights of domestically produced motorcycles must not exceed 35/35W. Therefore, HS1 bulbs are specifically designed for motorcycles (as a standard configuration), and any deviation from this would result in failing factory inspection.
Previously, when my car's lights were dim, I learned the difference between HS1 and H4 headlights while replacing the bulbs. The HS1 bulb is a single-filament type, mainly used for high beams or single-light positions, such as fog lights. It's simple to install, with a round PK22s base. The H4, however, is different—it's a dual-filament bulb integrating both high and low beams, with one filament for high beam and another for low beam, allowing automatic switching. Its base is P43t with three prongs. This difference affects practical use: when driving at night, H4 bulbs are safer because you don’t need to manually switch beams; adjusting directly on the headlight can prevent dazzling oncoming traffic. In contrast, the HS1 is fixed in one mode, requiring additional lights to compensate. Cost-wise, H4 bulbs are slightly more expensive and a bit more complex to install, as the filament positions need alignment. However, many cars now come standard with H4 headlights, so always check the vehicle manual before replacing bulbs to avoid affecting visibility. I later found this knowledge quite practical, especially on rural mountain roads—good headlights can prevent many accidents.
As someone who enjoys studying automotive electronics, I've found the core difference between HS1 and H4 bulbs lies in their electrical design. The HS1 is a single-filament bulb with approximately 55W power output. Its simple structure provides stable illumination but only suits single-beam mode, such as dedicated high beam usage. The H4 features a dual-filament design - its low beam filament has a shield blocking partial light while the high beam operates at full brightness. With 55/60W power rating, it can automatically switch beams to provide dynamic lighting effects. This difference stems from filament arrangement and base design: HS1 uses single-point connection whereas H4 adopts three-point interface for better control. In practice, H4 offers superior brightness and wider coverage, particularly useful for urban night driving by eliminating manual operation and reducing distraction. However, single-filament bulbs like HS1 work better as auxiliary lights and may have slightly longer lifespan due to simpler construction. While modern vehicles increasingly adopt LED alternatives, OEM halogen bulbs remain mainstream. Through my own testing, I've learned that bulb selection must consider vehicle configuration - forced model changes should be avoided as they may compromise circuit safety.
When I first bought my car, I was torn between the choices of bulb types, as HS1 and H4 are quite different. The H4 bulb combines high and low beams into one, allowing easy switching between them with a single bulb. On the other hand, the HS1 is single-function only—for example, if installed in the high beam position, it will only emit high beam light. The installation differences are notable: the H4 bulb has a larger head with two filaments stacked together, while the HS1 is simpler and more compact in structure. Their brightness is similar, but the H4 is more widely used and suitable for main headlights, enhancing nighttime driving safety. I once tried modifying my car lights, and switching from HS1 to H4 was a bit troublesome, depending on the socket compatibility. It's recommended to use the original factory-specified bulb model when replacing to avoid issues like fogging or short circuits.
