After years in foreign trade, one of the most frequent protection questions from clients is: "Is your street light IP65 or IP66? Can it be submerged in water?" Many people assume that a higher number is automatically better, or that IP67 means the luminaire can stay underwater indefinitely. In actual street-lighting applications, the differences are more nuanced; choosing the wrong rating is not just a matter of extra cost-it directly affects whether the fixture can survive heavy rain and temporary flooding. This article clarifies the real differences between IP65, IP66, and IP67 for street lights.
Basic Meaning of the IP Rating
IP stands for Ingress Protection and consists of two digits. The first digit indicates protection against solid objects (dust); the second indicates protection against liquids (water). The commonly used street-light ratings IP65, IP66 and IP67 all begin with 6, meaning they are completely dust-tight. The real differences lie in the second digit.
IP65 protects against low-pressure water jets. The test uses a 12.5 L/min jet from all directions, simulating ordinary rain and spraying. IP66 protects against powerful water jets. The test volume rises to 100 L/min at higher pressure, covering heavy rain, typhoon-driven rain, and even high-pressure hose cleaning. IP67 protects against temporary immersion. The luminaire is fully submerged in 1 metre of water for 30 minutes and must not suffer water ingress that affects function.
Key Differences in Actual Street-Light Applications
Most road luminaires are mounted 6–12 m high and primarily face rainfall and wind-driven rain rather than submersion. Therefore IP65 is already sufficient for the majority of urban and campus roads; it keeps out everyday rain and dust. Many export projects use standard IP65 street lights that perform reliably for years.
IP66 is better suited to coastal areas, typhoon-prone regions and locations with frequent intense rainfall. The impact of strong wind-driven rain is far greater than ordinary rain, so sealing structures and any ventilation openings must be more robust. On several projects in Southeast Asia and coastal South America, clients initially chose IP65; after typhoon seasons some fixtures showed water ingress. Switching to IP66 noticeably reduced the problem. IP66 is also preferable for industrial or port areas that require regular high-pressure washing.
The advantage of IP67 is its ability to withstand short-term immersion. On low-lying roads, flood-prone sections, under bridges or near underpasses, heavy rain can cause temporary ponding that submerges the lower part-or even the entire body-of the luminaire for a period. In these cases IP65 and IP66 offer no guarantee against water entry, while IP67 is designed for the situation. Note, however, that IP67 only covers temporary immersion (standard conditions: 1 m depth for 30 minutes). It is not intended for continuous underwater use. Permanent submersion requires IP68, a rating rarely applied to conventional street lights.
Can They Be Submerged? Direct Answers
IP65: Cannot be submerged. It only resists jets; immersion carries a high risk of water entry. IP66: Likewise cannot be submerged. It withstands stronger jets than IP65 but has no immersion test or guarantee. IP67: Can withstand short-term immersion (1 m for 30 minutes under standard conditions), but not prolonged submersion and is not a diving light.
The biggest misconception is equating "waterproof" with "can stay underwater indefinitely." An IP rating only confirms that the product passed specific laboratory tests. Real-world performance also depends on ageing of seals, design of breathing valves, mounting angle and long-term thermal expansion/contraction. A poorly designed IP67 can be less durable than a well-engineered IP65.
Selection Advice for Export Projects
Do not choose solely by the higher number. First clarify the project climate and mounting location: ordinary urban road, coastal typhoon zone, or low-lying flood-prone section. IP65 is adequate for ordinary roads; prioritise IP66 in strong-rain and wind areas; move to IP67 only when there is a clear risk of temporary flooding. Always request a third-party IP test report rather than relying on brochure claims.
Pay equal attention to overall construction. Any weak point-heat-dissipation openings, driver compartment, lens sealing surface-can render a high IP rating meaningless. In our proposals we state the recommended rating together with the reasons, and we remind clients about correct installation and maintenance to avoid later batch failures caused by water ingress.
An IP rating is not a case of "higher is better" but of "more appropriate is better." Street lights spend most of their life facing rain and wind, not swimming-pool conditions. Matching the real operating environment to the test standard ensures reliability without unnecessary cost.
If you are working on an overseas street-lighting project and are unsure whether to specify IP65, IP66 or IP67, feel free to share the project location, road type and any flood risk. We can recommend the appropriate protection level based on actual conditions and help you verify whether the manufacturer's test reports are reliable.
