LED Lens & Light Distribution for Solar Street Lights
LED Lens & Light Distribution for Solar Street Lights
Short answer: choose the light distribution type first, then pick a lens that delivers it, and verify the pair with an IES file before committing to a purchase order. In a low-power solar fixture the optics are not a styling decision. Every lumen that lands off the road is a lumen the battery paid for and nobody uses. A grid-connected luminaire can compensate for a bad beam with more watts. A 30 W solar fixture cannot.
Lens beam angles: what the T-numbers mean
Each LED is a low-wattage chip, typically 1–3 W, and the total count stays under 100. The lens on each chip sets the beam angle, and the beam angle sets the spread:
| Lens | Beam angle | Where it fits |
|---|---|---|
| T2 | 30°–40°, narrow | Localized road lighting, long throw |
| T3 | ~60°, medium-narrow | Small streets, sidewalks |
| T4 | ~90°, medium-wide | Community roads, parking lanes |
| T5 | ≥120°, wide — up to 360° horizontal | Courtyards and open areas, not roads |
One caution from our production floor: beam angle alone does not decide road performance. A 60° lens throws a soft pool or a hard hotspot depending on the reflector around it.
Batwing and asymmetric lenses: what they fix
Two shapes come up constantly in road work. Batwing lenses put less intensity at the center and more toward the edges, cutting glare while pushing useful light outward — the reason urban streets specify them. Asymmetric (elliptical) lenses stretch the beam along the roadway instead of throwing a symmetric pool; on a narrow street that is the difference between lighting a 12 m strip and lighting a 12 m circle with the rest wasted past the curbs. When a project draws a glare or uniformity complaint, the fix usually starts with one of these two.
IES distribution types: II, III, and V do most of the work
The IES (Illuminating Engineering Society) distribution types describe the pattern the finished fixture throws, and they are the language road-lighting calculations speak:
| Type | Pattern | Typical use |
|---|---|---|
| Type II | Narrow elliptical | Small streets, sidewalks |
| Type III | Medium-wide elliptical | Medium streets, community roads — the most widely used |
| Type V | Circular | Squares, parking lots, courtyards |
Type I, Type IV, and custom asymmetric distributions see limited use in road lighting. Type II, III, and V cover most project specs, so that is the set we keep IES files for — and the set we tell clients to demand.
The lens angle is how you build the distribution type: a T3 lens on a flat panel tends to produce a Type III throw, and a batwing arrangement is how a Type III avoids a hot centerline.
What an IES file tells you — and what to ask a supplier for
An IES file is the standard photometric output of a luminaire: the measured luminous intensity distribution, recorded as intensity curves across the C0–C180 and C90–C270 planes, with peak candela (cd) values and uniformity data. Designers load it into DIALux or AGi32 to calculate road illuminance.
What we tell procurement teams to demand:
- The IES file for the exact fixture being purchased — not a similar model. Lens and LED count differences change the curve.
- Files in every distribution type offered (at minimum II, III, V) so the comparison can be run in-house.
- The intensity curve data, not just a polar plot — the numbers are what the simulation uses.
A supplier who cannot produce these is guessing at your road, and you find out at commissioning.
When the simulation does not match the site: four adjustments
When results disappoint after installation, work through our sequence before replacing fixtures:
- Adjust the lamp head angle. A few degrees of tilt recovers coverage at the far end of the throw — the cheapest fix available.
- Change the lens type or add LEDs. This reshapes distribution and intensity. On a solar fixture, added LEDs cost battery, so try the lens swap first.
- Adjust pole height or spacing. Raising the pole spreads the pool; tightening spacing improves uniformity. Both change the pole's wind load — check our wind load calculator first.
- Re-simulate with updated IES files. Verify the numbers before ordering.
Done well, these adjustments fix most deficiencies without replacing the fixture, on solar and grid projects alike.
How we spec optics for a solar street light project
Classify the area first : road width, lane count, available pole spacing, and whether the priority is throw (a long road) or spread (an open area). Pick the distribution type from that : Type II for narrow streets and sidewalks, Type III for community roads, Type V for squares and parking areas. Wide-beam T5 hardware on a road is a mistake — it lights the windows across the street. Match the lens to the type , then run the IES file in the lighting calculation. Check the energy budget : if the layout only works at 60 W, battery and panel grow with it; if 30 W is the ceiling, tighten spacing or dim after midnight.
Run the numbers yourself with our lighting design tool, or send us the road dimensions. For fixtures with the optics already matched to the LED count, see our all-in-one solar street lights line.
What this guide does not cover
This page covers lens and distribution selection for low-power, DC-coupled solar street lights. It does not cover high-mast or flood lighting, interior lighting, AC-coupled hybrid fixtures, or pole structural design. Performance classes follow IES and EN 13201 practice.