KEY TAKEAWAY
The project conditions should determine the solar lighting configuration.
Most solar street light underperformance traces back to installation geometry rather than to the product. Pole spacing on a continuous road is normally set as a multiple of mounting height, commonly around three to four times the mounting height, and wider where the task is pedestrian or security lighting. The foundation is sized from pole height, head mass, projected wind area, local wind speed and soil bearing capacity, the solar panel needs an unshaded window through the middle of the day facing the equator, and a documented commissioning test is what turns a correct specification into a system that still works in its third winter.
Start with geometry: mounting height, road width and arrangement
Installation geometry is fixed before any hole is dug, because it decides whether the photometric target is achievable at all. Three variables interact: mounting height, pole arrangement across the road, and spacing along it. Changing one without the others usually degrades uniformity even when the average level still looks acceptable.
As a rule of thumb, a single-sided arrangement works when the mounting height is at least roughly equal to the effective width being lit. Staggered arrangements suit widths up to around one and a half times the mounting height, and wider carriageways generally need opposite poles or a central twin-arm pole. These are starting points for a layout, not substitutes for a simulation.
| Arrangement | Typical width it suits | Typical spacing-to-height ratio | Notes |
|---|---|---|---|
| Single-sided | width up to about 1.0 x H | about 3.0-4.0 | Simplest and cheapest; far kerb dims first as width grows |
| Staggered (alternating sides) | width about 1.0-1.5 x H | about 3.0-3.5 | Improves far-side coverage without doubling pole count |
| Opposite (twin sides) | width above about 1.5 x H | about 3.0-3.5 | Two luminaires share each stretch, so each serves half the area |
| Central twin-arm | dual carriageway with a median | about 3.0-3.5 | One foundation serves both directions; heavier pole and base |
| Path or perimeter, spot task | narrow paths, gates, corners | about 4.0-5.0 | Lower level and looser uniformity are usually acceptable |
Spacing-to-height ratio in practice
The spacing-to-height ratio (S/H) is the most useful single number in a layout review. On roads with Type II-M or Type III-M distributions, continuous lighting with acceptable uniformity typically lands in the S/H range of about three to four. An 8 metre mounting height therefore commonly gives spacing in the 24-32 metre band, while a 5 metre pole on a residential lane commonly gives 15-20 metres.
Ratios above about four tend to fail the minimum-illuminance and longitudinal-uniformity criteria even when the average is satisfied, which is the classic cause of a layout that passes on paper and produces dark patches in service. Ratios well below three usually mean the project is buying more poles than the optics require.
What pushes the ratio up or down
Two projects with identical poles can justify different spacing. The variables worth checking before fixing a pole schedule are listed below.
- Optical distribution: a wider Type III pattern generally supports longer spacing than a Type II pattern
- Uniformity requirement: a strict class tightens spacing more than a higher average target does
- Mounting height available: pole height limits set by wind exposure, planning rules or maintenance access
- Overhang and tilt: small changes at the arm move the peak intensity across the carriageway
- Obstructions: trees, bus shelters, signage and building setbacks that block part of the pattern
- Solar constraints: on integrated products the panel orientation follows the luminaire, which can restrict the pole positions
Mounting height and the product range
Published mounting-height ranges are a useful sanity check on a layout. The Reluxlight all-in-one series recommends 4-6 m at 40 W rising to 9-12 m for the 150 W project option, the all-in-two series 4-6 m at 30 W rising to 8-12 m at 120 W, and the split series 5-7 m at 60 W rising to 10-12 m at 200 W. A layout that needs 12 metre poles for a 30 W luminaire, or 5 metre poles for a 200 W luminaire, is usually a sign that the geometry and the product band have drifted apart.
Foundations: what has to be engineered, not guessed
A solar street light pole is not the same structural problem as a grid luminaire on the same pole height. The photovoltaic module adds a large projected wind area high up the pole, and on split systems a battery enclosure adds mass at mid-height. Both increase overturning moment at the base, so a foundation copied from a conventional lighting project can be undersized even when the pole looks identical.
Foundation dimensions therefore belong to a structural calculation for the specific site rather than to a catalogue. What a supplier can provide is the load data; what the project must provide is the ground and wind data.
- Pole height, section, material and base-plate dimensions
- Total head mass: luminaire, panel, bracket and, on split systems, the battery enclosure
- Projected wind area of the panel and luminaire, including the tilt angle in use
- Design wind speed and exposure category for the location
- Soil type, bearing capacity, water table and frost depth
- Anchor-bolt pattern, projection, grade and the required embedment
Cast-in-place base and anchor cage
The common solution is a cast-in-place reinforced concrete base with an anchor-bolt cage set on a template so the bolt circle matches the pole base plate exactly. Set the template level and check it twice: a base plate that has to be forced into position transfers stress into the pole and makes later plumb correction impossible.
Leave the bolt projection specified by the pole drawing, protect the threads during the pour, and keep the top of the concrete slightly above finished grade with a small slope so water drains away from the base plate rather than pooling on it.
Curing, levelling and grouting
Concrete needs to reach adequate strength before a pole with a heavy head is erected on it. The waiting period follows the concrete design and local practice rather than a universal number, and it should be recorded per pole rather than assumed.
Use levelling nuts under the base plate to plumb the pole, then tighten the top nuts to the specified torque in a diagonal sequence. Where the pole drawing calls for non-shrink grout under the plate, leave a drainage path or a weep so trapped water can escape.
Ducts, drainage and earthing
Even an off-grid pole usually needs a duct: split systems route panel and battery cabling, and many projects later add sensors, cameras or communication modules. Install a spare duct at the pour stage, seal both ends against water and vermin, and keep the entry above any expected standing-water level.
Earthing and surge protection should follow the local electrical code for outdoor lighting structures. Poles carrying photovoltaic modules on exposed ground are lightning-exposed structures, and a surge event on the panel side normally destroys the controller first, so the earthing detail deserves the same attention as it would on a grid installation.
Panel orientation, tilt and shading
Charging performance is decided by the panel's orientation and by what stands in front of it, and neither is recoverable after installation without returning to site. In the northern hemisphere the panel faces true south, in the southern hemisphere true north, and near the equator the azimuth matters less than the shading survey.
Set azimuth against true north, not magnetic north. Magnetic declination reaches many degrees in some regions, and a compass reading used without correction is a common cause of a whole street being aimed slightly wrong.
Tilt selection
A common starting point is a tilt roughly equal to the site latitude, adjusted upward when winter performance governs the design, because a steeper panel favours the low winter sun. In the tropics the tilt band is shallow, but it should stay steep enough for rain to run dirt off the glass rather than leaving it to dry in place; a low single-digit tilt tends to soil quickly.
The all-in-two series supports a 0-60 degree panel tilt range and the split series mounts the module independently, so both allow the panel to be aimed for the solar resource rather than for the road. On integrated all-in-one products the panel travels with the luminaire, so orientation has to be checked at the layout stage while pole positions can still be adjusted.
Shading survey
Shade costs disproportionately more than its apparent area suggests, because a partly shaded module can lose a large share of its output. Survey each pole position rather than the street as a whole.
- Check for shade across the middle of the day, roughly the 9:00 to 15:00 window, in the worst season
- Include tree growth over the next three to five years, not just today's canopy
- Watch for buildings, walls, signage, adjacent poles and overhead cables
- Note dust, salt or industrial fallout that will accelerate soiling
- Record any position that cannot be cleared, so it can be re-sized or moved rather than quietly underperforming
Mechanical and electrical installation practice
The details in this section are where an installation either keeps or loses its ingress protection rating. A luminaire rated IP66 with IK10 impact resistance, as the all-in-one and split street-light series are, only performs to that rating if the housing is left intact and the cable entries are made with the correct glands.
- Never drill or file the housing to pass a cable; use the provided entries and rated glands
- Tighten glands onto the correct cable diameter and leave a drip loop below every entry
- Torque bracket and pole-top fasteners to the specified values; use the supplied anti-loosening hardware
- On split systems, size the panel-to-controller and battery-to-luminaire runs for voltage drop, not just for current
- Keep the battery enclosure ventilated as designed, out of standing water and out of direct all-day sun where possible
- Fit tamper-resistant fasteners where theft or vandalism is a known risk, and record the tool type in the handover pack
- Do not mix battery types or capacities within one system, and do not extend a factory harness without agreement
Temperature and placement
Battery life is temperature-sensitive, and the all-in-two and split series specify a working range of -25 to 65 degrees Celsius. Within that range, cooler is better for the pack: an enclosure that sits in full afternoon sun against a dark wall will run hotter than the same enclosure shaded by the pole.
In hot climates, prefer placements that see some shade in the afternoon, keep enclosures off heat-reflective surfaces, and leave the designed air gap behind panel and enclosure rather than clamping them flat against a structure.
Commissioning: the acceptance test that prevents callbacks
Commissioning is a measurement and recording exercise, not a look at the light. A short, standard test per pole, with the results written down, is what makes a warranty conversation factual later and what catches wiring and programming errors while the crew is still on site.
| Step | What to check | What to record |
|---|---|---|
| 1. Mechanical | Plumb, bolt torque, bracket security, panel tilt and azimuth | Tilt angle, azimuth, torque confirmed |
| 2. Panel | Open-circuit voltage and short-circuit current in daylight, polarity | Voc, Isc, time of day, sky condition |
| 3. Battery | Resting voltage before commissioning, connector seating | Pack voltage and capacity as installed |
| 4. Controller | Programmed profile, dimming steps, sensor mode | Profile written to the pole record |
| 5. Night simulation | Cover the panel to trigger switch-on; confirm full output and each dim step | Pass or fail per step |
| 6. Sensor | Walk or drive the detection zone; check hold time and standby level | Detection distance, hold time, standby level |
| 7. Identity | Serial numbers of luminaire, controller, battery and panel | Serial numbers against pole ID |
| 8. Geometry | Photograph the pole in context with the layout reference | Photo filed against pole ID |
- Test at least one pole per circuit or per delivery batch in full, and every pole for switch-on and profile
- Commission with the panel covered rather than waiting for dusk; it is faster and repeatable
- Confirm that a pole reaching a low state of charge behaves as designed instead of switching off unpredictably
- Reset any pole whose battery was allowed to sit discharged during storage before judging its performance
Handover documentation and the first-month review
The value of commissioning records appears months later. A handover pack that lists what was installed, where and with which settings turns a vague performance complaint into a specific, solvable question, and it is also what allows a second contractor to service the site without guesswork.
Plan a short review after the first few weeks of operation, ideally including a spell of poor weather. Compare the observed behaviour against the design profile and the expected recharge pattern, and adjust the profile before the season changes rather than after complaints arrive.
- Pole schedule with positions, heights, arrangement and spacing as built
- Model, wattage, battery capacity, panel size and serial numbers per pole
- Programmed control profile and sensor settings per pole
- Commissioning results, including panel readings and night-simulation outcomes
- Datasheets, installation instructions and the spare-parts list
- Named contact and procedure for reporting a fault
Common installation mistakes
Almost every recurring field problem in solar street lighting comes from a short list of avoidable causes. Reviewing this list at the pre-installation briefing is cheaper than revisiting a street.
- Spacing set by pole availability or by the previous project rather than by the mounting height and optics
- Panels aimed with an uncorrected compass, or set flat enough to hold dirt
- Shading measured at the time of the site visit only, ignoring season and tree growth
- Foundations reused from a grid-lighting standard that never accounted for the panel's wind area
- Housings drilled on site, destroying the ingress rating that the specification paid for
- Controllers left on factory defaults when the project specified a different profile
- Batteries stored discharged for weeks before installation and then judged as faulty
- No record of settings or serial numbers, making later diagnosis guesswork
FREQUENTLY ASKED QUESTIONS
Questions buyers ask before configuration
How far apart should solar street lights be installed?
Spacing is normally derived from mounting height rather than fixed in metres. On roads with Type II-M or Type III-M distributions, continuous lighting with acceptable uniformity typically falls in a spacing-to-height ratio of about three to four, so an 8 metre pole commonly gives 24-32 metres and a 5 metre pole 15-20 metres. Paths and security-only tasks can go wider. Confirm the final layout with a photometric simulation.
What tilt angle should the solar panel be set to?
A common starting point is a tilt close to the site latitude, increased somewhat where winter performance governs the design. Keep enough tilt for rain to wash dirt off the glass rather than leaving it to dry in place. The all-in-two series supports a 0-60 degree tilt range and the split series mounts the panel independently, so both allow the panel to be aimed for the solar resource rather than for the road.
How big does the concrete foundation need to be?
It has to be calculated for the site, not copied from a catalogue. The inputs are pole height and section, total head mass, the projected wind area of the panel and luminaire at the tilt in use, the design wind speed and exposure, and the soil bearing capacity. Solar poles carry more wind area than a grid luminaire of the same height, so a foundation borrowed from a conventional lighting project is often undersized.
Can a solar street light be installed on an existing pole?
Sometimes, but it is a structural question rather than a bracket question. The pole and its foundation have to accept the extra mass and wind area of the panel and, on split systems, the battery enclosure. Check the original pole capacity, the base condition and the available unshaded orientation before assuming a retrofit is possible.
How do I test a solar street light during the day?
Cover the solar panel so the controller sees darkness and switches the luminaire on, then step through the programmed profile. This is faster and more repeatable than waiting for dusk, and it lets the crew verify dim steps, sensor response and hold time while still on site.
Which way should the solar panel face?
True south in the northern hemisphere and true north in the southern hemisphere, corrected for magnetic declination if a compass is used. Near the equator the azimuth is less critical than keeping the panel free of shade through the middle of the day, so prioritise the shading survey over a few degrees of aim.