Start with autonomy, not wattage
The headline wattage of a solar street light tells you how bright it is on a good day. Autonomy tells you whether it will still be lit during the rainy season — and that is the number that generates complaints from end users.
Autonomy is the number of consecutive nights the light runs at rated output with no solar input at all. Ask for it in nights, and ask which output profile it assumes. A light quoted at 5 nights autonomy using motion-sensing dimming is not the same product as one quoted at 5 nights at full output.
The seven specifications to check
The table below is the checklist we use internally when reviewing a customer specification. If a supplier cannot answer any of these in writing, the quotation is not comparable to ours.
| Specification | What good looks like | What to watch for |
|---|---|---|
| Battery chemistry | LiFePO4 with a published cycle life | Lead-acid quoted as "gel" with no cycle data; capacity that collapses above 40 °C |
| Usable battery capacity | Stated in Wh, with depth of discharge given | Ah figures at 3.2 V presented as if they were at 12 V |
| Autonomy | Nights at rated output, with the dimming profile named | Autonomy quoted with motion dimming but sold as continuous output |
| Luminous flux | Delivered lumens (lm) after optics and diffuser losses | LED chip lumens before losses, which can overstate output by 25–35% |
| Solar array | Wp of monocrystalline panels plus the peak sun hours assumed | Array sized for 5 peak sun hours sold into a market with 3.2 |
| Ingress protection | IP66 for the luminaire, IP67 or better for the connector | IP65 claimed for coastal or dusty sites |
| Thermal derating | A stated maximum ambient temperature and the derating curve | No derating data for sites that regularly exceed 45 °C |
Sizing by road class
Pole height and spacing should follow the road class, not the available budget. Over-spacing is the single most common installation error we see in distributor feedback, because it is invisible in the daytime.
| Road type | Pole height | Recommended LED power | Typical spacing |
|---|---|---|---|
| Residential street, 2 lanes | 5–6 m | 40–60 W | 20–25 m |
| Collector road, 2 lanes | 6–8 m | 60–90 W | 25–30 m |
| Arterial road, 4 lanes | 8–10 m | 120–150 W | 30–35 m |
| Parking area or plaza | 6–8 m | 60–100 W | 15–20 m |
| Park path or campus walkway | 3–4 m | 15–25 W | 8–12 m |
Derate for climate before you compare prices
A solar light is an energy balance, and both sides of the balance move with temperature. Panel output falls about 0.4% per degree above 25 °C cell temperature, while lithium capacity and cycle life also decline in sustained heat.
Applying the adjustments below usually changes the required array size by 30–60% between markets, which is exactly why a single global specification does not work.
| Climate | Panel sizing | Battery | Notes |
|---|---|---|---|
| Temperate (Central Europe) | Base × 1.0 | Standard LiFePO4 | Low winter yield, plan for 2 nights autonomy |
| Hot and dry (Gulf, Sahel) | Base × 1.25 | High-temperature LiFePO4 | Add dust cleaning interval, ventilate the battery box |
| Hot and humid (West Africa, SE Asia) | Base × 1.4 | High-temperature LiFePO4 | IP66 minimum, corrosion-resistant fasteners |
| High altitude or cold | Base × 1.15 | Heated or insulated enclosure | Charge protection below 0 °C |
What the lowest quotation usually omits
- A named battery cell supplier and a cycle-life test report.
- The assumed peak sun hours, which is what the whole array sizing depends on.
- IP rating of the cable connector, not just the luminaire.
- The dimming profile, so an "8-hour" runtime can mean 8 hours at 30% output.
- Spare controllers and drivers, which are the parts that fail first.
- A packing list keyed to HS codes, which slows down customs clearance.
Frequently asked questions
01How many watts do I need for a 6-metre pole?
02Is a higher wattage always better?
03Why do cheap solar lights fail in the second year?
Send us your requirement, get a sized quotation in 24 hours
Tell us the destination country, target quantity and what the product must do. We come back with a model, a price and the lead time.
