Solar street light enquiries from Africa and the Middle East come back with quotations marked 100W or 200W. What that number describes varies by factory: lamp power, panel power, or simply a model name.
Unpack it. A solar street light has four parts, panel, battery, controller and LED module. How long it stays lit is set by battery capacity in watt-hours, not amp-hours, because the same 100Ah represents very different energy at different system voltages.
Take a real case: 60W of LED, twelve hours a night, needs 0.72 kWh. With three consecutive overcast days of autonomy, the battery must hold about 2.2 kWh. Products marketed as 100W often carry 0.3 to 0.6 kWh. The gap shows up on the first cloudy day.
So ask for three numbers directly: battery in Wh, panel in W, and measured lumens from the LED module. If the three do not reconcile, the wattage label means nothing.
Ask about chemistry too. Ternary lithium is cheap with high energy density, but thermal runaway risk makes it a poor match for Gulf heat. LiFePO4 costs more, cycles longer and holds up better at temperature, the right choice for outdoor projects.
Controllers split into PWM and MPPT. MPPT charges 10 to 30 percent more efficiently, which shows on overcast days. Cheap units use PWM.
Two engineering parameters get skipped. Wind load rating, which comes down to how the head attaches to the pole. And ingress protection, IP66 at minimum, with dust structure considered for sandy regions.
Warranty is the final filter. Three years on the fixture with one year on the battery is a different cost structure from three years on both. Around 80 percent of solar street light failures trace to the battery, so the battery warranty is the real quality statement.
On these projects we size the system from the customer's actual sun hours and overcast days, rather than ordering off a factory model list.