Common Mistakes in Solar Street Lighting Tenders

Mistake one: specifying watts instead of light

“100 W solar street light” survives in tender documents because it is quick to write and quick to price, but it describes an input rather than the result being purchased. Two luminaires with the same nominal power can differ substantially in delivered lumens once LED efficacy, optical efficiency, lens transmission and driver losses are counted, so a lower-powered but better-optimised unit can comfortably out-light a cheaper high-wattage one at the same road surface. Write the requirement downward from the road instead: a lighting class, an average maintained illuminance, a uniformity ratio, and a distribution described by a photometric file rather than by wording such as “wide beam”. Wattage then becomes a consequence of the design rather than an input to it. The same discipline applies to every adjective — “high brightness”, “long life” and “maintenance free” cannot be tested, so each should become a number, a standard or a document.

Mistake two: autonomy quoted without a solar resource

“Three days of autonomy” looks like a firm criterion but on its own is half a sentence. Autonomy describes how long the battery alone can carry the load through days of effectively no useful charging, so it depends entirely on the site. Three days where the worst month yields 3.0 peak sun hours is a very different design from three days at 4.8, and a bidder who quietly sizes panels against an annual average can still claim three days on paper while running short every wet season. Require the assumed worst-month daily peak sun hours to be declared for a named location, together with the charge-path efficiencies used, the nightly load in watt-hours. See battery autonomy sizing for the arithmetic.

Mistake three: buying nameplate amp-hours

Quoting a battery as “100 Ah” tells the buyer very little, because usable energy depends on chemistry, depth of discharge and temperature. The same block delivers 80 Ah of usable charge at 80% depth of discharge and 50 Ah at 50%, and a lead-acid unit rated at a 20-hour rate delivers less again when the load empties it in five hours. Temperature discounts it further in a cold enclosure, while heat accelerates ageing in a sun-facing metal compartment. A clause is therefore incomplete unless it names the chemistry, nominal voltage, allowed depth of discharge, end-of-life capacity criterion — commonly 70% or 80% of rated capacity — the operating temperature range inside the compartment, and the safety standard the pack is type-tested against, such as IEC 62133.

Mistake four: treating the dimming profile as a detail

A 60 W luminaire over ten hours is not a 600 Wh load. At full output for four hours, 50% for three and 30% for the remaining three, it is (60 × 4) + (30 × 3) + (18 × 3) = 384 Wh — a reduction of more than a third that changes the panel and battery requirement completely. A tender that says only “lighting hours: ten” forces every bidder to invent a profile, and the cheapest bid will invent the most aggressive one and still pass. Fix the profile in the document, with the fraction of full output in each period and the daily total in watt-hours, and state that it is a measurable performance requirement. The energy consequences are covered in dimming profiles and motion sensing.

Mistake five: a lump-sum price with no breakdown

A tender asking for one price per pole cannot be evaluated, because the components inside that price are exactly what varies between bidders. Ask for the price split by luminaire, panel, battery, controller, pole, foundation, cabling, freight and installation, and require the bill of materials line numbering to match the price schedule so quotations can be compared row by row. The split also makes substitution visible: when the battery is its own priced line, swapping a lithium pack for a smaller lead-acid one between award and shipment leaves a trail. Normalising bids this way is mechanical once the rows exist, as described in making quotes comparable.

Mistake six: documents and inspection left as extras

Photometric reports with IES or LDT files, module and battery type-test reports, the lighting calculation for each road type, general arrangement and foundation drawings, and the controller setting sheet are all produced by the manufacturer. They are the only way to verify that what was promised was delivered, and they are the first items a cheap bid leaves out. Make them contractual deliverables with a deadline before shipment, and require each to name the offered product rather than being a generic document with the model number added by hand. Add the right to inspect before loading and to witness loading, plus a commissioning record of the settings actually used on site — clock coordinates, profile steps, disconnect thresholds, sensor sensitivity. Without those, the first fault of the rainy season becomes an argument rather than a maintenance call. A worked set of checks is in the pre-shipment inspection checklist.

How we can help

We are a China-based trading and project sourcing company, not a manufacturer. We review specifications and BOQs, match a product and configuration to your site conditions, source from qualified manufacturers, and manage quality through to pre-shipment inspection.

• Read your draft tender and list the clauses that cannot be measured or verified.
• Re-draft weak clauses into numerical requirements covering light, energy, battery and documentation.
• Build a bid-comparison sheet from your own bill of materials rows.
• Arrange pre-shipment inspection against the specification, reporting to you rather than to the supplier.

If you are preparing a tender or specification and want a second opinion, contact us.