Lumeitalia
A long-term evaluation model for urban street lighting investments: cost items, assumptions and sensitivity.
The cost of a lighting installation is spread over a long horizon, where the initial investment often weighs less than energy and maintenance combined. The urban road network is the largest lit infrastructure managed by Italian municipalities and accounts for the biggest share of municipal energy spending. This Centro Studi Lumeitalia white paper proposes an evaluation model applicable to urban street lighting interventions.
The regulatory reference for urban street lighting is not a single document but a coordinated set of standards covering performance, safety and environmental impact. In design practice the following documents drive the main choices.
The model considers five items: initial investment (supply, installation, ancillary works), energy consumption over the period, planned maintenance, corrective maintenance and replacements, end-of-life management. Excluding an item is legitimate only if declared: a comparison ignoring maintenance systematically favours the least accessible solutions.
Three assumptions dominate the outcome: energy price, operating hours and failure rate. The model should always be presented with a sensitivity analysis on these variables, showing how the result shifts under conservative and optimistic scenarios. A single figure with no range communicates a precision the model does not have.
For urban street lighting, the cost component tied to luminaire accessibility must also be considered: two solutions with the same failure rate can have very different intervention costs.
The model exists to make assumptions explicit, not to produce a definitive number. In a comparison, the spreadsheet with visible assumptions should be shared so each party can substitute its own values and test the robustness of the conclusion. That transparency is what makes the decision defensible before an audit body.
The difficulties that most often emerge in urban street lighting projects are not about product selection, but about defining requirements and verifying results.
An orderly method drastically reduces variations during works and disputes at commissioning. Three choices make the difference from the earliest stages.
Non-conformities found at commissioning almost always come from three causes: requirements not declared or declared without a reference standard, calculation run on idealised geometry, and an optimistic maintenance factor. All three can be avoided at zero cost during design.
A urban street lighting project holds up over time when requirements are declared, the calculation reproduces real conditions and on-site verification follows an agreed protocol. Component selection matters, but comes later: without measurable requirements even the best product delivers a result that cannot be demonstrated. Centro Studi Lumeitalia makes its technical office available to review requirements and design checks.
Methodological note: This content is written for technical information purposes by Centro Studi Lumeitalia and does not replace the lighting design or a full reading of the standards cited. Applicable performance values are those of the standards in force at design time.
The designer, through the risk analysis required by UNI 11248, based on traffic, vulnerable users, visual complexity and accident rate.
Yes. UNI 11248 allows adaptive regulation when risk parameters change, provided the profile is documented in the design and verifiable at commissioning.
From a written definition of performance requirements and verification conditions: this step drives every later choice and makes the result either disputable or defensible at commissioning.
Photometric files of the proposed luminaires, declaration of conformity, lifetime data declared per IES LM-80 with its conditions, the maintenance schedule and warranty terms.