Solar yard lighting removes the cheapest kWh on your CFE bill
Perimeter, yard and parking lighting at a Mexican industrial site runs at night. On a time-of-use tariff, most of those hours fall in the base period, the cheapest energy on the schedule, and the peak that sets the demand charge is almost always established by daytime process load. Take that lighting off the meter with self-contained solar poles and you remove the least expensive kilowatt-hours the site buys, while the demand charge stays where it was.
That is not an argument against solar lighting. The number that makes an off-grid pole competitive at an industrial site in Mexico is the avoided civil work, the trenching, conduit, cabling and switchgear needed to reach a light point that sits far from the nearest panel board. The energy saving is real and it is small. The installation saving can be the whole project.
This piece covers specification and siting: how the choice between off-grid and grid-tied changes the regulatory paperwork, which NOM standards the luminaire has to meet, what determines whether a pole still lights in February, and where a control layer pays for itself. For the case on carbon and the shift in installed cost that made these systems viable, see the companion piece on what changed in solar lighting economics.
Read your tariff before you price the saving
Sites on medium-tension supply with demand of 100 kW or more are billed under GDMTH, the time-of-use class with base, intermedio and punta periods. Below 100 kW on the same voltage band the class is GDMTO, a flat rate. Larger loads taken at subtransmission voltage sit on DIST, and at transmission voltage on DIT. All of them bill energy and demand separately, and lighting sits almost entirely on the energy side.
One check is worth making before anyone builds a model. The punta window is defined by region and by season in the CFE tariff schedule approved by CRE, and in several regions it falls in the evening. Exterior lighting energized at dusk can therefore land inside punta for part of the year, which raises the value of removing it and also raises the value of simply rescheduling when it switches on. Pull the applicable period definition for your region and season from the current schedule rather than assuming night means base.
Any savings range quoted for a lighting project is measured against current CFE supply and varies with tariff class, region, load factor and consumption profile. Treat it as illustrative until 12 months of billing and, where the meter provides it, interval data have been reviewed for the site.
Off-grid and grid-tied are two different regulatory objects
A self-contained pole carrying its own panel, battery and controller does not connect to the Red General de Distribución. It has no interconnection contract, no meter and no CRE registration, and it is invisible to the distributed generation regime. That is the main administrative advantage of the format and it is frequently the reason a facilities team can proceed without a permitting cycle.
An array on a roof or on the ground that feeds the site's lighting circuits through the main service is a different object. It interconnects, and the distributed generation rules apply: the SENER Manual de Interconexión published in the Diario Oficial de la Federación on 15 December 2016, and CRE resolución RES/142/2017 published in the DOF on 7 March 2017, which govern Centrales Eléctricas with capacity below 0.5 MW connecting to the distribution network. Two points are routinely misunderstood. The 0.5 MW figure is generating capacity, expressed in MW, and it is not the facility's load and not the array's DC peak in kWp. And under medición neta, the default modality, surplus generation is credited against future consumption for up to twelve months rather than sold to CFE. Only under venta total is output actually purchased, at Precio Marginal Local values, and facturación neta values generation and consumption separately at hourly market prices.
What the luminaire has to comply with
Exterior LED luminaires for roads and public outdoor areas are covered by NOM-031-ENER-2019, published in the DOF on 3 March 2021 and in force from 31 May 2021, which sets energy efficiency requirements and test methods and supersedes the 2012 edition. Road lighting systems as installations are covered by NOM-013-ENER-2013, published in the DOF on 14 June 2013 and in force from 12 October 2013. Interior lighting in non-residential buildings falls under NOM-007-ENER-2014, published on 7 August 2014 and in force from 5 December 2014, with CONUEE as the responsible authority.
Ask the supplier for the conformity certificate against the specific catalog number being quoted, not for a statement that the product family complies. Substitutions between quotation and delivery are common in this category, and a certificate for a sibling model is not evidence about the unit that arrives on the pallet.
Siting decides whether the light is still working in February
An off-grid light fails quietly. There is no breaker to trip and no bill to rise, so a poorly sited pole simply goes dark and stays dark. The variables that decide this are physical and they are checkable in advance.
- Autonomy, sized on consecutive poor days rather than an annual average. The design question is how many successive low-irradiance days the battery has to carry, using the worst month for the specific location, not the site's yearly mean.
- Shading through the year. Buildings, stacks, silos, cranes and mature trees cast different shadows in December than in June. Check the winter sun path, not the summer one.
- Ambient temperature at the battery. Battery service life falls as operating temperature rises, which is the binding constraint on pole-top enclosures in Sonora, Baja California and the Bajío in summer. Ask where the battery sits on the pole and how it is ventilated.
- Soiling. Cement, aggregates, mining, agricultural and unpaved-yard environments coat a panel quickly, and a soiled panel is an undersized panel. Cleaning frequency belongs in the operating budget from the start.
- Wind loading and foundation. A pole-mounted panel is a sail, and the foundation specification for a solar pole is not the same as for a plain luminaire on the same site.
- Theft and vandalism exposure. Perimeter and remote poles carry a battery worth stealing. Enclosure design and mounting height are a security decision, not only a maintenance one.
Where the control layer earns its cost
The most valuable networked function on an off-grid installation is not dimming. It is fault reporting. Because these poles are electrically isolated, nobody at the site learns that a unit has failed until someone walks past it at night, and the distinction between a failed LED module, a degraded battery and a faulty charge controller decides which technician goes out and with what part. A controller that reports state of charge, output and fault code by unit converts an unscheduled discovery into a scheduled visit.
Adaptive output is the second function that pays, and it pays through the battery rather than through the bill. Reducing output when ambient light is sufficient, or when no one is present, cuts the nightly energy draw, which allows a smaller battery and a smaller panel for the same autonomy. That is a capital saving at the specification stage, and it is worth quantifying before the equipment is ordered rather than after.
Group scheduling matters for sites with seasonal or shift-driven vacancy, since a section can be dimmed or deactivated for a shutdown and restored without a truck. Sun-tracking mounts, remote tilt adjustment, public Wi-Fi, air quality sensing and parking detection are all available on these platforms. None of them belongs in an industrial specification unless a named person at the site owns the resulting data and has a use for it, and each one adds a failure mode to an asset whose main virtue is that it has very few.
Before you specify
- The distance from each proposed light point to the nearest usable panel board, and the installed cost per meter of the trenching and cabling it would replace. This is the number the business case turns on.
- The tariff class, and the punta period definition for your region and season, so the energy saving is valued correctly rather than assumed to be base-period energy.
- Whether the design is off-grid or interconnected, since only the second brings the CRE distributed generation process with it.
- NOM-031-ENER-2019 conformity for the exact luminaire model quoted.
- Battery chemistry, expected replacement interval at the site's actual ambient temperature, and who holds that replacement cost over the contract term.
- The fault reporting path: what the system reports, to whom, and what the response commitment is.
Where a site is also looking at metering the loads that remain on the CFE meter, the same review covers both. See how monitoring separates consumption from billed demand.
Request a lighting specification and siting review
Mexico Energy Partners reviews exterior and interior lighting projects at Mexican industrial and commercial sites against the applicable NOM standards, the site's tariff class and the civil work each light point would otherwise require. An initial review needs a site plan with proposed light points, 12 months of CFE billing, the tariff class, and the existing lighting schedule with mounting heights.
See how our energy efficiency assessments work or request a preliminary lighting assessment.