An energy audit at a Mexican plant is a measurement exercise aimed at one document, the CFE invoice. For most industrial sites that invoice is GDMTH, GDMTO, DIST or DIT, and it is not a single price. CRE set the methodology for those classes in Acuerdo A/058/2017 of 23 November 2017, and the schedules applied from 1 December 2017 came from Acuerdo A/061/2017 of 29 November 2017. Each bill splits into an energy charge, a capacity charge, distribution, transmission, a CENACE operation charge, a basic supply operation charge and connected services.

That split is why one savings percentage cannot describe the work. Cutting kilowatt hours moves the energy charge and leaves the capacity charge untouched. Shifting load out of the punta window moves both. Correcting power factor removes a surcharge computed on the amount of the invoice rather than on consumption. Three findings, three different lines, three different payback profiles.

The decision here is narrow. Before your next contracted demand review, do you commission a measured audit, or keep negotiating a figure you cannot decompose? What follows is what the measurement attaches to on a Mexican bill.

What the invoice is made of

GDMTH covers medium tension users above 25 kW of monthly demand with hourly metering. Under the structure A/058/2017 established, the energy charge is differentiated by period, base, intermedio and punta. The capacity charge is set on maximum coincident demand during peak periods. Distribution and transmission are assigned by tension level. The CENACE operation charge and connected services charges vary with consumption, and the basic supply operation charge is fixed per user.

Read that list against your own bill before commissioning anything. A plant on GDMTO has no hourly energy split, so a load-shifting measure that pays for itself on GDMTH may never pay back at all. A site billed on DIT sits at transmission voltage and its distribution component behaves differently again. The tariff class decides which measures are worth metering, which is why the tariff review comes before the plant walk-through rather than after it.

Three findings that move three different lines

The first is consumption. Compressed air leaks, motors running unloaded, chillers holding a setpoint nobody has revisited, lighting on through shifts that ended years ago. All of these reduce kWh. On an hourly tariff they reduce it unevenly, because a kilowatt hour removed at 20:30 is worth more than one removed at 03:00.

The second is demand. The capacity charge follows maximum coincident demand in the peak periods, so it is set by coincidence rather than by total use. Two compressors starting inside the same interval can carry a capacity charge for the rest of the month. This is the finding that most often survives a plant's own internal review, because nobody sees it without interval data. Submetering and energy monitoring are what turns it from an argument into a measurement.

The third is power factor. Under the acuerdo published in the DOF on 31 October 2000, the surcharge applies when the billing period average falls below 90% lagging, and it is charged as a percentage of the invoice amount. The surcharge is capped at 120% and the corresponding bonus at 2.5%. The base matters more than the cap. Because the charge is computed on the amount of the bill rather than on kilowatt hours, it does not shrink when production does. A plant that halves output and leaves its reactive load uncorrected pays a larger share of a smaller bill.

Where an audit feeds a legal obligation

Two obligations in force in September 2023 give the same measurement a second job.

A site whose installations consumed more than 45 GWh of electricity in the previous calendar year is a Usuario de Patrón de Alto Consumo. So is one that burned more than 100,000 barrels of oil equivalent in fuels other than transport fuel. The criteria were published in the DOF on 15 November 2018. Those users report their energy information to CONUEE between 1 March and 30 June each year, covering production, consumption by fuel, and the efficiency measures implemented with their energy and economic results. An audit does not discharge that duty. It produces the data the filing needs, which is a different and more modest claim than the one usually made for it.

The second is the Código de Red. CRE issued it as RES/151/2016, published in the DOF on 8 April 2016, and reissued it as RES/550/2021, published on 31 December 2021 and in force from 1 January 2022, repealing the earlier resolution. It places obligations on centros de carga, and the studies behind compliance draw on the same electrical measurements an audit collects. Commissioning one measurement campaign for both costs less than commissioning two.

The thresholds people confuse

Three separate thresholds get mixed together in conversation, and mixing them sends the wrong plants toward the wrong process.

• Usuario Calificado. 1 MW of maximum demand at a centro de carga over the previous twelve months is the level at which a load can register with the regulator and buy from a Suministrador Calificado.
• Direct participation in the Mercado Eléctrico Mayorista. 5 MW together with 20 GWh a year, under the Manual de Registro y Acreditación de Participantes del Mercado published by SENER in the DOF on 15 July 2016.
• Usuario de Patrón de Alto Consumo. More than 45 GWh of electricity a year, under the criteria published in the DOF on 15 November 2018.

Demand is measured in megawatts. Consumption is measured in megawatt hours or gigawatt hours. A recommendation expressed in megawatts of consumption identifies nobody, and a recommendation pinned to five megawatts excludes most of the plants that would benefit from the exercise.

None of the three thresholds gates an audit in any case. An audit is worth commissioning at whatever load the capacity charge, the punta energy charge or the power factor adjustment is large enough to fund the measurement, and that is a question about your invoice rather than about your registration status. Readers weighing the supply side at the same time should treat qualified supply as a separate decision, because it changes who bills you and not what you consume.

What an audit delivers

The deliverable is concrete. A measured load profile by system and by shift, taken with logging equipment installed on feeders rather than inferred from nameplate ratings. A ranked list of measures, each with capex, the invoice line it moves, and simple payback. A tariff and load factor review that says whether the plant is on the right class. A baseline against which any later claim of a saving can be verified.

What an audit cannot deliver is a percentage before the measurement. Any figure offered before a logger has been on the switchgear comes from somebody else's plant. Mexico Energy Partners publishes no savings range for that reason. A plastics plant on GDMTH in Querétaro and a cold store on GDMTO in Sonora do not share a measure list, and they do not share a split between electricity and fuel either.

That split is worth stating plainly. A boiler or steam measure reduces gas, not electricity, and it does not move the CFE invoice. Reporting one as the other is a measurement error before it is a savings error. Sequencing the work by invoice line is the discipline behind best practices for energy efficiency in Mexico.

One more thing an electrical measurement surfaces. A motor drawing above rated current under normal load is a condition finding, not an efficiency finding. It points at bearings, alignment, voltage imbalance or an approaching failure. Treat those as reliability items that happen to cost energy, and schedule them against production rather than against payback.

Find out what your plant's invoice is actually paying for

Send twelve months of CFE invoices, your tariff class, a single line diagram and monthly production volumes. Mexico Energy Partners returns a tariff and load factor review, the measures worth metering, the scope and duration of the audit, and a fixed price for the work. You can request an audit scope and quote, or use the form below, which reaches the same team. We do not quote a saving before the measurement exists.

Sources

• Comisión Reguladora de Energía, memoria documental "Tarifas Finales del Suministro Básico", 31 October 2018, on Acuerdo A/058/2017 of 23 November 2017, which set the tariff methodology, and Acuerdo A/061/2017 of 29 November 2017, whose schedules applied from 1 December 2017.
• Acuerdo que autoriza el ajuste, modificación y reestructuración de las tarifas para suministro y venta de energía eléctrica, DOF 31 October 2000, on the power factor surcharge and bonus.
• Disposiciones administrativas que establecen los criterios para determinar cuándo un usuario cuenta con patrón de alto consumo de energía, DOF 15 November 2018.
• CONUEE, Usuarios de Patrón de Alto Consumo, program page and reporting window.
• CRE, RES/151/2016, Código de Red, DOF 8 April 2016.
• CRE, RES/550/2021, Código de Red, DOF 31 December 2021, in force 1 January 2022.
• SENER, Manual de Registro y Acreditación de Participantes del Mercado, DOF 15 July 2016.