A Mexican site whose direct and indirect emissions total 25,000 tonnes of CO2 equivalent or more in a year has to report them to the Registro Nacional de Emisiones. The threshold is set by Article 6 of the Reglamento de la Ley General de Cambio Climático en Materia del Registro Nacional de Emisiones, published in the DOF on 28 October 2014. SEMARNAT operates that register under the Ley General de Cambio Climático, published in the Diario Oficial de la Federación on 6 June 2012. Above the threshold the emissions baseline stops being a management document and becomes a filing.

That changes what a net zero roadmap has to survive. The number must be reconstructible from records the site can produce on request, at a boundary someone outside the company can check. For electricity the boundary has a legal anchor. Article 3 of the Ley de la Industria Eléctrica, published in the DOF on 11 August 2014, defines a Centro de Carga as the installations and equipment that, at a given site, allow a final user to receive electricity supply. That is the unit the supply contract and the invoices attach to, so it is the unit an outside reviewer can reconcile the baseline against.

Mexico Energy Partners asks for two inputs before building a roadmap: twelve months of energy consumption data and a list of the energy-consuming equipment. Those two inputs set the boundary for everything that follows. What follows here is what they establish, what they cannot establish, and the sequencing rule that decides whether the capital plan works.

What twelve months of billing establishes

Twelve months of invoices on a medium-voltage supply give billed kilowatt hours split by tariff period, the billed maximum demand the site was charged on, and the measured power factor. They give the seasonal shape of consumption and the months in which demand, rather than consumption, drove the charge. They are also the only version of the site's usage a third party will accept without argument, because the supplier issued them.

The equipment list does the allocation. Rated kilowatts multiplied by operating hours, reconciled against billed kilowatt hours, produces a first-pass split of consumption across compressed air, refrigeration, process heat, pumping and lighting. The gap between the two totals is the useful output. It names the systems that are not yet accounted for, and those are where the first meters go.

Consumption and cost are separate questions from that point on. Kilowatt hours fall when a machine uses less energy. The demand charge falls only if the site's peak moves. A measure list that reports one number for both has not been priced. Our earlier note on what an energy audit actually establishes covers the measurement work that separates them.

What the two inputs cannot establish

Billing data and an equipment list do not produce a complete carbon inventory, and a roadmap that implies otherwise will not hold up in assurance. They say nothing about combustion at the site, so a gas-fired boiler, a fleet and any process emissions have to come from fuel purchase and maintenance records. They say nothing about refrigerant losses, which are reported as fugitive emissions and are traced through service logs rather than through meters.

They also say nothing about the load profile inside the month. An invoice reports the demand that was billed. It does not report the interval that set it. Two sites with the same billed demand can have entirely different peak structures, and a measure that flattens one will do nothing to the other. Any saving that depends on moving a peak needs interval data, and that is a second phase with its own metering and its own cost.

Stating this at the start is what makes the rest usable. A baseline with its boundary written down can be extended later. A baseline that quietly treats two inputs as a full inventory has to be rebuilt.

Where the emissions number becomes a regulatory artifact

Indirect emissions from purchased electricity are converted with the emission factor SEMARNAT publishes each year for the national electricity system. That factor is a national annual average. It does not describe the generation that physically served a site, and it does not move because a site signed a contract.

The clean attribute is a separate instrument. Article 3 of the Ley de la Industria Eléctrica defines a Certificado de Energía Limpia as a title issued by CRE certifying that a given amount of electricity was produced from clean sources. The certificate is issued to the generator and travels on its own. A site therefore has three distinct levers on its reported indirect emissions: consume fewer kilowatt hours, generate behind the meter, or acquire and retire the attribute. Only the first two also move the bill.

Why efficiency has to be priced before generation is sized

Onsite generation is sized against a load. Size it against a load measured before the efficiency program runs and the array is matched to consumption the site is about to stop having. What remains is generation the site cannot absorb in the hours it is produced, and surplus does not clear at the retail price.

The order that avoids this is measure, price the efficiency measures, re-forecast the load shape that survives them, then size generation against that shape. The choice between onsite versus offsite renewable options only becomes a real choice once the post-efficiency load is known, because the two options fail in different ways when the load forecast is wrong. An oversized rooftop array is a sunk cost. An oversized contracted volume is a recurring one.

What the Código de Red does to an efficiency program

An efficiency program changes the electrical character of a site, and in Mexico that has a regulator attached to it. The Código de Red was issued by the Comisión Reguladora de Energía as resolution RES/151/2016, published in the DOF on 8 April 2016. CRE reissued it as resolution RES/550/2021, published in the DOF on 31 December 2021 and in force since 1 January 2022. It applies to load centers connected at media tensión, above 1 kV and up to 35 kV, and at alta tensión, 35 kV and above, regardless of contracted demand and regardless of supply scheme.

At media tensión the requirements cover voltage variation, transient voltage, frequency variation, short circuit, protections, control systems, information exchange and current imbalance. At alta tensión they add power factor, current harmonic distortion and voltage flicker. Variable speed drives, electronic lighting drivers and new rectifier loads are the equipment an efficiency program installs, and they are also the equipment that raises current harmonic distortion. Capacitor banks fitted to correct power factor can resonate with those harmonics rather than solve them.

Studies have to use Class A measurement instruments under NMX-J-610/4-3-ANCE or IEC 61000-4-30. Load centers connected before 8 April 2016 had until 9 April 2019 to comply. CRE holds compliance and sanction authority, while CENACE operates the system and the market. CRE does not authorize or certify the firms that carry out these studies. A load center may perform them itself or contract a specialist. A supplier insisting that only an approved verifier can sign them is describing a requirement the resolution does not contain.

The practical consequence for the roadmap is one line in the capital plan. A drive retrofit at an alta tensión site should carry a power quality measurement before and after, on Class A instruments, in the same budget as the drives.

What a power purchase agreement fixes and what it leaves open

A power purchase agreement fixes the price of the contracted energy volume for the term of the contract. It does not fix transmission and porteo, capacity or ancillary services charges, and it does not cover whatever residual supply the site continues to take. A roadmap that presents a contract as protection against price movement should state which components of delivered cost it covers and which stay floating.

The emissions treatment is a separate question again. Whether the contract reduces reported indirect emissions depends on whether the clean attribute is transferred and retired on the buyer's account, which is a term of the contract rather than a property of the plant supplying it. Our note on corporate PPAs in Mexico sets out the structures in use.

Request a net zero roadmap for your Mexican site

Send twelve months of electricity invoices showing billed kilowatt hours by period, billed maximum demand and power factor, together with an equipment list giving rated kilowatts and operating hours. Mexico Energy Partners returns an emissions baseline with its boundary written down, a ranked measure list with indicative capital cost and the split between energy and demand effects, and a sequence that prices efficiency before any generation is sized. Where the two inputs are not sufficient, the response says which second-phase data is needed and why. There is no charge for the roadmap. Nothing about savings or eligibility is settled before the data has been read.

Sources

• Diario Oficial de la Federación, Ley General de Cambio Climático, 6 June 2012, for the Registro Nacional de Emisiones.
• Diario Oficial de la Federación, Reglamento de la Ley General de Cambio Climático en Materia del Registro Nacional de Emisiones, 28 October 2014, Article 6, for the 25,000 tCO2e reporting threshold.
• Diario Oficial de la Federación, Ley de la Industria Eléctrica, 11 August 2014, Article 3, for the definitions of Centro de Carga and Certificado de Energía Limpia.
• Comisión Reguladora de Energía, resolution RES/151/2016, Código de Red, published in the DOF on 8 April 2016, for the voltage bands, the parameter requirements, the Class A instrument requirement and the 9 April 2019 compliance date.
• Comisión Reguladora de Energía, resolution RES/550/2021, Código de Red, published in the DOF on 31 December 2021, which reissued RES/151/2016 and took effect on 1 January 2022.
• Comisión Reguladora de Energía, Guía sobre los requerimientos técnicos del Código de Red aplicables a Centros de Carga, for the scope and the position that CRE does not certify the firms performing the studies.