The annex that decides fifteen years
A technical requirement changed the economics of every new renewable generation project in Mexico through 2030. It does not live in a law or in a regulation: it lives in the annex of an administrative call for applications that has already revised its own calendar three times. The public debate is whether the requirement is right. For anyone financing a project, the question that matters is a different one: how hard is it to change.
On 11 May 2026, Mexico's Ministry of Energy published in the Federal Official Gazette the Second Call for priority processing of generation permit and grid interconnection applications, aligned with what the instrument itself calls Binding Planning. It is addressed to projects of 0.7 MW or more, with commercial operation between 2027 and the first half of 2030.
Its Annex 14.4 establishes that the electrical energy storage system must be sized at no less than 30% of the power plant's capacity, with a minimum duration of three hours.
Alongside that requirement sits a second fact that on its own would look merely administrative: the call has revised its calendar three times in four months. The application window before the National Energy Commission ended up running from 6 July to 6 August 2026, and the resolution was moved to an extraordinary session of the Technical Committee on 8 and 9 October, with notification on the 13th.
Together the two facts say something neither says alone. According to sector specialists' estimates, an imported battery system raises a project's total CAPEX by 25% to 35%, with an effect of 10% to 25% on the levelised cost of energy. A requirement of that magnitude, governing investment decisions through 2030, is not in the Electricity Sector Act, nor in its regulations, nor in the regulator's general provisions. It is in the annex of an instrument that has already proven three times that it can be modified.
On one side, a real and well-diagnosed need. Mexico's grid has no room to absorb more intermittency, firmness costs money, and someone has to pay for it. Requiring storage is a technically defensible answer to the same problem the system has failed to solve for years through transmission: as of late August 2026, the Federal Electricity Commission was still reporting 77 transmission projects pending tender worth 95,063 million pesos, with the same figures as in April.
On the other side, the legal rank of the chosen instrument. An administrative call can be revised call by call, with no legislative process and no public consultation. The instrument is named Binding Planning; its calendar has not been binding.
The tension is not between regulating and not regulating. It is between the content of the rule and the rank of the instrument that holds it. Regulatory certainty does not come from what the rule says; it comes from how hard it is to change. A structural requirement housed in a revisable annex communicates precisely the opposite of what its content is meant to secure.
There is a second pole worth naming without adjectives: the requirement shifts to the private generator, through batteries, part of the firmness cost the public grid does not provide. As long as the grid does not grow, whoever wants to connect buys the backup.
If the requirement that defines your project's returns can change between one call and the next, are you financing an asset or are you financing a position in a rule?
It lands first on the mid-sized Mexican developer of distributed generation and intermediate-scale parks: the one competing in the 0.7 to 30 MW range, without the balance sheet to absorb an extra 30% of CAPEX or the legal structure to hedge regulatory risk across a fifteen-year debt contract. An international player with cheap capital and the ability to import batteries at scale absorbs the requirement as one more cost. A local developer absorbs it as a change of business.
It also lands on the Mexican industrial user who had a renewable self-supply project in the pipeline as a hedge against the electricity tariff, and who is about to discover that the number presented a year ago is no longer the number.
And it lands, less visibly, on domestic suppliers. There is no Mexican storage-system supply chain: the requirement is met by importing. Every additional point of stringency is demand that leaves the country.
The effect that matters is not the cost increase, it is the compositional one. If the requirement holds, Mexico's renewable generation market does not stall: it concentrates. The local developer does not disappear because of adverse regulation — the rule is the same for everyone — but because of the cost of entry. Mexico may end this decade with more installed storage and fewer national developers building it, which is one way of strengthening a system by weakening whoever builds it.
The window has a date. The Technical Committee of the National Energy Commission resolves the Second Call on 8 and 9 October 2026 and notifies on the 13th. And on 7 October the 180-calendar-day deadline expires for issuing the Regulations of the Strategic Infrastructure Investment Act and the Finance Ministry's guidelines. Both dates fall in the same week, and that week is the best observation point of the year for knowing whether the requirement will rise in legal rank or stay where it is.
If you have a project in the pipeline or a self-supply decision on the table, the decision available in the next forty days — and which gets more expensive if you wait for the outcome — is to stop treating the requirement as a project input and start treating it as a variable with its own scenario.
First move, this week: ask whoever structures your base case to rerun it with three values of the storage requirement — the current 30%, a 40% scenario, and a no-requirement scenario — and to tell you in which of the three your project stops working. That is the number you need, not the base case. If your project only works in one scenario, you do not have a project: you have a bet that the annex will not change a fourth time.
Second move, for the week of 5 October: watch whether the requirement is incorporated into the National Energy Commission's general provisions or into the Regulations of the Electricity Sector Act. If it rises in rank, the uncertainty currently penalising your cost of capital drops and it makes sense to accelerate. If it is still in the annex when the third call is issued, the signal is that in this market the rule is a variable, and that changes what kind of project makes sense to finance in Mexico through 2030.
The signal that doesn't fit the reading. It's published anyway: a note that only shows what confirms it isn't a reading, it's an argument.
- Second Call for priority processing of electricity generation permit and SEN interconnection applications, aligned with Binding PlanningSecretaría de Energía · Diario Oficial de la Federación · May 11, 2026
- Second Call for electricity generation permits: a new window of opportunity for project developers in MexicoSantamarina y Steta · May 13, 2026
- Mexico: SENER prioritises new electricity generation permits and sets a binding calendarGarrigues · May 14, 2026
- New solar and wind projects in Mexico will get more expensive under the storage rule: expertDossier Político · Aug 7, 2026
Verified on 27 August 2026. The wording of the requirement is checked against the verbatim quotation reproduced by Garrigues: "that the sizing of the electrical energy storage system be at least 30% of the power plant's capacity". Four independent law firms — Santamarina y Steta, Garrigues, Mijares and Mondaq — agree on the percentage, on the three-hour minimum duration, on the requirement's location in Annex 14.4, on the 11 May 2026 publication date in the Official Gazette, on the 0.7 MW threshold and on the three calendar amendments.
What could not be done, and is declared here: the full text of the call in the Official Gazette was not read directly. The PDF of one of the amendments is no longer available on its origin server. The note rests on the agreement of four specialist sources and on a verbatim quotation, not on a reading of the original document.
On the basis for calculating the 30%, the note deliberately does not assert it: the document, according to the sources consulted, says "capacity of the power plant" without specifying whether this is measured against installed, net or gross capacity. That a requirement of this economic weight does not fix its own basis of measurement is itself part of what the note describes.
The figures of 25% to 35% CAPEX increase and 10% to 25% on levelised cost of energy are sector specialists' estimates, not official figures, and come from a source with an interest in seeing the requirement relaxed. They are cited as such and are not used for any derived calculation. The CFE transmission figures — 77 projects pending tender, 95,063 million pesos — are those reported in April 2026; no later report has been located.
What would weaken this reading, written before it appears.
First, the most boring explanation: that a call published in the Official Gazette is as binding as any rule for whoever takes part in it, and that the instrument's rank is irrelevant in practice. That is true for a participant in this call. It stops being true for anyone planning to 2030 who needs to know what the third call will require. The note is about predictability between calls, not enforceability within one.
Second, who wins if this is believed. Private developers who want the requirement relaxed, and their legal advisers: both the reading of the instrument and the cost-overrun estimates come from law firms. Naming this does not invalidate the fact — the percentage, the duration, the annex and the three amendments do not depend on them — but it conditions the interpretation and forces us not to exceed what the sources support.
Third, and this weighs most: the signal archive contains a case running in the opposite direction. In Mexico City, a mechanism born in July 2025 as a revocable administrative agreement to speed up housing permits became, within twelve months, a draft reform of three separate laws. It is proof that in Mexico an administrative instrument can indeed rise in legal rank when there is will to consolidate it. If that happens with the storage requirement before the third call, this note will be describing a transitional stage rather than a pattern, and that will need to be said.
Written before the counter-evidence appears.