Mexico closed 2022 with 2,629.78 MW of distributed generation across 334,984 interconnection contracts, of which photovoltaic systems accounted for 2,611.37 MW. pv magazine México published the CRE breakdown on 14 April 2023. Almost every one of those systems sits below one number, 0.5 MW, and that number is the one most rooftop solar material in Mexico gets wrong.
Article 17 of the Ley de la Industria Eléctrica, published in the Diario Oficial de la Federación on 11 August 2014, exempts a generating plant below 0.5 MW from holding a CRE generation permit. It exempts nothing else. A rooftop array still needs an interconnection contract with CFE Distribución, a bidirectional meter, an electrical installation certified against NOM-001-SEDE-2012, and municipal construction and land use approval.
What does the 0.5 MW threshold actually exempt?
One instrument. Below 0.5 MW you do not apply to CRE for a permiso de generación. Every other step still applies.
SENER set that process out in the Manual de Interconexión de Centrales de Generación con Capacidad menor a 0.5 MW, published in the DOF on 15 December 2016. It sorts systems into baja tensión, below 50 kW three phase or 30 kW single phase, media tensión tipo 1 to 250 kW, and media tensión tipo 2 from 250 kW to under 500 kW. Where the circuit requires a study, the manual gives CFE Distribución ten business days to issue the works budget, and ten business days to sign the Contrato de Interconexión once technical requirements are settled. A bidirectional meter is mandatory in every case.
Check one unit trap before assuming you are inside the threshold. The exemption is written in MW of generating capacity. A quotation written in kWp gives the peak DC rating of the modules, which is a different quantity from the capacity the interconnection application declares. Ask the developer which figure goes on the application, because the distributed generation rules in Mexico follow from that number.
Do I need permits to install rooftop solar in Mexico?
Yes. The claim that no permits are required below 500 kWp is false, and it is false in a way that costs schedule rather than money.
Four approvals apply to a normal industrial rooftop project. The interconnection contract with CFE Distribución is the federal one, under the 2016 manual. The electrical installation has to comply with NOM-001-SEDE-2012, published in the DOF on 29 November 2012, evidenced by a dictamen from an accredited unidad de verificación under the conformity assessment procedure of 18 June 2014. The licencia de construcción and the uso de suelo confirmation are municipal, and requirements differ between municipalities, so no national statement covers them. Structural sign off is the fourth, and in most states it runs through a director responsable de obra.
None of this is hard. All of it consumes calendar. A project plan built on the assumption that nothing needs approval will miss its energization date.
What happens to the electricity I export?
Not sold back to the grid at your tariff. CRE's distributed generation rules, issued as RES/142/2017 and published in the DOF on 7 March 2017, offer three schemes.
Medición neta, the one most Mexican customers sign, credits exported energy against later consumption rather than paying cash for it. Credit still unused after twelve months is liquidated at the local marginal price of the node, well below the retail tariff. Facturación neta bills injections and consumption as separate transactions and pays the injected energy at the local marginal price. Venta total sells the entire output at that price and self consumes nothing.
The practical consequence is that oversizing an array past your own daytime consumption converts kilowatt hours worth the retail tariff into kilowatt hours worth the wholesale price. Size to the load, not to the roof area.
How much of a CFE invoice can a rooftop array reach?
Less than the headline percentages suggest, and the reason sits in the tariff rather than in the panels. CRE set the methodology behind the basic supply tariffs in Acuerdo A/058/2017, dated 23 November 2017. A gran demanda en media tensión horaria invoice carries a fixed charge, capacity and distribution charges billed on measured demand in kW, and energy charges split across base, intermedia and punta hours.
Two of those charges are levied on kilowatts, not kilowatt hours. An array displaces energy while the sun is on it, so it moves the energy charges. Whether it also lowers the measured demand behind the capacity and distribution charges depends on when the plant peaks. On Mexican industrial sites that peak often falls outside the generating window, or on a cloudy interval inside it, and the demand driven charges then barely move. Check your region's horario and your own interval data first.
Size the array yourself before anyone quotes you. Take twelve months of invoices, separate the peso total of the energy charges from the demand and fixed charges, then apply an annual yield. The World Bank and ESMAP's Global Photovoltaic Power Potential by Country, published in June 2020, places Mexico among the countries whose long term daily output averages exceed 4.5 kWh per kWp. At that level, and this is our arithmetic on the World Bank figure rather than a measured result, a 500 kWp array yields on the order of 820 MWh a year. That World Bank figure already carries the report's assumed 3.5% soiling loss and 7.5% of inverter, cabling, mismatch and inter-row shading losses. Set that against your metered daylight consumption. The ratio is the ceiling on what an array can offset, and it is the number to argue about. For the wider case, see the case for rooftop solar in Mexico.
Are there upfront costs?
That depends entirely on the contract, and an answer that does not name the contract is not an answer.
Buy the system and it is capex on your balance sheet. Against that, Article 34, fracción XIII of the Ley del Impuesto Sobre la Renta allows equipment for generation from renewable sources to be deducted at 100% in the year of the investment. The condition is that the assets stay in operation for at least five consecutive years afterwards. Fail that test and the difference between the 100% deduction and the ordinary rate becomes payable.
Take a lease or an onsite power purchase agreement instead and a third party owns the system, carries the capex and bills you per kilowatt hour delivered. No upfront cost is a feature of that structure, not a property of rooftop solar. The same goes for upkeep. Operation and maintenance sits inside the energy price only where an O&M agreement or a PPA puts it there.
How long does a project take?
The regulated steps are short. The rest is not. Nothing in the interconnection manual sets the calendar for the structural survey, module and inverter procurement, municipal licensing, the verification unit dictamen or the meter change, and those govern the energization date. No public dataset gives an average duration for a commercial rooftop project in Mexico, and Mexico Energy Partners has not published a schedule sample. Treat any single figure you are handed as the quoting party's own estimate and ask for the critical path behind it.
How long do the modules last, and how much output is lost each year?
Design life and warranty are different things, and neither is a degradation rate. Model the measured number. Dirk Jordan, Sarah Kurtz, Kaitlyn VanSant and Jeff Newmiller published the Compendium of Photovoltaic Degradation Rates in Progress in Photovoltaics in 2016, drawn from more than 11,000 measurements. It puts median degradation for crystalline silicon at 0.5 to 0.6% a year, with a mean of 0.8 to 0.9%. It also finds that hotter climates and mountings that hold module temperature high raise the rate in some products.
Run the arithmetic both ways. At 0.6% a year, output in year 25 is about 86% of year one. At 0.9% it is about 80%. On a hot Mexican roof the higher figure is the prudent one. Ask the supplier for the module datasheet, both warranty terms and the warranted annual degradation, then model against the warranty.
What happens on cloudy days and at night?
Output falls with irradiance and stops at sunset. The grid covers the rest, which is why the interconnection contract and the demand charges stay on the invoice whatever the array does. Battery storage changes that answer and brings its own capex, so it belongs in a business case of its own. The note on onsite solar economics covers the load profile question.
Will the roof carry the array?
Sometimes, and the assessment is not a formality. What matters is the remaining service life of the roof against the working life of the array, purlin spacing and permissible load, wind uplift on the mounting system, and whether the design uses ballast or penetrations. If the covering will need replacing before the array does, the cost of removing and reinstalling belongs in the model from the start. Ask who signs the verdict. It should carry the name of a licensed structural engineer.
Find out what array your roof and your interconnection will carry
Mexico Energy Partners reviews the invoice and the roof together. The output states which CFE charge lines an array can reach on your site, the capacity the roof and the circuit will support, the approvals to clear, and the contract structures available. You supply twelve months of CFE invoices, your tariff class and contracted demand, the roof area, age and construction, and the site address.
Use the form below to request a rooftop solar feasibility review, or reach the team through the Mexico Energy Partners quote request page. No saving or eligibility is promised before the invoices and the roof have been seen.
Sources
- Ley de la Industria Eléctrica, Diario Oficial de la Federación, 11 August 2014. Article 17, generation permit exemption below 0.5 MW.
- Secretaría de Energía, Manual de Interconexión de Centrales de Generación con Capacidad menor a 0.5 MW, DOF, 15 December 2016. Classes, deadlines, meter and Contrato de Interconexión.
- Comisión Reguladora de Energía, RES/142/2017 on generación distribuida, DOF, 7 March 2017. Medición neta, facturación neta and venta total.
- Comisión Reguladora de Energía, Acuerdo A/058/2017 of 23 November 2017. Methodology for the final basic supply tariffs.
- NOM-001-SEDE-2012, Instalaciones eléctricas, DOF, 29 November 2012, and its Procedimiento para la Evaluación de la Conformidad, DOF, 18 June 2014.
- Ley del Impuesto Sobre la Renta, Article 34, fracción XIII. Deduction at 100% for renewable generation equipment, conditioned on five consecutive years of operation.
- pv magazine México, La generación distribuida al cierre del 2022 en México, 14 April 2023, reporting CRE statistics for year end 2022.
- World Bank and ESMAP, Global Photovoltaic Power Potential by Country, June 2020. Daily output above 4.5 kWh per kWp.
- Dirk Jordan, Sarah Kurtz, Kaitlyn VanSant and Jeff Newmiller, Compendium of Photovoltaic Degradation Rates, Progress in Photovoltaics, 2016. Degradation rates for crystalline silicon.