Across 165 photovoltaic systems with clean operating data, kWh Analytics measured mean availability of 96.4% to 97.2%, against the 99% that project models routinely assume. That analysis was published on 1 July 2024 and covers United States assets, so it is a warning rather than a Mexican statistic. The warning travels, because in most onsite solar leases and power purchase agreements the party that reports the generation is also the party that issues the invoice.
Mexico Energy Partners is launching PPA & Solar Watch, a subscription service that reconciles metered output against supplier invoices and against the yield study the project was sold on. The decision it supports is narrow. You either accept the kWh figure your generator reports and pay it, or you verify that figure before you pay.
What follows sets out what independent verification consists of, what it can recover, and what it cannot. It is written for owners who already signed, whether the asset sits on their roof or supplies them under a PPA structured for the Mexican market.
How much of this asset base now exists in Mexico
The Comisión Reguladora de Energía closed 2024 with 4,447.92 MW of distributed generation interconnected, across 518,019 interconnection contracts. That is 35.3% more capacity than the 3,361.69 MW recorded at the end of 2023, and 99.409% of it is solar photovoltaic. pv magazine reported those figures on 4 February 2025.
The regulatory ceiling on that segment moved in 2025. Under the Ley del Sector Eléctrico, a plant below 0.7 MW needs no generation permit. The Comisión Nacional de Energía published its acuerdo setting the permit requirements for interconnected self-consumption plants between 0.7 MW and 20 MW in the Diario Oficial de la Federación on 6 August 2025, as Greenberg Traurig summarized on 12 August 2025. Applicants must file technology and capacity in AC and DC, estimated annual output, georeferenced coordinates, a single line diagram, two years of financial statements and a business plan.
Two consequences follow for owners. Systems are getting larger, so the value of a percentage point of underperformance is rising. And the estimated annual output filed with the regulator becomes a written number the asset can be measured against later.
Where owners lose money after commissioning
The generation shortfall is the first leak. In its 2022 Solar Generation Index, published 8 December 2022, kWh Analytics found 2021 operational data showing close to 8% average underproduction on a weather-adjusted basis. Projects built after 2015 missed their P50 estimates by 7% to 13% in the first year of operation. Both figures are United States portfolio findings. Neither has a published Mexican equivalent that we can point to.
The second leak is invoicing. Where the generator meters, reports and bills, the owner has no second reading to check against. A month of inverter downtime that never reaches the monthly report is a month of energy billed and not delivered. The correction is not complicated. It is a meter reading the owner controls, reconciled line by line against the invoice.
The third leak is silence in the contract. Availability guarantees and performance guarantees are only worth the notice periods attached to them. A shortfall identified fourteen months late is usually a shortfall the owner absorbs.
What PPA & Solar Watch checks each month
The service has four components, and each one produces a document rather than a dashboard impression.
Generation and performance. We review energy produced in kWh against the expected curve from the project's own yield study, together with system availability and the events recorded by the inverters. The expected curve is the P50 estimate in the project documents, not a figure we invent, and the deviation band that triggers an alert is agreed with you in writing at the start. That is the difference between continuous energy monitoring and a monthly PDF from the supplier.
Supplier billing. We cross-check generation data against the invoices issued by the generator or solar provider, verify that billed volumes match energy actually delivered, and flag overcharges and inconsistencies with the underlying interval data attached, so the clarification you file has evidence in it.
Alerts and operational recommendations. When output falls outside the agreed band we issue an alert with a cause, not a color. Typical causes are soiling, string or combiner faults, inverter derating in high ambient temperature, and shading from equipment installed after commissioning. The recommendation names the action, for example a cleaning cycle, a targeted inspection, or a configuration review.
Quarterly executive report. Management and finance receive cumulative performance for the PPA or solar project, the saving achieved against the CFE tariff, and the open risks. The report states which tariff class and which billing month the comparison uses.
Why the CFE comparison has to name the tariff
A saving against the CFE tariff is not one number. A GDMTH bill separates supply, transmission, distribution, CENACE services, energy by hourly period, capacity, and system operation services, as Marsam Solar set out on 1 March 2022. The capacity charge is calculated on maximum demand recorded in the punta period.
That matters for how you read a solar saving. Generation displaces kWh, which reaches the energy charge directly. The capacity charge follows the demand peak, and for a plant that runs past sunset the punta peak often sits outside solar hours. A quarterly report that presents one blended percentage without saying which charges moved is not a report a finance director can defend.
So the comparison in our report names the tariff class, the billing month used as the basis, and which charge lines changed. Where an owner also holds a supply contract as a qualified user, the same discipline applies to the supplier's energy price rather than to the CFE schedule.
What independent supervision cannot do
Monitoring does not deliver energy. It detects a shortfall, evidences it, and tells you whether your contract converts that evidence into a credit. If the agreement has no availability guarantee, or the notice period has passed, the finding is useful for the next contract and for nothing else. We say so in the report rather than around it.
Monitoring also does not change the contract price. If the PPA price sits above the tariff you would otherwise pay, verification will confirm that accurately and repeatedly. The remedy there is renegotiation or replacement at term, not supervision.
What makes the opinion independent is structural. Mexico Energy Partners does not sell the equipment, does not hold the operations and maintenance contract, and is not paid on generation. That is worth more than an adjective, and it is the reason the reconciliation can conclude against the supplier who installed the system. Owners weighing a second asset can read our view of onsite solar economics in Mexico alongside the verification service.
Have your generation data and supplier invoices checked
We reconcile metered kWh against the generator's invoices for the last twelve months and report the variance, the cause we can evidence, and whether the contract supports a claim. We do not estimate a recovery before that reconciliation is done.
To start, send the PPA or lease, twelve months of supplier invoices, an export from the inverter or monitoring portal, and one CFE bill for each affected meter. We confirm the scope and the data gaps before any work begins. Use the form below to request a performance review.
Sources
- kWh Analytics, "Bringing solar availability assumptions back down to earth: the case for adjusting to 97%", 1 July 2024. Mean availability of 96.4% to 97.2% across 165 systems drawn from a database of 485 commercial, industrial and utility-scale systems.
- kWh Analytics, 2022 Solar Generation Index, reported by Solar Builder on 8 December 2022. Close to 8% weather-adjusted underproduction in 2021 data, and post-2015 projects missing P50 by 7% to 13% in year one.
- Comisión Reguladora de Energía distributed generation statistics for 2024, reported by pv magazine on 4 February 2025. 4,447.92 MW interconnected across 518,019 contracts, 35.3% growth on 2023, 99.409% solar photovoltaic.
- Comisión Nacional de Energía, acuerdo on permit requirements for interconnected self-consumption plants of 0.7 MW to 20 MW, Diario Oficial de la Federación, 6 August 2025, summarized by Greenberg Traurig on 12 August 2025.
- Marsam Solar, "Tarifa GDMTH: qué es, cómo se cobra y cómo influye en tu empresa", 1 March 2022. Billing components of the GDMTH tariff and calculation of the capacity charge on maximum demand in the punta period.