CFE rate negotiation for data centers: how to avoid the cost trap

When you walk into CFE (Mexico’s federal electricity utility) to set up a data center with a contracted demand of 500 kW, the first thing they tell you isn’t how much you’ll pay. It’s that you sign a specific demand for 12 months, that if you lower it you’ll be penalized, and that every tariff change requires a study. That is the operational reality no brochure explains. What follows is what I learned reading the GDMTO and GDMTH rate schedules, talking with operators, and opening three CFE bills until I understood where the hidden overcharge lives.

Before talking about rates, one note: this article is not fiscal or legal tariff advice. CFE rates change every year (CRE publishes updates in the DOF, Mexico’s Official Gazette of the Federation). What follows applies to the tariff structure in effect in 2026 for medium voltage with demand greater than 100 kW. Before signing any contract with CFE, validate the numbers with your verification unit or with an electrical consultant registered with CRE.

The two rates that apply to you by size

For a data center with demand greater than 100 kW, the applicable rates fall under the High Demand (Gran Demanda) regime. There are two main modalities:

• GDMTO (High Demand Medium Voltage Ordinary). For users with demand equal to or greater than 100 kW, served at medium voltage (typically 13.8 kV or 34.5 kV in Mexico). Billing is based on maximum demand and on energy consumed, with three time-of-use periods (peak, mid-peak, base). The load factor used to calculate billable demand is 0.55.

• GDMTH (High Demand Medium Voltage Time-of-Use). Same as GDMTO but with 24 differentiated hourly periods instead of 3. This lets you optimize consumption if your data center has flexibility to shift loads to lower-cost hours. The load factor used is 0.60.

For data centers, GDMTH usually wins. But it requires measuring and recording hourly consumption with appropriate metering equipment (a multifunction meter with load profile). If your meter is old or doesn’t communicate with CFE, the switch to GDMTH requires installing new equipment. That investment pays for itself in 6-12 months if your consumption pattern is genuinely exploitable.

How your billable demand is calculated

Billable demand is what you actually pay each month, and it’s calculated with a formula that looks like a trap until you break it apart:

Billable demand = max(Maximum demand measured in the month, kW × LF × 24 × days of the month × hourly LF)

Where kW is your contracted demand and LF is the load factor (0.55 for GDMTO, 0.60 for GDMTH). In other words: if your actual consumption during the month was low (say 100 kW average), but your contracted demand is 500 kW, they still bill you at least the equivalent of 500 × 0.55 × 24 × 30 = 198,000 kWh-month, translated into kW of demand.

This means over-contracting demand is expensive. Very. A data center that contracts 500 kW and only consumes 200 kW is paying the rate for 500 kW with the 0.55 load factor. The difference, multiplied over 12 months, is hundreds of thousands of pesos that go straight into the air.

Power factor: the silent penalty

CFE charges you a surcharge if your monthly power factor falls below 0.90. The calculation is:

Surcharge = (0.90 / actual PF − 1) × Billable demand charge

If your power factor is 0.80, you pay a 12.5% surcharge on the demand charge. If it’s 0.70, it’s 28.5%. And so on. In a typical data center, with lots of electronic equipment (servers, switches, UPS) and precision AC units with variable frequency drives, the power factor without correction can drop to 0.75-0.85 without anyone noticing until the bill arrives.

The fix is to install an automatic capacitor bank, sized to correct the power factor to at least 0.95 (recommended, for headroom). The investment pays back in 4-8 months on the surcharge it saves alone. A 200 kVAR capacitor bank for a 500 kW data center costs between MXN $120,000 and $250,000 (approx. USD $6,860-$14,290 at 17.5 MXN/USD, verify Banxico FIX on publication day) installed.

Peak hours: when shifting loads is worth it

The peak window under the GDMTO/GDMTH rate is the most expensive period. In 2026, the typical peak windows are:

• Monday through Friday from 18:00 to 22:00 (CFE summer schedule).

• Monday through Friday from 18:00 to 22:00 (winter schedule).

The mid-peak window is 6:00 to 18:00 and 22:00 to 24:00 on business days. The base window is 0:00 to 6:00. Weekends and holidays are base rate all day.

For a data center, shifting loads to the base window is hard: IT load doesn’t stop (servers, switches, storage). What you can shift:

• Deferrable thermal loads. Water heating, pre-cooling the raised floor before the peak, scheduled load tests during base hours.

• Maintenance loads. Air filter cleaning (which requires opening dampers and exposing the room to outside air), generator tests, UPS maintenance that can be done on weekends.

• UPS battery charging. Some lithium batteries accept fast charging during base hours without affecting service life. Talk to the manufacturer before implementing this.

Why your contracted demand is a problem if it’s too high

The contract with CFE carries penalties for under-utilization. If you contracted 500 kW and your maximum measured consumption over 12 consecutive months was 250 kW, CFE adjusts your contracted demand to the measured value + 10%. That sounds fine until your real load climbs: if in month 13 you need 450 kW, they bill you the difference as uncontracted demand, at punitive rates.

The right strategy is to contract demand close to your actual operation, not your installed capacity. A data center with 1,000 kW of UPS capacity but operating at 60% should contract 600-700 kW, not 1,000. Growth capacity is covered with two tools:

1. Incremental demand contracts with CFE. You can request demand increases with 30 days’ notice. CFE approves it if the local grid has capacity. If it doesn’t, the wait can be 6-18 months.

1. Distributed generation (solar panels, natural gas, biogas). The Ley de la Industria Eléctrica (Electricity Industry Law) and the MEM (Wholesale Electricity Market) allow users with demand greater than 1 MW to participate in distributed generation as self-supply. For mid-size data centers (500 kW – 5 MW), this is increasingly common.

How to negotiate your demand when you show up at CFE

Three practical rules that apply in most states:

1. Study your load profile before the first meeting with CFE. You need a load study of at least 30 days (ideally 90) with demand profile every 15 minutes. With that, you can defend a specific contracted demand with data, not estimates. CFE respects data; estimates they challenge.

1. Ask for GDMTH from day one if your data center is above 500 kW. The cost of the meter and the communications is marginal compared to the potential savings. Even if you don’t optimize the schedule at first, having hourly metering gives you the data to optimize later.

1. Negotiate contracted demand with real growth headroom, not installed capacity. If your data center will operate at 70% in year one and at 90% in year three, contract year-one demand (say 350 kW), not year-three. Grow with incremental contracts.

What they never tell you about the energy charge

The energy charge has three components that aren’t always visible on the bill:

• Basic supply. The cost of energy as a commodity, the same for all users on the same rate and zone.

• Distribution charge. The network CFE uses to deliver your energy. Varies by region.

• Capacity charge. Recognizes the investment CFE makes in generation to have the power you demand available. This is charged even if you don’t consume energy.

The capacity charge is, in practice, a disguised fixed charge. For a data center with 500 kW of contracted demand, it represents between 15% and 25% of the total charge. That’s why the correct contracted-demand strategy matters so much: every kW you contract without using translates into a capacity charge you can’t recover.

Operational recommendations

1. Install a power analyzer on the main feeder of your data center. You need to see power factor, maximum demand, hourly profile, and harmonic content. Without that information, you’re negotiating with CFE blind. A Class A power analyzer (Schneider PM5560, ABB M4M 30, Eaton PXM6000) costs between MXN $25,000 and $80,000 (approx. USD $1,430-$4,570 at 17.5 MXN/USD, verify Banxico FIX on publication day).

1. Measure the power factor monthly. If it drops below 0.92, install or adjust the capacitor bank. Don’t wait for CFE to charge the surcharge.

1. Review your contracted demand every 12 months. If your operation changed (you closed a floor, opened another, switched cooling provider), your optimal demand changed.

1. Keep a record of the GDMTO/GDMTH rate behavior published in the DOF each year. Rates change quarterly for some components (fuel, inflation) and annually for others. What you signed in 2024 may not be the same as in 2026.

1. If you have a data center with demand greater than 1 MW, evaluate the option of participating in the Mercado Eléctrico Mayorista (Wholesale Electricity Market) as a Qualified User. It requires being constituted as a Generator or Supplier, but the rates are competitive against CFE for large consumers.

Sources

[1] Comisión Federal de Electricidad (CFE) — GDMTH Tariff — https://app.cfe.mx/Aplicaciones/CCFE/Tarifas/TarifasCRENegocio/Tarifas/GranDemandaMTH.aspx

[2] Comisión Reguladora de Energía (CRE) — Tariff Resolutions — https://www.cre.gob.mx/Resoluciones/

[3] Ley de la Industria Eléctrica — DOF 11-08-2014 — https://www.diputados.gob.mx/LeyesBiblio/pdf/LIE.pdf

[4] NOM-001-SEDE-2012 — Electrical Installations (utilization) — https://www.dof.gob.mx/nota_detalle.php?codigo=5280606&fecha=29/11/2012

[5] Diario Oficial de la Federación — Current GDMTO/GDMTH Tariffs — https://www.dof.gob.mx/