Read this before you switch anything off
A facility that shuts down or drops to a skeleton crew can take real cost out of its electricity bill within days. It can also injure people and destroy equipment on the way back up. Ventilation, cooling and process systems that were deactivated for a shutdown have to be restarted in a controlled sequence, and a plant that restarts them all at once puts staff into a space that has not been ventilated and puts a surge onto a meter that is still recording. Name one person as the owner of the shutdown record before anything is de-energized, and make the restart sequence part of the same document as the shutdown sequence.
That is the safety case. The commercial case is narrower than most operators assume. A shutdown cuts consumption immediately. It does not cut the demand charge, and an unmanaged restart can raise it.
What a shutdown does to each line of the CFE bill
An industrial or large commercial site in Mexico is billed under a CRE-approved tariff class. Sites on medium-tension supply with demand of 100 kW or more sit on GDMTH, the time-of-use class with base, intermedio and punta periods. Larger loads taken at subtransmission or transmission voltage sit on DIST or DIT. Every one of those classes bills two things separately.
The energy charge bills kWh. It falls the day the load comes off, roughly in proportion, and this is the part of the saving a shutdown delivers automatically.
The demand charge bills kW at the peak the meter records during the billing period, weighted toward the punta window. It does not fall because the site was mostly empty. It falls only if the highest peak in the period came down. A plant that idles for three weeks and then brings chillers, compressors, ovens and lighting back on inside the same fifteen minutes can set a new period peak that costs more than the three quiet weeks saved. Stagger the restart across the base period and the demand charge follows the shutdown rather than fighting it.
This is the single decision worth taking out of this article into an operations meeting. Ask which line each proposed change touches, and treat consumption reduction and demand reduction as separate objectives with separate methods.
Building the asset list
Start with an inventory of what can safely be turned down, turned off, or left alone, and mark each item with who has authority to change it and how it is changed.
- HVAC: chillers, air handlers, rooftop units, exhaust fans, and any dedicated process cooling.
- Building automation: what the BMS can reconfigure remotely and what requires someone on site with a key.
- Industry-specific equipment that normally runs continuously, including generators, cooling towers and compressed air, where a long stop is possible but a cold start is not trivial.
- Standby loads. Vending, display, signage, office equipment and idle production controls draw power while apparently off, and for many of them the only reliable stop is at the outlet or the breaker.
- Lighting. Interior lighting in non-residential buildings is covered by NOM-007-ENER-2014, published in the Diario Oficial de la Federación on 7 August 2014 and in force from 5 December 2014, with CONUEE as the responsible authority. A shutdown is the practical window for a lighting change, since the work does not interrupt production.
Setpoints, in degrees Celsius
Mexican building systems are set in Celsius and the figures below are Celsius. That distinction matters, because a setback of 3 written for a Fahrenheit thermostat becomes a setback nearly twice as large when the same number is entered on a Celsius thermostat, and a change that reads as conservative in one unit is aggressive in the other.
For a shutdown measured in weeks rather than nights, the usual night or weekend setback is too narrow. Widen the unoccupied band and let the binding constraint be an actual limit rather than a rule of thumb. Two limits usually bind first. One is the moisture limit below. The other is whatever spec governs stored product, finished goods, calibration rooms or wood and paper stock in the building. Raise the cooling setpoint until one of those two limits is reached, then stop.
Refrigerators, freezers and display cases that hold nothing can be emptied and shut off entirely, which removes both their own load and the heat they reject into the space.
Humidity, and why Yucatán is a different problem from Sonora
The regional split is real and it changes the answer. In Sonora and much of the north, raising the cooling setpoint during a shutdown is close to free money. In cooler parts of Baja California, pushing the setpoint too high can call the heating system on and raise the bill instead of lowering it, so check that the deadband between heating and cooling setpoints is wide enough before you touch either.
On the Yucatán Peninsula and the coasts the constraint is moisture, not temperature. ASHRAE's guidance for building operations during the pandemic, published in ASHRAE Journal on 24 March 2020, points to ASHRAE Standard 62.1-2019, which requires a maximum dew point of 60 °F, or 15.6 °C, during both occupied and unoccupied hours where the outdoor air dew point is above that figure. Dew point is the better control target than relative humidity for an empty building, because relative humidity moves with temperature and a space that is drifting warm can read acceptable while the actual moisture load is climbing. A cooling system switched off in a humid coastal plant will not hold that limit, which is why the correct move in Mérida or Veracruz is usually to keep dehumidification running at reduced capacity rather than to shut the system down.
Recording it, and why CONUEE cares
Every change gets logged: the asset, the previous setting, the new setting, the date, who made it, and the sequence position for the restart. One named owner holds the record. That log is what allows a controlled restart, and it is also the raw material for a savings claim that survives review, since the alternative is comparing two bills and calling the difference a result.
There is a regulatory reason too. Sites that cross the thresholds in the administrative provisions published in the DOF on 15 November 2018, an annual electricity consumption above 45 GWh or fuel consumption above 100,000 barrels of crude oil equivalent, report to CONUEE each year on their consumption and on the energy conservation measures they implemented and what those measures produced. A shutdown log written properly is most of that filing.
What sits outside this article
Everything above is what a facility team can do with the assets it already has. The financing routes, the FIDE and development bank programs, and the tariff and contract questions behind them are covered separately in the guide to Mexico's energy efficiency programs and financing. For how the CONUEE reporting regime and the wider Mexican efficiency framework fit together, see the overview of the market for industrial and commercial buyers.
Review a shutdown and restart plan for your site
Mexico Energy Partners reviews shutdown and restart sequences against a site's tariff class and demand profile, so that the restart does not set a new billing peak and the systems that protect people and equipment come back in the right order. An initial review needs 12 months of CFE billing, the tariff class, a load list, the single-line diagram, and the BMS points list where one exists.
See how our energy efficiency assessments work or schedule a technical call on a shutdown plan.