Backup Power and Flexible Load Metering for AI Data Centers: What Changes at the POI During Grid Emergencies

Introduction: Why Backup Power Is Becoming a Grid Issue

In 2026, PJM developed additional procedures for coordinating backup resources at data centers and other large loads during severe system emergencies.

Revision 98 materials for PJM Manual 13 include Attachment O, which describes how PJM, Transmission Owners, Electric Distribution Companies and other relevant parties may coordinate with large-load customers when a federal emergency order under Section 202(c) of the Federal Power Act is in effect. PJM also referenced Revision 98 Attachment O in its 29 June 2026 emergency posting.

Attachment O is not a permanent, independent dispatch authority. It describes additional actions intended to avoid or reduce firm load interruption when the necessary federal emergency authorisation is in effect.

On 27 June 2026, PJM requested temporary authority to direct backup resources at large loads—including auxiliary, standby, directly connected, battery-storage and other resources—to operate as a last resort before declaring an Energy Emergency Alert Level 3, or during an EEA 3.

On 30 June 2026, the U.S. Department of Energy issued a temporary emergency order authorising PJM, in coordination with Transmission Owners and Electric Distribution Companies, to direct such backup resources to operate under those conditions. The order was scheduled to remain effective from 11:59 p.m. EDT on 30 June through 11:59 p.m. EDT on 3 July 2026.

This was a time-limited emergency authorisation rather than a permanent general dispatch right.

Separately, PJM has identified onsite generation, battery discharge and flexible computing workloads as potential tools for managing the integration challenges created by rapidly growing data-center demand.

This creates an important measurement question:

When grid import falls during an emergency, how can operators determine whether the change came from actual facility-load reduction, battery discharge or onsite generation?

A lower reading at the point of interconnection (POI) does not automatically mean that the data center reduced its underlying electrical demand. Reliable attribution requires separate, time-aligned measurements for the grid connection, generators, battery systems, Uninterruptible Power Supply (UPS) paths and major load categories.

1. Normal, Restricted and Emergency Operating Modes

The following modes are project-level analytical categories. They should not be treated as substitutes for PJM, utility or site-specific emergency classifications.

Normal Operation

During normal operation:

• The grid supplies most or all facility demand.
• UPS systems and batteries follow their normal reliability strategy.
• Backup generators remain off or operate only for testing.
• IT and cooling loads follow standard operating schedules.
• A site-level BESS may perform peak management or other scheduled functions.

Project-Defined Restricted or Flexible Operation

During a project-defined restricted or flexible period:

• Grid-import capacity may be limited.
• Selected computing workloads may be delayed or shifted.
• Non-critical cooling or auxiliary equipment may be adjusted.
• A BESS may discharge to limit POI demand.
• Battery charging may be delayed.
• Import or export limits may be applied by the site controller.

Emergency Operation

During an emergency:

• Backup generators may start.
• UPS batteries or a site-level BESS may support critical loads.
• Interruptible loads may be disconnected.
• Grid import may fall sharply.
• The facility may operate in parallel with the grid, transfer between sources or enter an islanded state.

Each operating period should be identified in the Energy Management System (EMS), Data Center Infrastructure Management (DCIM) platform or event record. Normal, restricted, transfer, emergency, islanded and recovery periods should not be combined into one undifferentiated dataset.

2. Why POI Data Alone Cannot Explain the Response

The POI meter records the net electrical exchange between the facility and the grid.

A simplified power-balance relationship during grid-connected operation may be written as:

Grid import
+ onsite generation
+ BESS discharge
=
facility electrical demand
+ BESS charging
+ defined site electrical losses
+ grid export

All values must be time-aligned, use consistent sign conventions and refer to compatible electrical boundaries.

The definition of facility electrical demand should state whether it includes:

• IT load
• Cooling and mechanical load
• UPS conversion losses
• Distribution losses
• Generator or BESS auxiliaries
• Office and support loads
• Lighting, controls and other site services

During islanded operation, POI import may fall to zero even though the facility’s underlying electrical demand remains largely unchanged.

Event reports should distinguish three different indicators.

POI Net-Import Reduction

The reduction in electricity imported from the grid during the defined event period.

Gross Facility-Load Reduction

The measured or calculated reduction in separately identified IT, cooling, mechanical and other internal electrical-load categories relative to a defined pre-event reference or another approved attribution method.

Gross facility-load reduction is normally a derived event metric rather than a direct reading from a single meter.

Its calculation may require:

• Separately metered load categories
• A defined pre-event reference
• Expected load under comparable conditions
• Time-aligned IT and cooling data
• Workload and equipment-status records
• An approved attribution method

Onsite-Supply Contribution

The contribution supplied by generators, BESS, PV or other onsite resources.

Assuming that the facility-load reference and the generator and BESS contributions have been independently measured or validated:

POI net-import reduction: 30 MW
Gross facility-load reduction: 5 MW
Generator contribution: 20 MW
BESS contribution: 5 MW

The grid sees a 30 MW reduction, but only 5 MW is attributed to physical facility-load reduction under the defined method.

Reporting only POI reduction may overstate the amount of flexible load that was actually reduced.

The event calculation should use either:

• Gross source output, with the corresponding generator and BESS auxiliaries included in facility demand; or
• Net source contribution after defined auxiliaries and downstream losses have been deducted.

The two approaches should not be mixed, because doing so may double-count auxiliary consumption or electrical losses.

3. Measurement Boundaries Needed During an Event

Emergency-event attribution normally requires multiple coordinated measurement points.

Routine energy meters may support steady-state power, interval energy and cumulative-energy attribution. Fast transfers, synchronisation, protection actions, waveform disturbances and sub-cycle behaviour may require protection relays, sequence-of-events records, disturbance recorders or power-quality analysers.

3.1 POI Import and Export

The POI boundary may provide:

• Grid-import energy
• Grid-export energy
• Net active power
• Reactive power
• Voltage
• Frequency
• Power factor
• POI breaker status where separately available

The meter shows the net grid-facing result. It does not independently identify which internal load, generator or storage resource caused the change.

3.2 Onsite Generator Output

Generator-related measurement may include:

• Generator-terminal output
• Generator switchgear output
• Active and reactive power
• Generated energy
• Voltage and current
• Operating duration
• Generator auxiliary consumption
• Breaker and synchronisation status

The exact meter location matters. A meter at the generator terminals will not produce the same net contribution as a meter downstream of auxiliaries, transformers and feeders.

For multiple generators operating in parallel, the project may also require:

• Individual generator output
• Aggregated output
• Start-command time
• Synchronisation time
• Breaker-close time
• Unit loading profile
• Unit trip or shutdown time
• Generator availability

3.3 BESS AC and DC Boundaries

A project may require separate battery and Power Conversion System (PCS) boundaries.

The battery DC boundary may include:

• DC voltage
• DC current
• Battery-side power
• DC charge and discharge energy
• Battery-side throughput

The PCS AC boundary may include:

• AC charge energy
• AC discharge energy
• Active and reactive power
• Voltage
• Current
• Frequency
• Power factor

Battery DC energy, PCS AC energy and POI energy should not be treated as interchangeable.

3.4 UPS Input, Output and Bypass Paths

UPS measurement may need to distinguish:

• Rectifier input
• Bypass input
• UPS output
• Battery-discharge status
• Normal double-conversion operation
• Bypass operation
• Static Transfer Switch (STS) status
• Input-source identification where available
• Conversion losses

UPS input–output differences should not automatically be interpreted as battery contribution. They may also reflect conversion losses, bypass operation, different measurement locations or timing misalignment.

3.5 Critical IT Load

Critical-load measurement should identify the circuits that must remain energised during the event.

Depending on the architecture, the project may measure:

• Critical IT halls
• Network and security systems
• Selected UPS output buses
• Essential control systems
• Priority computing clusters

3.6 Cooling and Interruptible Auxiliary Loads

Separate measurement may be required for:

• Essential cooling
• Redundant or non-critical cooling
• Chillers, pumps and fans
• Office and support loads
• Deferred computing workloads
• Interruptible auxiliary equipment
• Battery or generator auxiliaries

4. Critical, Non-Critical and Interruptible Loads

Not every data-center load has the same operational priority.

Relevant categories may include:

• Critical IT load
• Essential cooling
• Network and security systems
• UPS and control equipment
• Non-critical cooling capacity
• Redundant mechanical equipment
• Office and support loads
• Battery charging
• Deferred computing workloads
• Interruptible or transferable loads

The measurement architecture should help answer:

• Which load category actually decreased?
• Did the reduction affect critical equipment?
• How long was it maintained?
• Was the reduction continuous or intermittent?
• Did cooling demand increase later?
• Did recovery create a new POI peak?

A decrease in computing workload is not automatically equivalent to an immediate electrical-load reduction. The relationship may depend on server utilisation, cooling response, workload scheduling and the time required to power down or redistribute equipment.

Formal demand-response or grid-service programmes may require separate baseline, activation, measurement-and-verification, eligibility and settlement rules. This article focuses on physical event attribution rather than programme settlement.

5. How Backup Generators Change the Energy Balance

A backup generator can reduce POI import while the data center’s underlying facility demand remains unchanged.

The project should confirm whether the generator meter is installed at:

• Generator terminals
• Generator switchgear
• The downstream side of a unit transformer
• UPS input bus
• Critical-load bus
• Main facility bus

A simplified net-contribution relationship is:

Net generator contribution
=
generator-terminal output
− generator auxiliaries
− defined transformer and feeder losses

The actual calculation depends on the selected boundaries.

Internal generator-controller values may support operation and diagnostics, but they should not automatically be treated as independent billing, settlement or event-verification measurements.

Standard energy meters may record steady-state power and energy. Generator starting transients, synchronisation, transfer behaviour, protection operation and waveform events normally require specialised event or protection records.

6. How BESS Changes POI Load

Battery operation can affect POI demand in both directions.

During discharge:

BESS discharge → lower grid import

During charging:

BESS charging → higher grid import

Battery discharge can reduce POI demand without reducing the data center’s underlying IT or cooling load.

Projects should distinguish between:

• UPS batteries
• Centralised site BESS
• Distributed facility-support batteries
• Generator starting batteries

Generator starting batteries should normally be tracked as generator-readiness or auxiliary-system assets rather than counted as a material source of facility-load support, unless the project architecture explicitly uses them for another purpose.

Data responsibilities also differ:

• The Battery Management System (battery BMS) provides battery state, condition and safety data.
• The PCS provides conversion status, operating mode and power-conversion data.
• An energy meter provides electrical measurements at a defined boundary.
• The EMS coordinates power sources and loads.

BESS auxiliary demand should be included when calculating net contribution.

A simplified relationship may be:

Net BESS contribution
=
PCS AC discharge output
− BESS auxiliary consumption
− defined downstream losses

This value should not be inferred from State of Charge alone.

7. What Data Should Be Reported for an Emergency Event?

An event record should cover the full operating sequence:

1. Pre-event
2. Activation
3. Sustained response
4. Release
5. Recovery
6. Recharge or rebound

Event Identification and Authority

• Event identifier
• Instruction or trigger source
• Requested response
• Approval and authority chain
• Operating-mode label
• Site or project identifier

The instruction or trigger source may include:

• PJM or utility instruction
• Site EMS command
• Protection action
• Internal emergency logic

The approval and authority chain should identify the party authorised to request, approve and release the response.

Timing

• Event start and end time
• Pre-event reference period
• Generator start-command time
• BESS dispatch-command time
• UPS transfer time
• Activation time
• Release time
• Recovery start and end
• Battery-recharge period
• Timestamp source
• Time zone or UTC offset
• Clock-synchronisation status

Electrical Measurements

• POI active power
• POI import and export energy
• Generator active power and energy
• BESS charge or discharge power
• UPS input, bypass and output
• Critical-load power
• Cooling-load power
• Auxiliary-load power
• Separately metered load-category power
• Interrupted-circuit power where directly available

Switching and Operating Status

• Interrupted-circuit status
• POI breaker state
• Generator breaker state
• Automatic Transfer Switch (ATS) status
• STS status
• UPS bypass status
• Generator synchronisation status
• BESS operating mode
• Islanded or grid-connected state

Response and Recovery

• Requested response
• Actual POI response
• Calculated facility-load reduction relative to the defined pre-event reference
• Generator contribution
• BESS contribution
• Attribution method and methodology version
• Controller- or model-reported available generator or BESS capability
• Recovery demand
• Battery-recharge power
• Rebound-peak value

Available generator or BESS capability is normally a controller- or model-reported value rather than a direct energy-meter reading.

Data Context

• Event-data interval or sampling period
• Device identifier
• Measurement-point identifier
• Register-map version
• Firmware version
• Calculation-method version

The report should distinguish directly measured, controller-reported and calculated values.

8. Data-Origin and Quality Status Should Be Separate

Data status should not be stored as one mutually exclusive quality field.

A record may therefore be:

Actual + Available + Validated + Corrected

The event-data model should preserve separate fields for:

• Data origin
• Availability
• Validation
• Processing status
• Correction timestamp
• Original-record reference
• Reason for substitution or correction

This is particularly important when event data is reconstructed after a communication interruption.

9. Data Responsibilities Across Metering, DCIM and Control Systems

The term BMS can be ambiguous.

In this article:

• Battery BMSmeans Battery Management System.
• Building BMSmeans Building Management System.

No single device provides the complete event record. The project should define a source of truth for each measurement, status and calculated result.

10. Common Attribution Errors

Common mistakes include:

1. Treating the entire POI reduction as load curtailment
2. Treating gross facility-load reduction as a direct single-meter value
3. Failing to distinguish actual load reduction from onsite supply
4. Mixing gross source output and net source contribution in one calculation
5. Treating generator-controller values as independent settlement data
6. Combining UPS battery operation with site-level BESS dispatch
7. Counting generator starting batteries as material facility support
8. Ignoring generator and BESS auxiliary consumption
9. Failing to separate IT and cooling loads
10. Ignoring UPS bypass and conversion losses
11. Using inconsistent timestamps across meters, EMS and DCIM
12. Mixing normal, emergency, islanded and recovery records
13. Reversing import/export or charge/discharge direction
14. Failing to record ATS, STS and breaker status
15. Using interval meter data to interpret sub-cycle transfer events
16. Ignoring the rebound peak and battery recharge after release
17. Reporting POI reduction without documenting the attribution method

11. Buyer Checklist for Emergency-Operation Metering

Projects participating in demand response, emergency programmes or ancillary services should separately confirm baseline, activation, measurement-and-verification, settlement and eligibility requirements.

12. How YTL Can Support Initial Meter Evaluation

Zhejiang Yongtailong Electronic Co., Ltd. (YTL) can support the initial evaluation of selected CT-operated meters, panel meters, multifunction meters, DIN-rail meters, AC energy meters, selected DC meters and communication-enabled metering products for data-center feeders, backup-power systems, UPS-related circuits and BESS measurement points.

Depending on the selected model and customer requirements, YTL can support:

• Initial meter-model selection
• Voltage and current-range review
• Initial technical discussion of customer-proposed measurement points, intended electrical boundaries and data purposes
• Review of customer-proposed CT ratios, shunt inputs and meter-side sensing requirements
• Import/export and charge/discharge direction review
• RS485 and Modbus option confirmation
• Register-map, unit, scaling, data-type and byte-order review
• Sample-level meter-to-gateway interface evaluation
• Review of the proposed meter-to-EMS or meter-to-DCIM interface

Event-data resolution, internal refresh rate, interval storage and timestamp functions vary by model and should be confirmed separately from communication polling frequency.

Communication functions, measurement intervals, accuracy, certification scope and platform compatibility must be confirmed for the selected model and intended use.

YTL does not define:

• The project POI, revenue-metering or settlement boundary
• Emergency-event attribution methodology
• Flexible-load baseline
• Generator-dispatch eligibility
• PJM, DOE or utility emergency-programme qualification
• UPS or ATS/STS transfer logic
• Protection coordination
• Generator environmental-permit compliance
• Demand-response or ancillary-service measurement and settlement
• Final commissioning or event acceptance

These matters remain the responsibility of the data-center owner, project engineer, utility, transmission or distribution operator, generator and UPS suppliers, EMS/DCIM providers, protection engineer, programme administrator and other relevant contractual or regulatory parties.

YTL supports selected field-level electrical-measurement and data-output applications, subject to confirmation of the selected model, measurement interval, electrical boundary, communication interface, register-map version and intended data use.

Conclusion

During a grid emergency, a data center’s POI demand may change because of calculated facility-load reduction, backup generation, battery discharge, source transfer or several actions occurring together.

POI data alone cannot identify the cause.

A reliable event-measurement architecture should distinguish:

• POI net-import reduction
• Calculated gross facility-load reduction
• Generator contribution
• BESS contribution
• UPS source and operating mode
• Critical IT load
• Cooling and mechanical demand
• Interruptible loads
• Auxiliary consumption
• Switching and protection status
• Recovery and rebound demand

Emergency-period metering should explain not only how much POI demand changed, but also which load, resource or switching action created that change.

Clear electrical boundaries, time-aligned records, defined source-of-truth responsibilities and an approved attribution method allow operators to reconstruct events without confusing onsite supply with physical load reduction.

References

1. PJM Interconnection, Request for Backup Generation Emergency Order Under Federal Power Act Section 202(c), 27 June 2026.
2. S. Department of Energy, Energy Secretary Secures Mid-Atlantic Grid Ahead of Period of Hot Weather, 30 June 2026.
3. PJM Interconnection, Manual 13 Revision 98 Stakeholder Materials—Attachment O: Emergency Use of Back-up Generators, June 2026.
4. PJM Interconnection, Powering Reliability Through Market Design, 6 May 2026.
5. PJM Interconnection, Notice Regarding Behind the Meter Emergency Procedure, 29 January 2026.