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How this applies to an existing Portfolio Lighting installation

This ASHRAE 90.1 Exterior Lighting Requirements: Power Limits, Zones and Automatic Controls resource can help when inspecting, repairing or extending Portfolio outdoor lighting. First identify the transformer, its supply connection, the existing cable and the fixture locations; requirements depend on the equipment listing, installation conditions and locally adopted rules.

Portfolio owner’s first step: For Portfolio equipment, compare the actual nameplate and installation instructions with the safety topic below before altering the system.

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Quick Answer: What Does ASHRAE 90.1 Require for Exterior Lighting?

For most covered commercial sites, Standard 90.1 limits installed exterior lighting power and requires specific automatic control functions. The exact power allowance depends on the exterior application and the site's exterior lighting zone.

Power LimitInstalled exterior lighting power cannot exceed the applicable exterior lighting power allowance.

Lighting ZoneThe allowable power depends in part on the exterior lighting zone assigned to the project.

Automatic ControlsApplicable exterior lighting must respond to daylight and, depending on use, schedules or occupancy.

2025 EditionThe current edition revises exterior power densities, lighting zones and control requirements.

Think of 90.1 as a lighting energy budget. A project can have excellent photometrics and still fail 90.1 if it installs too much connected wattage or lacks required controls. It can also meet the wattage budget and still be a poor lighting design if glare, visibility or accessibility are ignored.

What Buildings and Sites Does Standard 90.1 Cover?

ASHRAE describes Standard 90.1 as the energy standard for sites and buildings except low-rise residential buildings. It establishes minimum energy-efficiency requirements for new sites and buildings, new portions of buildings and their systems, and new systems and equipment installed in existing buildings.

In practical exterior-lighting terms, this commonly matters for offices, retail properties, schools, campuses, hospitals, warehouses, industrial sites, hotels, restaurants, multifamily buildings above the low-rise residential scope, parking areas and other commercial/institutional properties.

Adoption matters. The newest ASHRAE edition is not automatically enforceable everywhere on its publication date. A state, city or other authority may adopt Standard 90.1 directly, adopt an energy code based on it, amend it, or still enforce an earlier edition. Always identify the locally adopted energy code before doing a compliance calculation.

What Changed for Exterior Lighting in ASHRAE 90.1-2025?

ASHRAE says the 2025 edition incorporates 105 addenda and continues to raise energy efficiency for commercial buildings and sites. Section 9 received several changes that directly affect exterior lighting.

Power

Updated Exterior Lighting Power Densities

The allowed connected power for exterior applications has been updated to reflect current LED technology and modern practice.

Zones

Revised Exterior Lighting Zones

ASHRAE says the 2025 lighting zones were revised to align with current IES guidance.

Controls

Stronger Automatic Control Requirements

Control provisions were strengthened through revised thresholds and expanded control requirements.

Organization

Power and Controls Are More Clearly Separated

Section 9 was restructured so designers can distinguish lighting power-density limits from mandatory control functions more easily.

This is important for 2026–2027 projects because specifications copied from an older 2019 or 2022 workflow may no longer match the current 2025 organization, lighting-zone framework or power limits.

Apply this requirement to an existing Portfolio installation

Apply ASHRAE 90.1 Exterior Lighting Requirements: Power Limits, Zones and Automatic Controls to the actual installation conditions rather than treating a general lighting rule as a product specification. Document whether the equipment is indoors or outdoors, wet/damp exposure, supply voltage, wiring method, mounting location, and the listing/markings on the installed equipment. Those facts determine which requirements are relevant and also help separate code compliance from manufacturer instructions and replacement-part compatibility. Use Portfolio Parts for the next installation-specific check.

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Exterior Lighting Power Allowance: The Core 90.1 Calculation

Standard 90.1 establishes an exterior lighting power allowance (LPA). The basic compliance concept is straightforward:

Installed Exterior Lighting Power ≤ Exterior Lighting Power Allowance

The allowance is assembled from the applicable exterior-lighting categories for the project and the applicable exterior lighting zone. The installed wattage must then be calculated according to the standard's luminaire-wattage rules.

The calculation is not simply “total site square footage × one watt-per-square-foot number.” Different exterior applications are treated separately. Examples include parking and drives, building grounds, walkways, plazas, ramps, entrances, exits, loading areas, canopies, sales areas, façade lighting and other specific exterior uses.

Why this catches projects by surprise

Do not use this page as a substitute for the official allowance tables. ASHRAE's numerical exterior-lighting power tables are copyrighted and edition-specific. For a permit calculation, use the exact locally adopted edition and the official table applicable to the project.

Tradable vs Non-Tradable Exterior Lighting: Why the Category Matters

One of the most useful concepts in Standard 90.1 is that some exterior-lighting allowances can be traded among permitted exterior applications while others are treated more specifically.

That means a designer cannot assume unused wattage from one category can automatically be moved to any other exterior feature. The project's exterior lighting schedule should identify each application, its applicable allowance and whether the standard permits that allowance to participate in a trade-off.

High-information-gain design habit: Build the compliance worksheet by application first—parking, walkway, entrance, façade, landscape, canopy—before summing anything. That makes accidental cross-category trading much easier to catch.

ASHRAE 90.1 Exterior Lighting Zones 0 Through 4

The exterior lighting zone establishes the expected nighttime luminous context of the site. The 2025 edition revised the zone framework to align with current IES guidance.

Lighting Zone General Nighttime Context Typical Direction Why It Matters to 90.1 LZ0Very dark / undeveloped environmentAreas where electric lighting is extremely limited or highly constrainedLowest exterior-lighting energy expectation LZ1Low ambient-light environmentRural or low-activity developed settingsLower allowances than brighter urban contexts LZ2Moderate ambient-light environmentResidential mixed-use, neighborhood business and moderate-activity institutional settingsCommon zone for many suburban properties LZ3Higher ambient-light environmentActive commercial and urban environmentsReflects a brighter existing nighttime context LZ4Very high ambient-light environmentSpecial high-activity metropolitan districts designated by local authorityNot a zone designers should self-select merely to obtain more wattage

Swipe horizontally to see the full lighting-zone table.

Lighting zone is a site-context decision, not a design preference. You should not move a project from LZ2 to LZ3 or LZ4 because the proposed fixture package needs more power. The local jurisdiction may also specify the applicable zone.

For the pedestrian-design side of lighting zones, see our ANSI/IES RP-43-25 Guide.

Exterior Lighting Controls: The Other Half of 90.1 Compliance

Meeting the lighting power allowance is not enough. Exterior lighting must also implement the control functions required for the application.

Control Function What It Does Why It Saves Energy Typical Example OFF controlProvides a way to turn the exterior lighting offPrevents lighting from being permanently energizedAutomatic control system or time-based control Daylight OFFAutomatically turns applicable lighting off when daylight is sufficientPrevents exterior lights from operating during the dayPhotocell or astronomical control strategy Scheduled OFFTurns applicable lighting off during defined nonoperating periodsEliminates unnecessary all-night operationTime clock / building control system Scheduled reductionAutomatically reduces connected power during late-night or nonoperating periodsMaintains some light while cutting energy useDim-to-50% strategy where permitted/required Occupancy reductionReduces lighting when no activity is detectedMatches output to actual site useParking-area luminaires with occupancy sensors

Swipe horizontally to see the complete control table.

Earlier 90.1-2022 addenda that fed into the 2025 edition illustrate the direction of the current standard: automatic daylight shutoff, late-night/off-hour reduction, and occupancy-based power reduction are central exterior-lighting energy strategies.

Daylight Shutoff: Exterior Lights Should Not Burn Through the Day

One of the clearest exterior-control principles in Standard 90.1 is that applicable exterior lighting should automatically turn off when sufficient daylight is available.

This is not the same thing as merely giving the building manager a manual switch. The energy standard expects automatic operation so a forgotten switch does not leave parking, façade or site lighting energized all afternoon.

Common control methods

Commission the control after installation. A photocell facing a bright wall, installed under a canopy, or illuminated by the fixture it controls can create false switching behavior even when the specification is technically correct.

Parking Lot Lighting: Power Allowance + Controls + Actual Lighting Design

Parking lots are one of the best examples of why three different rule sets need to be kept separate:

Energy

ASHRAE 90.1

Limits connected lighting power and requires applicable automatic controls.

Photometrics

ANSI/IES RP-8

Addresses roadway and parking-facility lighting performance and design considerations.

Accessibility

ADA

Addresses accessible parking, access aisles, routes and physical accessibility—not a universal parking-lot foot-candle number.

Electrical Safety

NEC

Addresses wiring methods, branch circuits, grounding, GFCI where applicable and safe electrical installation.

For the accessibility side, see the Parking Lot Lighting ADA Guide. For standards selection, see the Outdoor Lighting ANSI Standards Guide.

Why Parking-Lot Occupancy Controls Matter

Modern LED parking-area lighting can respond quickly to occupancy, which makes large all-night parking areas a major opportunity for energy reduction. Standard 90.1 has progressively strengthened controls for exterior areas, including occupancy-based reductions for qualifying parking applications.

The key design challenge is not simply installing a motion sensor. The control zones, sensor coverage, mounting height, detection pattern, grouping of luminaires and minimum dim level all need to work together.

Do not use occupancy dimming to create unsafe visual discontinuities. Energy compliance and visual design must be coordinated. A compliant control strategy should not create a patchwork of harsh bright and dark zones that makes drivers or pedestrians less comfortable.

Walkways, Plazas, Ramps and Campus Paths

Standard 90.1 has expanded its exterior-lighting scope over time to cover more site applications, including campus walkways and parking areas that serve building occupants even when the lighting is not necessarily powered from the building service itself.

That matters for schools, universities, hospitals, corporate campuses and large institutional properties where lighting may be distributed across separate electrical services.

For a walkway project, ask four separate questions

  1. Does 90.1 apply? Determine adopted energy-code scope.
  2. What exterior lighting zone applies?
  3. What power allowance and controls apply to this exterior application?
  4. What IES/ADA criteria govern actual nighttime visibility and accessibility?

For pedestrian applications, our ANSI/IES RP-43-25 Guide explains the design side. For school properties, see School Campus Lighting Accessibility.

Inspect the Portfolio power source and outdoor cable route

Apply ASHRAE 90.1 Exterior Lighting Requirements: Power Limits, Zones and Automatic Controls to the actual installation conditions rather than treating a general lighting rule as a product specification. Document whether the equipment is indoors or outdoors, wet/damp exposure, supply voltage, wiring method, mounting location, and the listing/markings on the installed equipment. Those facts determine which requirements are relevant and also help separate code compliance from manufacturer instructions and replacement-part compatibility. Use Portfolio Parts for the next installation-specific check.

landscape lighting electrical safety Portfolio landscape lighting Portfolio troubleshooting

Does ASHRAE 90.1 Apply to Landscape Lighting?

It can. On covered commercial sites, exterior lighting power provisions can apply to building grounds and landscape-related lighting applications included within the standard's scope.

This is where residential landscape-lighting habits can cause trouble on a commercial project. A designer accustomed to adding uplights until the property “looks right” may unintentionally exceed the site's available lighting power or overlook required controls.

Commercial landscape lighting needs an energy budget. On a covered project, every decorative tree light, façade luminaire, path fixture and site feature should be categorized before the final fixture schedule is approved.

Façade and Decorative Lighting Are Not an Unlimited Bonus

Architectural façade lighting often feels separate from “functional” site lighting, but Standard 90.1 still treats exterior decorative lighting as an energy use that must be addressed under the applicable allowance and control rules.

The 2025 edition specifically notes revised decorative and specialty lighting values to reflect widespread LED adoption. That means an older design rule based on legacy lamp technology may overstate the amount of power needed today.

How Installed Luminaire Wattage Is Counted

A common compliance mistake is using the wattage you expect the luminaire to operate at instead of the wattage the standard tells you to use for the calculation.

Standard 90.1 includes rules for determining the wattage of installed lighting equipment, including luminaires with integral drivers, field-adjustable settings, track systems, low-voltage systems and retrofitted luminaires.

Field-adjustable fixtures deserve special attention. If a luminaire can be field-set to multiple wattages or lumen packages, confirm which value the adopted edition requires for the compliance calculation. Do not assume a lower commissioning setting automatically lets you count only that lower wattage.

Exterior Lighting Alterations and Retrofits

Standard 90.1 also contains requirements for lighting alterations in existing buildings and exterior areas. The compliance path can depend on the scope of the alteration and the amount of lighting being changed.

This matters for LED conversions because “we are only replacing old fixtures” does not automatically mean the project is exempt from energy-code power or control requirements.

Before a retrofit, document

Exemptions and Special Applications: Do Not Assume Every Exterior Watt Is Counted the Same Way

Standard 90.1 includes exemptions and special treatment for certain exterior-lighting applications. The exact list is edition-specific, which is another reason permit calculations should use the official adopted standard rather than a generic online wattage chart.

Examples in energy codes can include lighting tied to specific safety, transportation, signage, temporary, specialized or regulated functions. Whether an application is exempt from the power allowance does not necessarily mean it is exempt from every other code or control requirement.

ASHRAE 90.1 vs NEC vs IES: Which Rule Answers Which Question?

Question Primary Standard / Code What It Answers How much exterior lighting power can the project install?ASHRAE 90.1 / adopted energy codeEnergy budget and power allowance When must exterior lights shut off or dim?ASHRAE 90.1 / adopted energy codeMandatory lighting controls How should parking lots and roads be illuminated?ANSI/IES RP-8Roadway and parking-facility lighting design How should pedestrian outdoor spaces be illuminated?ANSI/IES RP-43Pedestrian vision, glare, lighting zones and outdoor-lighting quality How should landscape features be illuminated?ANSI/IES RP-47Landscape-lighting design guidance How must wiring and electrical equipment be installed?NEC / locally adopted electrical codeElectrical installation safety How must accessible parking/routes be physically configured?ADA / accessibility codePhysical accessibility

Swipe horizontally to see the complete standards comparison.

ASHRAE 90.1 Is Not a Dark-Sky Standard—but the Goals Can Reinforce Each Other

Energy efficiency and dark-sky performance are different compliance questions. Standard 90.1 focuses on energy use, while dark-sky ordinances and IES guidance may address uplight, glare, light trespass, spectrum, curfews or environmental effects.

However, the goals often align. Lower connected power, automatic shutoff, scheduled reduction and occupancy-based controls can reduce unnecessary nighttime light as well as energy use.

See our Dark-Sky Compliance vs Certification Guide for the environmental-compliance side.

Why a Photometrically Good Project Can Still Fail Energy-Code Inspection

A project can hit every target illuminance value and still fail its energy-code review because:

Repair Portfolio fixtures without assuming every part is interchangeable

Apply ASHRAE 90.1 Exterior Lighting Requirements: Power Limits, Zones and Automatic Controls to the actual installation conditions rather than treating a general lighting rule as a product specification. Document whether the equipment is indoors or outdoors, wet/damp exposure, supply voltage, wiring method, mounting location, and the listing/markings on the installed equipment. Those facts determine which requirements are relevant and also help separate code compliance from manufacturer instructions and replacement-part compatibility. Use Portfolio Parts for the next installation-specific check.

Portfolio replacement parts Portfolio outdoor lighting Portfolio model lookup

ASHRAE 90.1 Exterior Lighting Compliance Checklist

Identify the adopted edition

Confirm whether the jurisdiction uses 90.1-2025, 90.1-2022, another edition or an energy code based on it.

Determine project scope

New building, new site, addition, retrofit or exterior-lighting alteration.

Assign the exterior lighting zone

Use the applicable standard and local jurisdiction designation.

Inventory every exterior lighting application

Parking, drives, walks, ramps, entrances, canopies, façade, landscape and specialty areas.

Calculate the exterior lighting power allowance

Use the official table from the adopted edition.

Calculate installed wattage correctly

Apply the standard's wattage rules for each fixture type.

Verify trade-offs

Do not move unused allowance between categories unless the standard permits it.

Map required control functions

Daylight OFF, scheduled OFF/reduction and occupancy reduction as applicable.

Commission controls

Verify sensors, schedules, astronomical controls and dimming behavior in the field.

Then verify NEC and IES design requirements separately

Energy compliance is only one layer of a complete exterior-lighting design.

Why ASHRAE 90.1-2025 Will Matter More in 2027

The 2025 edition is new enough that many jurisdictions, design standards, specifications and online articles will still reference older editions during 2026 and 2027. That transition creates a practical compliance problem: a designer may be reading 2025 guidance while the local permit office still enforces 2022 or an earlier code.

The right question is therefore not simply “What does the newest ASHRAE standard say?” but:

Which edition is legally adopted for this project, and what does the current 2025 edition change for future work?

That edition-aware approach is especially important for exterior lighting because the 2025 standard revises lighting zones, exterior lighting power densities and control requirements.

Official Sources and Verification

This guide summarizes publicly described features of the current standard without reproducing ASHRAE's copyrighted numerical tables or proprietary text.

For permit or design calculations: Obtain the official edition adopted by the authority having jurisdiction. Do not rely on an online summary for exact wattage allowances, exceptions or mandatory-control tables.

Related Exterior Lighting Compliance Guides

ASHRAE 90.1 Exterior Lighting FAQ

What is the current edition of ASHRAE 90.1?

ANSI/ASHRAE/IES Standard 90.1-2025 is the current edition. ASHRAE says it incorporates 105 addenda and updates exterior lighting power densities, lighting zones and control requirements.

Does ASHRAE 90.1 apply to residential landscape lighting?

Standard 90.1 is primarily an energy standard for sites and buildings except low-rise residential buildings. Ordinary detached-house landscape lighting generally falls outside its basic building scope, but commercial, institutional and many multifamily sites can be covered.

Does Standard 90.1 limit exterior lighting wattage?

Yes. Covered exterior lighting must comply with the applicable exterior lighting power allowance. The exact allowance depends on the application, lighting zone and adopted edition.

Do exterior lights have to turn off during the day?

Applicable exterior lighting is subject to automatic daylight shutoff requirements. Specific control functions and exceptions must be checked in the adopted edition.

Does 90.1 require parking-lot lights to dim?

Parking-area lighting can be subject to occupancy-based or scheduled power-reduction requirements depending on the application and adopted edition. Use the official control table for the project.

What are ASHRAE exterior lighting zones?

Exterior lighting zones describe the nighttime luminous context of the site, ranging from very dark environments to specially designated high-activity metropolitan areas. The zone affects exterior lighting power allowances.

Is ASHRAE 90.1 the same as IES RP-43?

No. Standard 90.1 is an energy standard. RP-43 is an outdoor pedestrian-lighting recommended practice addressing visibility, glare, lighting zones and design quality.

Does ASHRAE 90.1 replace the NEC?

No. Standard 90.1 addresses energy efficiency. NEC requirements still govern electrical installation safety.

Can a project comply with 90.1 and still have bad lighting?

Yes. Meeting an energy budget does not guarantee good photometrics, low glare, accessibility or appropriate fixture placement. Those must be designed separately.

Which 90.1 edition should I use for a permit?

Use the edition adopted by the state or local authority for that project, including applicable local amendments. The newest published edition is not automatically the enforceable edition in every jurisdiction.

Bottom Line

ASHRAE 90.1 exterior-lighting compliance is built around three decisions: classify the exterior application, determine the correct lighting zone, and provide both an acceptable power budget and the required automatic controls.

The 2025 edition makes this even more important by updating exterior lighting power densities, revising lighting zones to align with current IES guidance and strengthening control requirements. For a complete project, pair 90.1 energy compliance with NEC electrical safety, IES lighting-performance guidance, accessibility requirements and any local dark-sky or light-trespass ordinance.

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