Emergency Lighting Calculator

Emergency Lighting Design Guide for AS/NZS 2293.1

Emergency lighting is a life safety system that provides illumination on escape routes when the normal mains supply fails. In Australia and New Zealand, emergency lighting design, installation, and maintenance are governed by AS/NZS 2293.1 (design and installation) and AS/NZS 2293.2 (inspection and maintenance). The standard applies to all buildings required by the Building Code of Australia (BCA) to have emergency lighting, including commercial offices, retail premises, hospitals, aged care facilities, multi-storey residential buildings, and places of public assembly. This calculator helps you estimate the number of emergency luminaires required for a given floor area, the placement of illuminated exit signs, and the battery capacity needed to maintain the required light levels for the full 90 minute duration.

Key concepts

• Minimum illumination levels. AS/NZS 2293.1 requires a minimum of 0.2 lux on the floor along the centre line of escape routes, and 1 lux at changes of direction, intersections, stairways, and within 2 metres of exit doors. These levels must be achieved at the end of the rated battery duration (90 minutes), not just at initial switch-on when lumen output is highest.
• Maintained vs non-maintained luminaires. Maintained emergency luminaires operate continuously as part of the normal room lighting and switch to battery power during a mains failure. Non-maintained luminaires are off during normal operation and activate only when the supply fails. AS/NZS 2293.1 requires maintained luminaires in places of public entertainment such as cinemas, theatres, and concert venues.
• Battery duration and sizing. The minimum battery duration is 90 minutes for most occupancies. The battery must be sized to deliver the required lumen output for the full duration at end-of-life capacity (typically 80 percent of initial capacity after 4 years). Central battery systems and individual self-contained luminaires are both acceptable, with different trade-offs in maintenance and reliability.
• Exit sign requirements. Illuminated exit signs must be installed at every required exit and along escape routes so that at least one sign is visible from any point on the path of travel. Signs must comply with AS/NZS 2293.1 and the BCA for size, pictogram design (running man), colour (green and white), and mounting height. Photoluminescent signs are permitted only in specific low-risk occupancies.

Common scenarios

1. Multi-storey office building. A 10-storey office tower with open plan floors, fire stairs, and a basement car park. Emergency luminaires are required in all corridors, stairwells, lobbies, and the car park. Exit signs are placed at each stairwell entry, lift lobby, and floor exit. The fire stairs typically require higher illumination (1 lux minimum on treads) because occupants are moving on uneven surfaces. Self-contained luminaires with individual batteries are common for office fitouts because they avoid the cost of running dedicated wiring back to a central battery room.
2. Hospital or aged care facility. Healthcare buildings have extended duration requirements and higher illumination levels in patient care areas. Staff must be able to read medication labels and operate equipment during a power failure. Central battery systems with monitored circuits are preferred for reliability, and the testing regime under AS/NZS 2293.2 is more stringent due to the vulnerable occupant population.
3. Retail shopping centre. Large open floor plates with high ceilings and multiple exit paths. The challenge is achieving 0.2 lux across wide open areas where luminaire spacing must account for the ceiling height and beam spread. Exit sign placement must ensure visibility above shelving and display fixtures. Places of public entertainment within the centre (such as cinemas) require maintained emergency luminaires.

Parameters

Every field this calculator accepts, what it means, the range it accepts, and how it feeds the result. Nothing else is used: if a factor is not in this list, the calculator does not know about it.

Building type (commercial, industrial, residential, assembly)

A coarse occupancy risk category. It applies a multiplier to the exit sign count only: residential 0.8, commercial 1.0, industrial 1.2, assembly 1.5. It does not change the luminaire count, the load, or the battery size. If exit signs are turned off, this field has no effect at all.

Floor area (square metres, 10 to 50,000)

Total enclosed floor area served by the emergency lighting system. Drives the area based luminaire count at one luminaire per 10 square metres, and adds one extra exit sign per 2,000 square metres once the area passes 1,000 square metres. Areas above 50,000 square metres raise a warning to zone the system. On any large floor plate this field, not the path length, is what sets the luminaire count.

Number of exits (whole number, 1 to 20)

Count of required exits from the area. Sets the base exit sign count before the area addition and the building type multiplier, and is also the limit for the exit sign coverage check. More than 20 raises a warning to check the building layout.

Path length to exit (metres, 5 to 500)

The longest single travel distance from the furthest occupied point to an exit. This is one route, not the sum of every escape route in the building. It sets the spacing based luminaire count as the path length divided by the 4 metre maximum spacing, rounded up, and it is the numerator in the reported spacing. Above 200 metres the tool warns about intermediate signage; above 500 metres it warns that the travel distance itself needs checking.

Ceiling height (metres, 2 to 15)

Mounting height of the luminaires above the floor. It has one single effect: if the height is greater than 4.0 metres, one extra luminaire is added to the count. Exactly 4.0 metres does not trigger it. Below 2.4 metres and above 10 metres the tool raises warnings about distribution, and above 8 metres it warns about aiming, but none of those warnings change the numbers.

Emergency exit signs required (tick box)

When ticked, exit signs are counted and 2 watts per sign is added to the load. When unticked, the sign count is zero, no sign load is added, and the exit sign coverage check will report a fail whenever the number of exits is 1 or more. Untick it only when you are sizing luminaires alone and intend to ignore that check.

Battery duration (90 or 120 minutes)

Rated emergency operating time. Only these two values are accepted. Each carries a bundled factor that includes the battery ageing allowance: 90 minutes uses 1.5 and 120 minutes uses 2.0. The effective discharge time used in the sizing is therefore 2.25 hours for a 90 minute system and 4.0 hours for a 120 minute system.

Assumptions and limits

This calculator is a sizing estimator, not a lighting design. Here is exactly what it assumes and where it stops.

What it assumes

• A generic LED luminaire of 3 watts and 300 lumens. There is no product selection and no photometric data. Every luminaire in the count is assumed identical. Exit signs are assumed to draw 2 watts each.
• A 24 volt direct current battery system at 85 percent efficiency. Battery current is the total load in watts divided by 0.85 times 24 volts. Capacity is that current times the effective discharge hours, rounded up to the next half amp hour. The result is a nominal amp hour figure. There is no depth of discharge limit, no end of life capacity correction beyond the bundled ageing factor, no temperature correction, and no distinction between sealed lead acid, nickel cadmium or lithium chemistries.
• Luminaire count is the greater of two coarse rules. Path length divided by 4 metres, or floor area divided by 10 square metres, whichever is larger, plus one if the ceiling is over 4 metres. The 10 square metre coverage figure is a rule of thumb held in the engine, not a photometric result, and on large areas it produces counts well above what a proper layout with real photometry would need.
• Illumination outputs are proportional stand ins. Floor level lux is the luminaire count times 30, divided by the floor area, times 0.65. Open area lux is the luminaire count times 0.4. There is no luminaire intensity distribution, no room surface reflectance, no maintenance factor, no spacing to height ratio and no point by point calculation. These numbers indicate whether the count is in the right ballpark; they are not illuminance predictions.
• Spacing is an average, not a layout. The reported spacing is the path length divided by the total luminaire count, so it falls well below 4 metres whenever the area rule dominates. It does not describe where the luminaires actually go.
• The illumination thresholds used in the checks are indicative. The engine holds 1 lux for escape routes and 0.2 lux for open areas. These figures are held in code as indicative values, not transcribed from a licensed copy of AS/NZS 2293.1 Table 3.1. Read the current table before relying on a pass.

What it does not do

• It does not classify the building or determine whether emergency lighting is required at all. That comes from the National Construction Code and the building classification.
• It does not distinguish maintained from non maintained luminaires, or self contained units from a central battery system. The load and battery figures assume one pooled battery at 24 volts.
• It does not place luminaires or signs, check exit sign viewing distances, sign size, mounting height or legend, or verify sight lines around obstructions.
• It does not size the wiring to the luminaires, the submain, the protective devices, or the charger supply, and it does not address the monitoring or testing arrangements required by AS/NZS 2293.2.
• It does not produce a compliance certificate and it is not a substitute for photometric software and a designed layout.

Every result should be checked against the current edition of AS/NZS 2293.1 and AS/NZS 2293.2, and signed off by the person responsible for the installation. Nothing here is validated or certified, and the underlying figures have not been reviewed by a chartered professional engineer.

Worked examples

Three complete runs through the calculator, with every intermediate figure shown, so you can check the tool against your own arithmetic.