Bus Duct vs Cable Tray: Cost Comparison for Electrical Estimators

The Decision Point: When Bus Duct Makes Sense

Bus duct (also called busway) is a factory-assembled, metal-enclosed conductor system used to distribute high-current electrical power. It is the standard approach for feeder runs on commercial buildings and industrial plants at current levels above 800–1000A, where the alternative — multiple parallel cable runs in conduit or tray — becomes expensive, bulky, and labour-intensive to terminate.

The fundamental economics of bus duct vs cable shift depending on:

• Current level: Bus duct becomes cost-competitive above 800A and generally more economical above 1200A for run lengths greater than 15–20 metres
• Run length: Longer runs favour bus duct (the fixed cost of the end connections is amortised over more metres); short runs often favour cable (the bus duct fixed connection costs dominate)
• Number of taps: Bus duct with bus plugs allows taps to be made anywhere along the run without field splicing — a significant advantage in industrial facilities with distributed loads
• Future flexibility: Cable is easier to reroute; bus duct is fixed once installed but can be reconfigured by adding bus plugs
• Available space: Bus duct has a small cross-sectional footprint for its current capacity; multiple parallel cable runs in conduit or tray can consume significant ceiling or floor space

Bus Duct Types and Their Cost Profiles

Not all bus duct is the same, and the type significantly affects the price:

Feeder Busway

Point-to-point feeder busway — from a switchboard or transformer to a downstream panel or switchboard. No intermediate taps. The most economical bus duct type. Used for high-current trunk feeders in commercial and industrial buildings. Copper feeder busway at 1600A is typically priced at $250–$500 per metre for straight sections, plus end connections ($500–$1,500 per end), elbows ($800–$2,500 each), and offset sections ($1,000–$3,000 each).

Plug-In Busway

Busway with regularly spaced openings where bus plug units (essentially fusible switches or circuit breakers in a plug-in enclosure) can be inserted anywhere along the run. This is used in industrial facilities to feed equipment at any point along the bus duct, avoiding separate feeder cables from a remote panel. Plug-in busway is 15–25% more expensive than feeder busway per metre due to the additional manufacturing required for the plug-in apertures. Bus plug units themselves range from $500 to $5,000+ depending on current rating and type of overcurrent protection.

Lighting Busway

Low-current (typically 60A or less per phase) busway for lighting and power track systems. Not relevant for main distribution, but commonly used in commercial buildings for pendant lighting and small power outlets. Priced at $30–$100 per metre depending on current rating and enclosure type.

The Cable Alternative: True Installed Cost

The common mistake in bus duct vs cable comparisons is comparing bus duct supply-only price against cable supply-only price. The correct comparison is total installed cost for each option. For large cable runs, total installed cost includes:

• Cable material: At 1600A, the cable requirement is typically 3–4 parallel conductors of 500–750MCM per phase. At 2026 copper prices, 750MCM cable is approximately $85–$120 per metre per conductor — for a 3-phase + neutral installation with 4 parallels, the cable material alone is $1,000–$1,500 per metre of run.
• Conduit or tray: 4 parallel sets of 750MCM require significant conduit (multiple 4" conduits per phase) or a large cable tray system — typically 600mm wide tray or larger
• Support structure: Large cable tray requires more frequent structural support than bus duct
• Installation labour: Pulling large cables in parallel through conduit is labour-intensive. Terminating 750MCM cable requires heavy crimp tooling and specialist labour.
• Lugs and terminations: Large copper compression lugs at the switchboard and downstream termination points — typically $50–$200 per lug, multiplied by the number of conductors per phase and the number of termination points
• Cable tray covers and closures: Required at penetrations and in exposed areas

When all these items are included, the total installed cost of cable for a 1600A feeder run in the 20–50 metre range is often comparable to or higher than the equivalent bus duct installation — particularly in commercial buildings with limited ceiling space that would require extensive conduit banking.

Practical Cost Comparison: 1600A, 30-Metre Run

A worked example for a 30-metre, 1600A, 480V 3-phase feeder (indicative 2026 pricing, supply and install):

Note: Indicative 2026 pricing. Actual costs vary by region, contractor, copper price at time of procurement, and specific project conditions.

Lead Time: The Bus Duct Constraint

The primary practical disadvantage of bus duct is lead time. Bus duct is factory-manufactured to the project's specific dimensions and routing — straight sections, elbows, offsets, and end connections are all sized to the actual installation. Lead times for custom bus duct:

• Standard feeder busway (copper, 800A–2500A, straight sections): 8–14 weeks
• Custom bus duct with elbows, offsets, and special configurations: 12–20 weeks
• Plug-in busway systems: 10–18 weeks

Cable, by contrast, is available off-the-shelf or within 2–4 weeks for large conductor sizes. If the project program is tight and the bus duct lead time would be critical path, cable may be the only practical choice regardless of the cost comparison — or an early bus duct order needs to be placed before full construction drawings are available.

Aluminium vs Copper Bus Duct

Bus duct is available in both copper and aluminium conductor versions. Aluminium bus duct is typically 20–35% cheaper than copper and is used on most commercial distribution applications where weight and the aluminium conductor corrosion risk can be managed. Copper bus duct is specified where space is limited (copper busbars can be smaller for the same current capacity), in corrosive environments, or where project specifications explicitly require copper.

When pricing bus duct, confirm the conductor material required by the specification before obtaining quotes — a copper bus duct quote and an aluminium bus duct quote are not interchangeable in a bid.

When Cable Is Still the Right Answer

Despite bus duct's cost advantage at high currents and long runs, there are situations where cable in tray or conduit remains the better choice:

• Short runs (under 15 metres): the bus duct end connection costs dominate and cable is cheaper
• Outdoor or wet-location runs: standard indoor bus duct is not suitable, and outdoor-rated busway has a significant price premium
• Complex routing with many direction changes: every bus duct elbow or offset is a factory-manufactured item with a long lead time; cable is more flexible for complex routes
• Projects with tight programs where bus duct lead times would be critical path
• Retrofit projects where the existing cable route is already established and adding a bus duct run would require structural modifications

Conclusion

The bus duct vs cable decision for high-current feeder runs is primarily an economics question — but it requires comparing total installed cost, not just per-metre material cost. At 1200A and above for runs greater than 20 metres, bus duct is frequently more cost-effective than the cable alternative when all materials and installation labour are properly accounted. The constraints are lead time and routing flexibility. Estimators who build both options into their comparison at the design stage give the project team the information to make a sound decision — rather than defaulting to cable because it is familiar or to bus duct because someone specified it without checking the numbers.