If you're comparing 1.5mm² vs 2.5mm² TPS cable, the most obvious difference is conductor size—but that difference affects how the cable may be used in an electrical installation.
Both sizes are commonly encountered by electrical contractors in New Zealand. However, choosing between 1.5mm² and 2.5mm² TPS isn't simply a matter of saying one is for lighting and the other is for power.
The correct cable size depends on the specific circuit and installation conditions.
This guide explains the practical differences between 1.5mm² and 2.5mm² TPS cable and the factors electricians should consider when selecting cable for an installation.
1.5mm vs 2.5mm TPS Cable at a Glance
| 1.5mm² TPS | 2.5mm² TPS | |
|---|---|---|
| Conductor size | 1.5mm² | 2.5mm² |
| Common association | Lighting and selected fixed-wiring circuits | General power and socket-outlet circuits |
| Relative conductor size | Smaller | Larger |
| Typical handling | Smaller and generally easier to route | Larger conductor |
| Selection depends on | Circuit design and installation conditions | Circuit design and installation conditions |
Important: These are general examples rather than cable-sizing instructions. Cable selection should be determined for the actual installation by an appropriately qualified person in accordance with applicable New Zealand electrical requirements.
What Is 1.5mm² TPS Cable?
1.5mm² TPS cable has conductors with a nominal cross-sectional area of 1.5 square millimetres.
It is commonly encountered in New Zealand electrical installations and is often associated with lighting and selected fixed-wiring circuits.
Typical applications may include:
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Lighting circuits
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Switching
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Selected lower-current circuits
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Other fixed-wiring applications where 1.5mm² is appropriate for the circuit design
However, the application name alone doesn't determine whether 1.5mm² cable is suitable.
An electrician still needs to consider the design current, installation method, cable length, voltage drop, protective device and other relevant installation conditions.
What Is 2.5mm² TPS Cable?
2.5mm² TPS has a larger conductor cross-sectional area than 1.5mm² TPS.
It is commonly associated with general power and socket-outlet circuits and is one of the cable sizes frequently encountered in residential and light-commercial electrical work.
Typical applications may include:
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General power circuits
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Socket outlets
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Residential fixed wiring
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Selected commercial installations
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Other circuits where 2.5mm² is appropriate for the electrical design
Again, these are examples—not a rule that every socket circuit should use 2.5mm² TPS.
The correct conductor size must be determined from the requirements of the particular installation.
What's the Main Difference Between 1.5mm² and 2.5mm² TPS?
The primary difference is the cross-sectional area of the conductors.
A 2.5mm² conductor contains a greater cross-sectional area of conductive material than a 1.5mm² conductor.
Under equivalent conditions, conductor size affects characteristics including current-carrying capability and resistance.
But this doesn't mean electricians should choose cable based on conductor size alone.
Cable performance is affected by how and where the cable is installed.
Is 2.5mm² TPS Better Than 1.5mm²?
Not necessarily.
Bigger isn't automatically better.
The objective is to select a conductor that is appropriate for the circuit and installation.
Using a larger cable where it isn't required may increase material cost and can make installation more difficult. Using a conductor that isn't adequate for the installation can create much more serious problems.
The appropriate cable is therefore the one that satisfies the requirements of the particular circuit.
Is 1.5mm² TPS Only for Lighting?
1.5mm² TPS is commonly associated with lighting circuits, but describing it simply as "lighting cable" can be misleading.
Cable selection isn't determined solely by whether a circuit supplies lights.
The electrician must assess the actual circuit design and installation conditions.
That includes factors such as:
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Design current
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Installation method
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Cable grouping
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Ambient conditions
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Thermal insulation
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Cable length
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Voltage drop
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Protective device
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Manufacturer information
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Applicable electrical requirements
So while 1.5mm² = lighting can be a useful shorthand in everyday conversation, it isn't a substitute for proper cable selection.
Is 2.5mm² TPS Only for Power Points?
The same principle applies to 2.5mm² TPS.
It is very commonly associated with general power and socket-outlet circuits, but that doesn't mean 2.5mm² is automatically correct for every socket circuit.
Installation conditions can change the cable's allowable current-carrying capacity.
Circuit length and voltage drop may also affect conductor selection.
The actual electrical design determines whether 2.5mm² TPS is appropriate.
Does 2.5mm² TPS Carry More Current Than 1.5mm²?
Under comparable conditions, the larger conductor size generally provides greater current-carrying capability.
However, quoting one universal current rating for "1.5mm² cable" or "2.5mm² cable" can be misleading.
Current-carrying capacity depends on factors beyond conductor cross-sectional area.
For example, the same cable may perform differently depending on how it is installed and the environmental conditions surrounding it.
That's why electricians should use the appropriate cable data and applicable requirements for the installation rather than relying on a generic online amp rating.
How Installation Method Affects Cable Selection
Installation method is an important part of cable sizing because heat needs to dissipate from the conductors.
The thermal environment surrounding a cable can influence its current-carrying capability.
For example, installation conditions involving insulation, grouping with other cables or different ambient temperatures may require different considerations.
This is one reason a cable size that is appropriate for one installation shouldn't automatically be assumed to be appropriate for another.
What About Voltage Drop?
Voltage drop is another important difference to consider when comparing cable sizes.
Electrical conductors have resistance, and voltage decreases along a conductor as current flows through it.
As cable runs become longer, voltage drop can become increasingly important.
In some situations, a larger conductor may therefore be selected even when current-carrying capacity isn't the limiting consideration.
For contractors, this is particularly relevant when dealing with longer cable runs.
1.5mm² vs 2.5mm² for Lighting
For lighting circuits, 1.5mm² TPS is commonly encountered, but that doesn't mean it should automatically be selected for every lighting installation.
The circuit load, installation method, run length, voltage drop and protective device still need to be considered.
There may also be installations where a different conductor size is appropriate.
The circuit should be designed rather than sized solely according to the equipment category.
1.5mm² vs 2.5mm² for Power Circuits
2.5mm² TPS is commonly associated with general power circuits and socket outlets in New Zealand.
However, the same design principles apply.
An electrician should consider:
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Expected circuit load
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Installation method
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Current-carrying capacity
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Cable length
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Voltage drop
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Derating factors
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Protective device
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Manufacturer specifications
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Applicable NZ electrical requirements
If those factors require a different conductor size, the fact that the circuit supplies power points doesn't make 2.5mm² automatically correct.
1.5mm² vs 2.5mm² TPS: Which Should You Choose?
For electrical contractors, the answer comes down to the requirements of the circuit.
As a general reference:
1.5mm² TPS is commonly encountered in lighting and selected fixed-wiring applications.
2.5mm² TPS is commonly encountered in general power and socket-outlet applications.
But the final choice should be based on the electrical design rather than those general associations.
Consider the design current, installation method, derating factors, voltage drop, protective device, cable manufacturer's information and applicable New Zealand electrical requirements before selecting the conductor.
Buy 1.5mm² and 2.5mm² TPS Cable Online in NZ
CoreGrid360 is an Auckland-based online electrical wholesaler supplying electrical contractors throughout New Zealand.
We supply Dominion Cables TPS products, including common cable sizes for residential and commercial electrical work.
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Frequently Asked Questions
What is the difference between 1.5mm² and 2.5mm² cable?
The primary difference is conductor cross-sectional area. 2.5mm² has a larger conductor than 1.5mm², which affects electrical characteristics including resistance and current-carrying capability under comparable conditions. Actual performance depends on the cable and installation conditions.
Is 1.5mm² cable used for lighting in NZ?
1.5mm² TPS is commonly encountered in lighting applications in New Zealand. However, the correct cable size should always be determined from the requirements of the individual circuit.
Is 2.5mm² cable used for power points?
2.5mm² TPS is commonly associated with general power and socket-outlet circuits. This doesn't mean it is automatically suitable for every power circuit.
Can I use 2.5mm² instead of 1.5mm²?
A larger conductor isn't automatically the correct substitution. Cable selection needs to account for the complete circuit design, terminations, equipment, installation conditions and applicable requirements.
Does cable length affect whether I need 1.5mm² or 2.5mm²?
It can. Increasing cable length can increase voltage drop, so circuit length is one factor that may affect conductor selection.
Where can electricians buy 1.5mm² and 2.5mm² TPS cable online in NZ?
CoreGrid360 supplies TPS cable online to electrical contractors throughout New Zealand, with transparent online pricing and project or volume pricing available for larger requirements.
Need More Help Comparing TPS Cable Sizes?
Read our complete TPS Cable Sizes Explained guide for an overview of common 1.0mm², 1.5mm², 2.5mm², 4.0mm² and 6.0mm² TPS cable sizes.
READ: TPS CABLE SIZES EXPLAINED
Or browse the CoreGrid360 TPS cable range to compare available products, specifications and current pricing.
Important Information
This article provides general information for electrical professionals and is not a cable-sizing specification or substitute for electrical design.
Cable selection should be determined for the specific installation by an appropriately qualified person, taking into account manufacturer information and applicable New Zealand legislation, standards and electrical requirements.