Twin & Earth vs Orange Round Cable: Which Do You Need?

By ARCK Electrical · Trade counter, North Parramatta · Reviewed May 2026

Quick Q&A — click to expand

Can I use orange round inside a wall? +

Yes — orange circular is allowed indoors. The catch is cost and dress-out. Orange circular is significantly more expensive per metre than TPS for the same conductor size, and the thicker round sheath is harder to run neatly through framing. Most sparkies break the run at a junction box and switch to TPS once the cable is inside the building.

Is TPS allowed outdoors? +

No — TPS is fixed-building wire, not weather-rated. It's not built for UV, wet conditions, or mechanical abuse outdoors, and AS/NZS 3000 won't accept it in those locations. For outdoor runs use orange circular, and for buried runs use orange circular in conduit (or an XLPE neutral-screen cable for larger feeders).

Do I need to put TPS in conduit underground? +

TPS shouldn't go underground at all, in or out of conduit. Conduit isn't watertight long-term, and TPS isn't rated to sit in a damp environment. For underground runs use orange circular (or an underground-rated equivalent), in marked conduit, at the depth set by AS/NZS 3000 for the install. Cutting corners here is the kind of thing inspectors find years later.

What's V90 insulation? +

V90 is a PVC-insulated cable rated to a maximum continuous conductor temperature of 90°C. Both standard TPS and most orange circular sold in Australia are V90. The 'V' is the PVC; the 90 sets the operating-temperature limit that the AS/NZS 3008 current ratings are calculated against. The cable doesn't normally run at 90°C — that's the upper bound the rating assumes.

Twin & Earth and orange circular both turn up on every residential job, but they're not interchangeable. Pick the wrong one and you either pay too much for a cable that's overspecced, or you pull in a cable that won't pass inspection.

This is the plain version of the difference — what each cable is, where it's allowed to go, and the calls that come over the counter most often.

What Twin & Earth (TPS) actually is

Twin & Earth — TPS, or "flat" — is the flat 2-core-plus-earth cable you'll run in almost every wall, ceiling and indoor conduit in a residential job. The conductors are PVC-insulated, sheathed in a flat outer PVC jacket, and built to AS/NZS 5000.1 as fixed-building wire.

The flat construction is the giveaway. It lies flat against a stud, runs neatly through holes in joists, and clips down without bunching up.

Standard sizes you'll see on a domestic job are 1.0mm², 1.5mm², 2.5mm², 4mm² and 6mm². ARCK stocks all of them in 100m and 500m drums.

TPS is rated V90 — the insulation will sit at 90°C continuously without ageing prematurely. That gives you the current ratings in AS/NZS 3008.1.1.

What orange circular cable is

Orange circular is the round, tougher-sheathed cable you'll see used outdoors, buried, or anywhere a flat cable would get knocked around.

The conductors are insulated the same way as in TPS, but they're laid up in a circular bundle and sheathed in a thicker, brighter-orange PVC jacket. That jacket is the bit that makes the difference: it's thicker, tougher, and built for abrasion and UV.

Most of the orange circular on a domestic site is general-purpose V90 PVC cable built to AS/NZS 5000.1 with a circular outer sheath — still PVC, still V90, just constructed differently to TPS.

For underground runs you'll also see double-insulated orange circular, sometimes with a neutral screen for larger feeders.

Standard sizes are the same as TPS — 1.5mm², 2.5mm², 4mm², 6mm², 10mm², 16mm², 25mm² and up — with the larger sizes more common on sub-mains and outdoor feeders.

Where each one goes

Here's the call most sparkies make in their head every time they uncoil a drum:

Use TPS for:

• Lighting circuits inside the building
• General-purpose 16–20A GPO circuits inside the building
• Fixed wiring runs in conduits, partitions, ceilings and chases — protected by the building structure

Use orange circular for:

• Outdoor runs (eaves, soffits, exterior surface-mounted)
• Underground runs in conduit (sub-mains to garages, granny flats, sheds)
• Garden lighting and pool/spa supply cables
• Any run where the cable is exposed to weather, knocks, or UV

The dividing line is whether the cable is protected by the building or whether it has to look after itself in the open.

What about TPS in a conduit underground?

You'll occasionally see TPS dropped into conduit and buried as a shortcut. AS/NZS 3000 isn't on board with that for most residential installations.

Underground conduit is a wet environment, joints and saddles fail, and TPS isn't rated to live in damp or buried conditions long-term.

The correct cable for an underground sub-main is orange circular (or an XLPE neutral-screen cable for larger jobs), in a marked, protected conduit, at the depth specified in AS/NZS 3000.

What about orange circular inside a wall?

The other direction — running orange circular indoors — is allowed and sometimes done for runs that pass through both indoor and outdoor sections without a join.

The catch is cost: orange circular is significantly more expensive per metre than TPS for the same conductor size, and a thick round jacket is harder to dress neatly in a wall cavity. Most sparkies break the run at a junction box and use TPS for the indoor leg.

Sizing — same current tables apply

Current capacity is set by the conductor size and the installation method, not by whether the sheath is flat or round. A 2.5mm² Cu conductor in TPS and the same 2.5mm² Cu in orange circular carry the same load when installed in comparable conditions.

The installation methods that matter (per AS/NZS 3008.1.1) include:

• In free air — clipped to a surface, well ventilated
• Enclosed in a wall — typical TPS install
• In conduit, enclosed — typical for both TPS and orange circular
• Buried, direct — orange circular only (or rated equivalents)
• Buried in conduit — orange circular standard

Each method gives a different current rating because the cable runs hotter or cooler depending on how much heat it can shed. Bundling and ambient temperature derate the rating further.

If you'd usually run 2.5mm² TPS for a 20A GPO circuit indoors, you'd use 2.5mm² orange circular for the same circuit outdoors — same conductor, same protection, different sheath.

See our cable sizing chart for the full set of typical residential combinations.

What's V90?

V90 is the cable rating you'll see stamped on the sheath of both standard TPS and most orange circular. The "V" refers to the PVC insulation; the 90 is the maximum conductor operating temperature in degrees Celsius.

A V90 cable can sit indefinitely at 90°C at the conductor without the insulation degrading early. That doesn't mean it runs at 90°C — it means the current rating in AS/NZS 3008 is calculated on the basis that the conductor will reach but not exceed that limit.

You'll occasionally see higher-rated cables (e.g. XLPE-insulated cables with better short-time fault rating) on larger sub-mains or solar runs.

Pricing — the short version

Per metre, at trade prices:

• TPS — cheapest of the two. The flat construction uses less sheath material.
• Orange circular — usually 30–60% more per metre for the same conductor size, depending on the size.

That price difference is the main reason to use TPS indoors when you can. Run a 100m sub-main outdoors in orange circular and the cost difference adds up; doing the same run in TPS would save money but won't pass inspection.

Order from ARCK

We carry the full range of both TPS and orange circular at our North Parramatta trade counter — 100m and 500m drums of every common size, same-day pick-up if you call before lunch. Need orange circular for an outdoor sub-main or a buried garden-lighting run?

We've usually got 4mm, 6mm and 10mm on the floor. Browse the full cable range, or call the counter on (02) 9890 9693 for stock checks.

Mon–Fri 6:30am–5pm, Sat 7:30am–1pm. If you're not sure which to use, ask.

We talk through these calls every day and we'd rather you walk out with the right cable than have to come back for it.