1.5mm² vs 2.5mm² Cable – What’s the Difference and When to Use Each?
Why Choosing the Right Cable Size Matters
Cable size is one of the most important considerations in any electrical installation. In South Africa, using the wrong size can lead to overheating, nuisance tripping, or even fire hazards. It can also result in a failed inspection under SANS 10142, making your installation non-compliant and potentially voiding insurance claims.
Two of the most commonly used fixed wiring sizes are 1.5mm² Surfix and 2.5mm² Surfix. Both are solid-core, rigid cables designed for fixed wiring, but they serve very different purposes.
What is 1.5mm² Cable Used For?
1.5mm² Surfix is generally used for low-current applications where the load is smaller and demand is predictable. Common uses include:
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Domestic and commercial lighting circuits
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Ceiling lights, chandeliers, and LED downlights
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Wall-mounted light switches and control circuits
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Certain low-wattage appliances (only when confirmed by an electrician)
Because lighting circuits typically carry less current, 1.5mm² cable is sufficient when installed correctly.
What is 2.5mm² Cable Used For?
2.5mm² Surfix is a heavier-duty cable designed for higher-current circuits. It is most often used in:
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Plug circuits in homes and offices
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Socket outlets for kettles, fridges, TVs, and computers
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Small appliances and power tools
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Extension of general-purpose outlet circuits
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Moderate fixed appliances (depending on current draw)
By using 2.5mm² cable, these circuits can safely handle higher loads, preventing overheating and ensuring compliance with regulations.
Key Differences Between 1.5mm² and 2.5mm² Cable
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Current capacity: 2.5mm² can handle significantly more current than 1.5mm²
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Applications: 1.5mm² is typically for lighting; 2.5mm² is for plugs and outlets
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Flexibility: Both are solid-core and rigid, but 1.5mm² is easier to route
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Cost: 2.5mm² is slightly more expensive due to its higher copper content
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Compliance: Using the wrong size may result in a failed inspection under SANS 10142
Real-World Examples
Example 1: Lighting Circuit in a House
A typical lounge with 8–10 LED downlights can be safely wired using 1.5mm² Surfix cable on a 10A circuit breaker. Using 2.5mm² in this case would be unnecessary.
Example 2: Plug Circuit in a Kitchen
A kitchen plug circuit feeding appliances such as kettles, toasters, and fridges must use 2.5mm² Surfix with a 20A breaker. Using 1.5mm² here would be dangerous and non-compliant.
Example 3: Long Cable Runs
If lights are far from the DB board, an electrician may upsize to 2.5mm² to reduce voltage drop, even though the load is small.
Which Cable Should You Use?
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For lighting circuits → 1.5mm² Surfix is the standard choice
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For plug circuits → 2.5mm² Surfix is required
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For appliances → Always check the current draw and confirm with a registered electrician
Never substitute one for the other without professional approval. Using the wrong size may result in safety risks and non-compliance with SANS regulations.
Common Mistakes to Avoid
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Using 1.5mm² cable on plug circuits
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Mixing different cable sizes in the same circuit
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Running long distances without accounting for voltage drop
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Oversizing cables without need, adding unnecessary cost
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DIY wiring without a Certificate of Compliance (CoC)
FAQs
Can I use 1.5mm² cable for plugs?
No. Plug circuits require 2.5mm² Surfix for safety and compliance.
Is 2.5mm² cable required for all circuits?
No. 1.5mm² is acceptable for lighting. 2.5mm² is required for plugs.
Which is cheaper, 1.5mm² or 2.5mm²?
1.5mm² is cheaper, but using it incorrectly can lead to costly mistakes and failed inspections.
Does SANS 10142 specify cable sizes?
Yes. SANS 10142 outlines the correct cable sizes for lighting, plugs, and appliances to ensure safety.
Can I mix 1.5mm² and 2.5mm² in one installation?
Not in the same circuit. Each circuit must use one size consistently.
What happens if I use the wrong size cable?
At best, the circuit will trip constantly. At worst, the cable can overheat and cause fire.
Do I need a qualified electrician to install cable?
Yes. Only registered electricians may legally perform electrical work in South Africa.
Buy Surfix Cable Online with Lite-Glo
Lite-Glo stocks a full range of Surfix cable in 1.5mm², 2.5mm², and larger sizes, available by the metre or in full rolls. Whether you are wiring lighting circuits, plug circuits, or appliances, we supply quality cable that complies with South African regulations.
Shop Surfix Cable – Per Meter
Shop Surfix Cable – 100M Rolls
⚠️ Safety & Compliance Notice
All electrical installations in South Africa must comply with SANS 10142-1 (Wiring Code) and the Occupational Health & Safety Act. Work must be carried out by a qualified, registered electrician.
This article is for general educational purposes only. It does not replace professional advice, and Lite-Glo accepts no liability for how this information is used. Always obtain a valid Certificate of Compliance (CoC) for any electrical work.
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