Wiring is hidden inside walls for decades, and undersized wiring is one of the main causes of house fires. Choosing the right wire size for each circuit costs very little extra at construction time and gives a much safer home.
Why wire size matters
Every wire has resistance, so current flowing through it creates heat. Thicker wires have lower resistance and stay cooler. If a thin wire carries a heavy load such as an air conditioner, it heats up, its insulation ages faster, and in the worst case it can melt and start a fire. Learn the physics in our Ohm's law guide.
Common sizes in Indian homes
| Circuit | Typical copper wire size | Typical MCB |
|---|---|---|
| Lighting and fans | 1.0 to 1.5 sq mm | 6 to 10 A |
| General sockets | 2.5 sq mm | 16 A |
| Air conditioner, geyser, oven | 4 sq mm | 16 to 25 A, based on rating |
| Main line from meter to board | 6 to 10 sq mm or more | As per sanctioned load |
These are common practice, not a design. Wire size depends on the load, cable length, how cables are laid and local rules. Always have a licensed electrician size circuits for your home.
Choosing good wire
- Use copper conductors for home wiring.
- Choose FR or FRLS insulation (flame retardant, low smoke), which slows fire spread and reduces toxic smoke.
- Look for the ISI mark and buy from a reputable brand. Counterfeit wire with thinner copper is a real problem.
- Use the standard colours: red, yellow or blue for phases, black for neutral and green for earth.
Good wiring practice
- Give heavy appliances their own dedicated circuits.
- Do not overload a single socket with multi-plug adapters.
- Use separate conduits for power and data or TV cables where possible.
- Protect circuits with the right MCBs and a 30 mA RCCB. See our MCB vs RCCB guide.
- Keep a wiring diagram of where conduits run, so future drilling does not hit a cable.
Frequently asked questions
Is aluminium wire OK inside a house?
Copper is preferred for internal wiring because it conducts better, is more flexible and makes more reliable connections.
How often should house wiring be checked?
Have an electrician inspect older wiring every few years, and immediately if you notice warm switches, burning smells or frequent tripping.