Ask three electricians how much wire a house needs and you will get three answers. That is not because any of them is wrong — it is because the honest answer depends on the layout, and nobody can give you a figure without knowing where the points are going.
What you can do is get close enough to budget properly, and close enough to tell whether a quotation is sensible or padded.
Start with points, not metres
Wire is bought by the coil, but a house is designed in points. A point is anywhere a cable terminates — a light, a fan, a socket, a switch.
A typical two-bedroom house of around 900 square feet works out at roughly:
- 26 light points
- 8 fan and exhaust points
- 12 five-amp sockets for lamps, television and chargers
- 6 sixteen-amp points for the geyser, fridge, washing machine and air conditioner
Around 52 points in total. A three-bedroom house of 1,300 square feet runs closer to 70.
Once you have the point count, the wire follows from it. Each point needs a run from the distribution board and back, and in practice that averages nine to thirteen metres of cable per point depending on the circuit.
Which gauge goes where
This is where people lose money, in both directions — buying heavier cable than the job needs, or buying lighter cable than it should have.
| Circuit | Usual size | | --- | --- | | Light and fan points | 1.5 sq mm | | Five-amp socket circuits | 2.5 sq mm | | Sixteen-amp power points | 4 sq mm | | Mains and sub-mains | 6 sq mm |
There is one important exception, and it catches people out regularly: a long run may need a heavier cable than the load alone suggests. Voltage drops along a cable, and over fifty or sixty metres the drop can be enough that a geyser at the far end of the house never gets the voltage it needs. The fix is a size up, not a bigger breaker.
Our wire gauge selector checks both current capacity and voltage drop, and tells you which of the two is deciding the answer.
A worked example
For that 900 square foot two-bedroom house:
- 1.5 sq mm — around 310 metres, so four coils
- 2.5 sq mm — around 140 metres, so two coils
- 4 sq mm — around 80 metres, so one coil
- 6 sq mm — around 40 metres, so one coil
Plus a twelve-way distribution board, four six-amp MCBs for lighting circuits, two sixteen-amp for socket circuits, three thirty-two-amp for the power points, and an RCCB.
You can run these numbers for your own house with the house wiring estimator.
How to check a quotation
Three things are worth looking at.
Does the point count match the plan? If someone quotes for 40 points on a three-bedroom house, either they have missed rooms or they are planning fewer sockets than you will want.
Is the gauge stated? A quotation that says "wire" without saying 1.5 or 2.5 or 4 is not a quotation you can compare against another one.
Is there an RCCB? It is not optional. It is what protects a person, as opposed to the MCB which protects the cable.
Buy the estimate, not the exact figure
Cable is sold in ninety-metre coils, and part-coils are awkward. Round up to whole coils, and accept that a small amount left over is normal and cheaper than a second trip.
If you want these quantities priced against the brands we stock — KEI, RR, Vishal and Havells — send us the figures and we will quote them properly.