Electrical work is priced per point, and a point is a fiction: it is a switch, a socket, a light or a data outlet, and each one is a hole, a back box, a length of cable, a connection and a test. The point count appears on a drawing; the cable, conduit, boxes and labour behind it do not.
That gap is why electrical quotes vary by a factor of two for the same house, and why a takeoff that runs to twenty lines beats one that says "thirty points". This guide explains how to measure cable runs, how much containment each point consumes, and how to build a room-by-room schedule that a contractor can price and an electrician can work to.
Points, circuits and runs
Three different quantities are often conflated:
Points: the outlets, switches and light fittings, counted individually
Circuits: groups of points protected by one breaker, counted per way in the consumer unit
Runs: the cable paths, measured in metres
A point count alone cannot be priced because one socket beside the consumer unit and one socket at the far end of a 20 m garden are the same point and very different work.
Measuring cable runs: three rules
Rule one: measure the path, not the straight line. Cable follows walls, ceilings, joists or conduit, so it takes the right-angled route. A socket on the far wall of a room is not 5 m of cable from the door; it is 5 m plus the height up and down, plus a route around a door frame.
Rule two: add the drops. Every point has a vertical drop from the ceiling or a rise from the floor. A typical drop is 1.5-2.5 m per point, more in a room with a high ceiling or a first-floor outlet.
Rule three: add 10-15% for the tail. Cable is left long at each end for connection and for error, and no electrician pulls a run tight enough to save 200 mm. On a house, this allowance is not optional.
Worked example. A first-floor bedroom with a socket at the far end of a 4.2 m room, fed from a ring final in the ceiling void:
Horizontal route from the ring: 4.2 m plus 1.5 m around a doorway = 5.7 m
Rise from ceiling void to socket height: 2.4 m
Plus a second cable for the ring main, because a ring final is two cables: × 2
Total = (5.7 + 2.4) × 2 = 16.2 m for one socket position
That is the number that makes electrical takeoffs surprising: a single socket can consume 16 m of cable.
Cable sizes and what they serve
Circuit
Typical cable
Notes
|---|---|---|
Lighting
1.5 mm²
Protected at 6 A
Sockets, ring final
2.5 mm²
Protected at 32 A, two cables
Sockets, radial
2.5 or 4 mm²
Shorter runs, fewer points
Cooker
6 mm² or 10 mm²
Depends on rating
Immersion or shower
4 mm² or 6 mm²
High continuous load
Sub-main and outbuilding
6-16 mm²
Voltage drop governs
Cable is sold in 100 m drums for domestic sizes and in cut lengths above that. Ordering whole drums and tracking reserves is how a contractor avoids both shortfalls and a store full of offcuts.
Containment per point
Cable in a domestic building runs in walls and ceiling voids, so containment is minimal. Cable in a commercial or masonry building runs in conduit or trunking, and the quantity per point is substantial.
Working allowances:
Conduit in a masonry wall: 3-5 m per point, plus boxes and couplings
Trunking along a corridor: measured by run length, with drops added
Capping over buried cable: the length of every buried drop
Cable tray in a plant room or roof void: by run length, with supports every 1.5 m
On a brick or block house, capping and conduit for every drop can be 40% of the containment cost, and it is invisible on a drawing.
A room-by-room schedule
The schedule that works has one row per point, with columns for room, type, circuit, cable size and estimated run. Here is a three-bedroom house in outline:
3 sockets, 3 lighting, 3 switches, 1 consumer unit
Two-way switching
Bedroom 1
4 sockets, 1 lighting, 2 switches
Bedroom 2
3 sockets, 1 lighting, 1 switch
Bedroom 3
3 sockets, 1 lighting, 1 switch
Bathroom
1 shaver point, 2 lighting, 2 switches
Zone restrictions apply
Outside
2 sockets, 2 lights, 1 switch
External grade
Total
39 socket outlets, 18 lighting points, 15 switches, plus data
72 points
At an average run of 12-16 m per point including drops and tails, 72 points is 860-1,150 m of cable, which is 9-12 drums of mixed sizes. In practice a house of this size uses about 400 m of 2.5 mm², 200 m of 1.5 mm², and smaller quantities of 4, 6 and 10 mm².
Accessories that follow the points
Back boxes: one per point, plus one per switch position
Grid switches and multi-gang plates: counted as accessories, not as points
Consumer unit: one, with ways counted against circuits plus spare ways
Earth electrode and bonding: measured by run to the water and gas services
Smoke and heat alarms: one per circulation space, interconnected
Data, TV and telephone: separate cable, separate outlets
External fittings: IP-rated, counted separately
The accessories are cheap individually and add up to a meaningful fraction of the material cost.
Circuits and the consumer unit
The number of circuits sets the size of the consumer unit and the amount of cable that has to reach it. A typical three-bedroom house has 10-14 ways: lighting upstairs, lighting downstairs, ring final upstairs, ring final downstairs, kitchen, cooker, immersion, shower, outside, smoke alarms, spare.
Diversity matters: not every circuit runs at full load at once, which is why a house with a 60 A supply can have circuits totalling far more. But the takeoff must still list every circuit, because each one is a cable run to the unit and a way in the board.
Testing, certification and the cost of compliance
Electrical work is inspected and certified, and the testing is not a formality. Continuity, insulation resistance, polarity, earth loop impedance and RCD operation all have to be measured and recorded.
The estimate should carry:
Testing time: 2-4 hours for a domestic installation
Certification: the document and its registration fee
Notification to the local authority, where required
Remedial allowance for the defects that testing finds
A quote that omits testing is not a cheaper quote. It is an incomplete one, and the missing cost appears at the end, when the supply cannot be energised without a certificate.
Labour and productivity
Installing electrical work has two phases with different outputs:
First fix (cable and boxes): 20-35 points per day for one electrician on a new-build domestic property
Second fix (accessories, connections, testing): 15-25 points per day
A 72-point house is therefore 3-4 days of first fix and 3-5 days of second fix, plus testing. Chasing and making good is separate and is usually a builder's cost, not the electrician's.
Productivity drops sharply in occupied buildings, in masonry walls that need chasing, and where the route must avoid existing services.
Waste, drums and the last ten metres
Cable waste is low in percentage terms and high in absolute terms, because drums are large. Allow 5% on cable and 10% on accessories, and keep a reserve drum of the two most-used sizes rather than ordering exactly.
Offcuts shorter than 3 m are rarely usable for a new run and are effectively waste. A well-run job keeps them for alterations and for the odd short drop, which is why an electrician's van has a box of them.
Common errors in electrical takeoffs
Counting points without runs, which prices a house as if every outlet were beside the board
Forgetting the ring is two cables
Ignoring voltage drop on long runs, which forces a larger cable size
Omitting containment in masonry construction
No testing or certification line
Under-counting switches: a two-way stair light is two switch positions and three-core cable
Forgetting external works, which are the longest runs on the job
Chasing, making good and the boundary with other trades
Electrical first fix creates work for other trades, and that work is often missing from both estimates.
Chasing is cutting channels in masonry or blockwork for conduit and boxes. It is dusty, slow work: roughly 0.5-1 hour per metre in blockwork, more in concrete or engineering brick. On a house, chasing can be three to five days for one operative.
Making good is filling the chase, fixing the box, and leaving the wall ready for plaster. If the electrician does not do it, the plasterer charges for it, and neither price includes it if the scope was written loosely.
Coordination matters at ceilings: a downlight conflicts with a joist, a smoke alarm conflicts with a beam. Sorting that at first fix costs an hour; sorting it after plastering costs a repaired ceiling.
The estimating rule is simple: decide who chases and who makes good, and write it into the bill. The most common electrical dispute on a domestic job is not about cable; it is about who fills the channels.
Three-phase, EV charging and the modern load
A house built twenty years ago was designed for a few kilowatts. A house with an electric vehicle charger, a heat pump and an induction hob can draw three or four times that, and the takeoff changes accordingly.
Three-phase supply means a larger consumer unit, more ways, and cables sized for balanced loading.
EV charging needs a dedicated circuit from the board to the parking position, often 10-16 mm² cable over a long external run, plus a protective device and often a data connection for load management.
Load management hardware, whether a current transformer clamp or a smarter device, is an accessory with a price and an installation time.
An electrical estimate for a modern house that assumes the cable sizes and board capacity of a 1990s installation will be short on the largest single run in the building.
Frequently asked questions
How much cable does a house need? A three-bedroom house typically uses 600-900 m of cable across all sizes, depending on layout and whether runs are radial or ring.
How many points per day can an electrician install? 20-35 at first fix, 15-25 at second fix, on new-build domestic work.
How do I estimate cable length per point? Measure the right-angled route plus the drop, double it for ring circuits, then add 10-15% for tails.
Why does the same house get quotes that differ by double? Different point counts, different containment assumptions, and testing or certification excluded from one of them.
Does conduit have to be used? In masonry walls, usually yes for rewires; in timber-frame or ceiling voids, cable can be run unprotected within the permitted zones.
What about data and TV? Separate cable and outlets, priced per point with their own cable type and terminations.
Estimate it with FRELUX
The FRELUX electrical takeoff tool builds a room-by-room schedule, applies run lengths and drops per point, and totals cable by size, back boxes, containment and accessories with costs in your market's currency.