Electrical: lifespan and cost

The electrical system is a safety question as much as an upkeep one. The table shows how long the parts last and what an upgrade usually costs.

The ranges apply to a normal-sized house. Actual cost depends on size, access and region. Lifespan means technical lifespan with normal upkeep.

Component	Lifespan	Replacement cost
Consumer unit	35 yrs (30-40)	30 000-80 000 kr
Electrical wiring	50 yrs (40-60)	100 000-300 000 kr
Sockets and switches	25 yrs (20-30)	10 000-30 000 kr
Residual current device	25 yrs (20-30)	3 000-8 000 kr

When does the wiring need replacing?

Wiring lasts a long time but the insulation grows brittle over the years, and old installations often lack the earthing and residual-current devices required today. A house with its original consumer unit and old fuses rather than circuit breakers is nearing an upgrade. Sockets and switches are cheap to replace as you go; the consumer unit and wiring are the larger item.

What does rewiring cost?

Replacing the consumer unit is a contained job, while rewiring a whole house means opening walls and costs more. A residual-current device is cheap and raises safety the most of anything, and if it is missing it should be the priority. The cost in the table applies to a normal-sized house.

What the age of the house tells you

Some build years carry known risks for exactly these parts. Here are the most common ones.

Asbestos Houses built 1930–1982

Asbestos was widely used during this period. Sampling is required before renovation.

Ungrounded electrical system Houses built 1900–1960

The electrical system from this era almost certainly lacks modern earthing and a residual-current device.

Casein filler in floor levelling Houses built 1977–1983

Casein-based filler gives off ammonia/VOCs when damp. Common in the Million Programme housing during floor renovation.

Must all the wiring be replaced in an older house?

Not always. If the wiring is sound and earthed, updating the consumer unit and adding a residual-current device may be enough. An electrical inspection decides what is needed, and it is cheap relative to the peace of mind.

What is the difference between fuses and circuit breakers?

Fuses are the older technology and are swapped when they blow; circuit breakers reset with a flick. A consumer unit with fuses is a sign the system has some years on it.