How to tell if your house has aluminium or copper wiring

What to look for in the consumer unit

Open the consumer unit cover and look at where the cables enter the terminals. Aluminium conductors are a dull grey, almost like pencil lead, while copper is a warm reddish-brown, sometimes darkened with age but still recognisably copper-coloured under the terminal screw.

Older Soviet-era units sometimes carry markings on the cable insulation or on a faded label inside the box, occasionally in Russian, giving the conductor size and material as АПВ or АВВГ for aluminium, or ПВС and similar for copper. These labels are not always present or legible, so treat them as a helpful hint rather than proof.

If several cables enter the box and look different from each other, that is worth noting rather than ignoring. Mixed wiring is common in houses that have had partial rewiring over the decades, and it changes what an electrician needs to check when they come out.

Judging cable colour and feel where you can see it

Where cable is visible, such as in an unfinished cellar, loft, or behind a socket you have already removed, look at the colour of the bare conductor rather than the insulation, since insulation colour tells you about the era and standard, not the metal. Aluminium is matte grey and noticeably lighter for its thickness; copper is reddish and feels heavier when you hold a length of it.

Aluminium conductors are also stiffer and tend to hold a bend or show nicks more easily where they have been twisted into a terminal, whereas copper is softer and slightly springs back. A cable that looks unusually thick for the size of the circuit is often a sign of aluminium, since it needs a larger cross-section than copper to carry the same load safely.

None of this is a substitute for testing, but it is enough to form a reasonable expectation before anyone touches a live circuit.

• Grey, matte, stiff conductor: likely aluminium
• Reddish-brown, slightly soft conductor: likely copper
• Unusually thick cable for a small circuit: often aluminium
• Faded markings such as АПВ or АВВГ on old insulation: aluminium
• Mixed colours entering the same consumer unit: possible partial rewiring

Which houses and areas typically have which type

Aluminium wiring turns up most often in Soviet-era panel flats and houses built or rewired from the 1960s through the 1980s, when aluminium was the cheaper, more available conductor. If your building dates from that period and has not been rewired since, aluminium is the safer assumption until you confirm otherwise.

Wooden houses from the 1920s and 1930s, such as those found in Kalamaja or Nõmme, were often wired later than they were built, so the wiring age does not always match the building age. Some have had copper wiring installed during a renovation; others still carry aluminium added decades after the house itself went up.

Newer developments and any house rewired in the last twenty years or so will almost always be copper, since that has been the standard for a long time. A recent renovation history, if you know it, is often a more reliable clue than the building's construction date alone.

What is dangerous and what not to attempt yourself

Aluminium wiring is not automatically hazardous, but it does age differently from copper: the metal oxidises at terminals, connections loosen as the aluminium expands and contracts with heating and cooling, and loose connections generate heat. Warm sockets or switch plates, a persistent smell near a socket, or a breaker that trips for no obvious reason are signs worth taking seriously.

Do not open a live consumer unit beyond the cover, and do not attempt to tighten terminal screws or move cables yourself, particularly on aluminium conductors, which can crack rather than bend. Aluminium behaves differently under a screwdriver than copper does, and a connection that looks fine can fail the next time it heats up.

If you find warning signs, or simply want confirmation of what you have, it is worth booking an electrician to inspect the consumer unit and a sample of the circuits properly. Electrical work of this kind starts from 49 € per hour, and a proper inspection is quick against the cost of guessing wrong.

If the consumer unit itself looks old, is it worth replacing now

An old consumer unit is often the more urgent issue, independent of what the cables turn out to be. Ceramic fuses, missing residual current devices, and scorch marks around terminals are all signs that the board is overdue for attention, whatever metal feeds into it.

Replacing the consumer unit does not automatically mean replacing the wiring behind it, and for a house with sound aluminium wiring and no signs of damage, a new board with correctly rated terminals for aluminium conductors can be a reasonable step on its own. A consumer unit replacement is typically a fixed-price job from 350 €, quoted after an electrician has seen the existing installation or photos of it.

Where the wiring itself shows the warning signs described above, replacing the board without addressing the cables only moves the risk rather than removing it, so it is worth asking for an honest assessment of both together.