If you’ve noticed a strange green substance coming out of your power points or light switches, you’re not alone - and it’s something we do see in older New Zealand homes, including many properties across Christchurch and Canterbury.
While it can look alarming, it’s usually a sign of ageing electrical wiring rather than something you’ve done wrong.
What is the green stuff?
The green residue (often described as “green goo”) is the result of a chemical reaction inside older electrical cables.
It occurs when plasticiser compounds within PVC cable insulation begin to break down over time and react with the copper conductors inside the cable. This reaction produces a green-coloured substance that can sometimes seep out around fittings such as:
Power points
Light switches
Ceiling or wall outlets
In more severe cases, it may even appear as an oily or sticky residue.
Why does it happen?
All PVC electrical cables contain plasticisers to keep the insulation flexible. Over many years, these plasticisers naturally begin to decompose.
When this happens, they react with the copper inside the cable, creating the green discolouration.
This process can be accelerated by:
High temperatures in the cable
Overloaded circuits (too many appliances drawing power)
Loose electrical connections that generate heat
Older or higher-quality cables often include antioxidants designed to slow this breakdown process. However, even these are not immune - given enough time and heat stress, the same degradation can still occur.
Why you may only notice it now
One of the challenges with this issue is that it develops slowly and often out of sight inside walls or fittings.
It can go unnoticed for years until:
A power point or switch is replaced
Electrical work is carried out
Or the residue finally becomes visible externally
We do sometimes see more advanced cases where the substance has built up over time and begins to drip or stain wall areas around fittings.
Is it dangerous?
In short: yes, it can be a serious warning sign as it indicates that the insulation around your wiring is breaking down.
In some cases, this deterioration can contribute to:
Overheating in cables
Increased electrical resistance
Faulty or loose connections
And in extreme cases, electrical fires
This is why it should always be treated as a warning sign, not just a cosmetic issue.
What to do if you see it:
If you notice green residue coming from a power point or switch:
Avoid using the outlet if possible
Do not attempt to clean inside the fitting
Arrange for a registered electrician to inspect the circuit
An inspection will determine whether the issue is isolated or part of wider ageing wiring in the home.
What is the solution?
Depending on what's found, solutions may include:
Replacing affected sections of cable
Repairing or tightening connections
Or, in more extensive cases, partial or full rewiring
In older Christchurch homes, it’s not uncommon to find a mix of original and upgraded wiring, which can increase the likelihood of issues like this appearing.
Where to from here?
Green residue coming from power points is more than just an unusual visual issue - it’s often a sign that electrical wiring has reached the end of its safe lifespan.
If you’re in Christchurch or anywhere in New Zealand and have noticed this in your home, it’s worth having it checked sooner rather than later. Identifying the issue early can help prevent more serious faults and reduce the risk of electrical failure.
Worried about what you're seeing?
Electrical issues like this can worsen over time, so it’s best not to ignore them.
We can take a look, confirm what’s going on, and let you know whether it’s a simple fix or something more serious - no pressure, just clear advice so you know your options.
📞 Call us on 027 406 7414
📨 Or request a free electrical inspection
If you’re in Christchurch or the wider Canterbury area, we’re happy to help.