October 17, 2026, 11:11 am | Read time: 7 minutes
After a severe thunderstorm, the TV suddenly stops working, the router fails, or the hi-fi system acts up. The question quickly arises: Is the cause in the house’s electrical system, or have lightning and power surges damaged the devices? Dr. Stefan Veit, head of the Electrical and Building Technology division at TÜV SÜD Industrie Service GmbH, explains the connections and how consumers can protect themselves.
The expert’s answer is initially reassuring. Veit does not cite the wiring in the walls as a typical cause of defective devices. Electronics suffer primarily from power surges. Installation defects primarily endanger the residents. Things get dicey in two main cases: The electrical system dates back to before the mid-1970s, or DIY enthusiasts have tinkered with it, such as with outlets, lamps, and wiring. Both can increase the risk of electric shocks and fires.
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Old Doesn’t Automatically Mean Bad
But when is an electrical installation considered “bad”? The term mixes several issues, Veit clarifies. He separates three questions: How is the system equipped? What condition is it in? And how safe is it by today’s technical standards?
Electrical systems age with the house. A system from the 1960s may have been perfectly built at the time. As long as no one changes it, it can usually remain as it is. This is called grandfathering. However, it doesn’t last forever. If danger looms, it’s over.
A major renovation can also void the grandfathering, such as when a basement room is converted into a bathroom. New wiring, switches, and outlets must comply with current regulations, even in older buildings. An old system that is allowed to remain is not automatically safe. It’s similar with cars: A vintage car without airbags is allowed on the road, but it offers less protection in an accident than a new car.
The “airbag” of the electrical installation is the residual current device, or RCD. If electricity flows where it shouldn’t, such as over the metal casing of a faulty hairdryer, it shuts off in a fraction of a second. In many older houses, it is completely or partially missing. It is mandatory for new electrical installations.
Over the years, new outlets, lamps, and wiring are often added to a house or apartment. Such interventions can “significantly degrade the safety level of an originally properly installed system,” warns the expert. This is especially true if amateurs work on the system.
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These Weaknesses Are Common
It’s worth taking a closer look at systems from before the mid-1970s. In West Germany, the classic nulling was allowed until 1973, with a transition period until 1974. Here, a single conductor takes on two tasks. It returns the current and also serves as a protective conductor. Experts call it a PEN conductor. If this conductor breaks or a terminal loosens, the metal casing of a device can become live in the worst case.
In East Germany, such two-conductor systems are sometimes found in newer buildings. Additionally, aluminum wiring is often used there. The material is fundamentally suitable, Veit adds. However, it places higher demands on connections than copper. At aged or oxidized terminals, resistance increases. Thus, the spot can become very hot. Ultimately, the actual condition remains decisive, Veit emphasizes, not just the year of construction.
These Warning Signs Can Be Recognized by Laypeople
Residents can partially assess the condition of their electrical system themselves. The clearest signal: Circuit breakers or RCDs trip repeatedly without an apparent reason. “Such protective devices generally do not react without cause,” explains Veit. Simply resetting them may overlook a fault. Other indications include:
- Scorch marks or discoloration on outlets and switches
- Warm plugs or power strips
- Burning smell
- Flickering lights
- Crackling or buzzing switches
- Devices that only work intermittently
- Loose outlets
- Missing covers
- Damaged cables
Some fuse boxes contain not only the RCD but also an arc fault detection device, or AFDD. It detects dangerous arcs. These are sparks that can occur at damaged wires or poor contacts. If such protective devices trip early, it indicates a high level of protection and potential existing damage, according to Veit. An overly sensitive system is not indicated by this.
Veit also views makeshift solutions with extension cords and power strips critically. If many devices are connected simultaneously, the strip can overheat. However, an inconspicuous electrical system can also have defects, Veit emphasizes. Especially in older houses, after renovations, or after DIY work, a professional inspection provides significantly more safety than a cursory glance.
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Electronics Suffer from Power Surges
And the TV that stays black after the storm? Devices with circuit boards and chips inside are particularly sensitive to power surges. This includes modern household appliances, consumer electronics, computers, power supplies, and smart home components.
Such power surges occur during thunderstorms, due to lightning, or from switching operations in the power grid. Electrical voltage can be compared to water pressure in a pipe. If the pressure suddenly increases, a garden hose can burst. Similarly, electronic components can be damaged or age faster due to a brief power surge.
In older houses, a modern standard surge protection is often missing, according to Veit. The risk to electronics can be higher there. For new buildings, surge protection has been mandatory since the end of 2018. This also applies if new circuits are added in an older house or an electrician updates the installation. If the old electrical system remains unchanged, there is no obligation.
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What an Electrical Contractor Can Do
An electrical contractor can retrofit surge protection in older houses. Can the rest of the system also be improved? “Yes, absolutely,” Veit replies. “Often, relatively simple measures can achieve a significantly higher level of safety and equipment.”
The contractor first assesses the current state. From this, they develop a step-by-step plan: retrofitting RCDs and surge protection, renewing individual circuits or panels, and in extreme cases, modernizing everything. The TÜV SÜD expert emphasizes: “Do not automatically assume a complete renovation.”
- Insulation: Is the plastic sheath of the wires still intact, or has age, damage, or moisture affected it?
- Protective conductor: The green-yellow wire diverts dangerous current from the device casing in case of a fault. The measurement checks if it is continuously connected everywhere.
- Disconnection: Does enough current flow during a short circuit for the fuse to trip quickly enough? Experts call this measurement loop impedance.
- Thermal imaging: A thermal imaging camera shows hot spots in the panel. They indicate loose terminals or overload.
- Currents on protective and neutral conductors: The neutral conductor, usually blue today, returns the current to the panel. Unusual values can indicate so-called “harmonics,” which could lead to overload.
“A single measurement rarely tells the whole story,” Veit summarizes. “Only the combination of visual inspection, testing, and various electrical measurements allows for a reliable assessment of the actual condition of the installation.”
For an apartment, such an inspection often starts at a few hundred euros, according to him. Larger or more complex systems cost more. What exactly is inspected should be clarified in advance with the contractor or an independent expert. Solid technical measurements and clean documentation are crucial, Veit emphasizes.
When It’s Worth Calling an Electrician
These questions help in making the decision:
- Does the system show any of the mentioned warning signs?
- Is the electrical system from before the mid-1970s or from an East German building?
- Are many devices permanently connected to a power strip and running simultaneously?
- Has someone without professional training worked on wiring, outlets, or lamps?
- Are RCDs or surge protection missing in the fuse box?
If you answer several questions with yes or are unsure, it’s best to have the electrical system checked by a professional contractor.