Why Are My Lights Flickering? A Scottish Electrician's Guide to What It Actually Means

There’s a particular pattern to how a flickering light starts. It’s fine for months. Then one evening, watching the telly, you catch the lamp in the corner doing a barely-perceptible shimmer. You blink. It does it again. Now you can’t unsee it.

What follows is usually a few weeks of “I’ll deal with that later”, then either the bulb dies and you forget the whole thing, or it gets noticeably worse and you finally pull out your phone to find out whether you need an electrician or whether you’re being neurotic.

Both are valid endings. Here’s how to tell which one you’re heading for — ranked roughly from “change the bulb” to “stop reading this and switch the circuit off.”

1. The bulb is on its way out (60% of cases)

This is almost always it. Modern LED bulbs are rated for 15,000-25,000 hours but the cheap ones from supermarket multi-packs frequently die at a fraction of that — and they often die slowly, flickering for weeks before they pack in entirely.

The test: swap in a known-good bulb from another fitting. If the flicker stops, you’ve found it.

A few subtleties that catch people out:

• Dimmable circuit + non-dimmable LED = flicker. The packaging will tell you.
• Mixing LED brands in the same multi-bulb fitting can cause flicker because they don’t share the same drive characteristics.
• Smart bulbs (Hue, Smartthings, etc.) flicker briefly when the network drops. Five-second flicker every now and then is normal; sustained flicker isn’t.

2. Loose bulb in the socket (15%)

Bayonet fittings — the standard UK twist-lock — lose their grip after the bulb has been in and out a few times. Especially in ceiling roses where the spring tension flattens over the years.

Turn the light off at the switch, give the bulb a gentle quarter-turn anticlockwise then clockwise back in, and try again. If you’ve got an Edison-screw fitting (E27, common on lamps), screw it in a touch more firmly.

If a fitting feels loose around the bulb itself — like the holder is wobbling — that’s a fitting problem, not a bulb problem. See cause 4.

3. Faulty wall switch (10%)

Switches don’t last forever. The internal contacts arc every time you flip them, and over twenty years of being switched 30 times a day, they pit and corrode. The result is intermittent connection — which shows up as flicker.

Tell-tale: only one light flickers, the bulb’s already been swapped, the rest of the circuit’s fine, and the flicker often happens shortly after the switch is flipped on rather than continuously.

Replacing a wall switch is not something I’d encourage a homeowner to do themselves, even though plenty of YouTube videos make it look straightforward. Since 2007, replacing accessories on existing circuits has been notifiable work under Scottish Building Regulations if it’s in a “special location” (bathrooms, near sinks etc.), and Part P of the regs assumes a registered electrician is doing it elsewhere too.

Realistic price: a SELECT or NICEIC electrician will charge £60–£120 for a one-trip switch replacement, including a basic switch. Higher if it’s a smart switch or you want it moved.

4. Loose connection somewhere in the circuit (8%)

This is the one that matters. A weak connection — at a ceiling rose, in a junction box, at the back of a switch plate, in a socket — causes intermittent contact. Intermittent contact at mains voltage causes arcing. Arcing causes heat. Heat in confined spaces near wood, dust, and insulation is how electrical fires start.

You’ll usually have at least one of these warning signs before it becomes dangerous:

• The flicker gets noticeably worse when another appliance on the same circuit kicks in (kettle, washing machine, shower)
• A switch plate, socket, or light fitting feels warm to the touch when the light’s been on a while
• A faint smell of hot plastic or — and this is the bad one — burning, near a fitting
• The flicker accelerates suddenly after weeks of being steady

If any of those apply: turn off the circuit at the consumer unit. Do not keep using the light. Call a registered electrician. This is the failure mode that fire investigators see most often in domestic electrical fires.

Cost to fix is usually small — £80–£150 for an electrician to find and repair the loose connection on a single visit — which is what makes it tragic when people put off the call until something goes wrong.

5. Voltage drop from a big appliance (4%)

If your lights dim or flicker noticeably every time a large appliance starts up — washing machine motor, electric shower, kettle, oven element — you’re seeing voltage drop, not a fault in the lighting circuit.

Old Scottish housing makes this surprisingly common:

• Tenement flats with shared rising mains sometimes show voltage dips when a flat upstairs draws hard.
• Rural properties on long single-phase service cables see dips when bigger loads start.
• Outbuildings on a sub-main off the main consumer unit will dim noticeably when something heavy starts.

Within a small range (a brief dim when the shower starts) it’s normal. If the lights are dropping noticeably for more than half a second, or if they’re flickering visibly during the appliance’s whole run, your supply quality is poor enough to investigate. Ring your DNO (SP Energy Networks for central/southern Scotland, SSEN for the north and islands) — they’ll come and measure your supply free of charge.

6. Consumer unit problem (2%)

If the flickering affects multiple rooms across more than one circuit, the problem isn’t downstream — it’s at the source. The most common cause is a worn MCB (miniature circuit breaker) that’s developing a high-resistance fault internally. The next most common is a loose neutral connection in the consumer unit itself.

Anything pre-2008 has a wired fuse box, not modern MCBs, and is candidates for an upgrade anyway. Anything pre-2018 was probably installed before the 18th Edition wiring regs came in and may not have the dual-RCD protection that newer units do. If you’re seeing multi-circuit flicker and your CU is old, it’s a good prompt to get the unit checked.

Cost expectations:

Job	Typical Scottish price
Replace a single MCB	£80–£120
Tighten loose neutral, full CU check	£100–£180
Full consumer unit upgrade (4–8 way)	£450–£800
Full CU upgrade plus EICR	£550–£950

The EICR (Electrical Installation Condition Report) is a full safety check of the whole house’s wiring. If you’ve never had one and the house is over 20 years old, it’s £150–£250 well spent.

7. Grid event (1%)

If everything in the house flickers briefly at the same moment, multiple times an evening, and your neighbours are seeing it too — that’s the grid, not you. Storms, substation switching, and tree contact on overhead lines all cause brief voltage dips that show up as light flicker.

Report it to your DNO. They keep a log of these events per area and will investigate persistent ones. Calling an electrician won’t help — they’ll arrive, the supply will be steady, and you’ll have spent £80 confirming what your neighbours could’ve told you for free.

Quick reference: who to call, when

Symptom	Likely cause	First action
One bulb flickers, fitting feels normal	Bulb dying	Swap it
One light flickers, new bulb’s fine	Switch or wiring	Electrician
Multiple lights, one circuit	MCB or junction	Electrician
All lights, briefly, when kettle starts	Voltage drop	Probably fine — log it
All lights, multiple times an evening	Grid event	Check neighbours, call DNO
Warm switch plate, faint burning smell	Loose connection — fire risk	Off at CU. Electrician now.

A note on “any electrician”

In Scotland, three certification bodies cover domestic electrical work: SELECT (the long-standing Scottish body), NICEIC (UK-wide, very common), and NAPIT. All three are equally valid for residential work. What matters is that the person doing the job is registered with one of them, not which one.

If they’re not registered with any of those? Walk. Domestic electrical work by an uncertified person isn’t just risky — your insurance won’t cover anything that goes wrong, and if you ever sell the house, the buyer’s solicitor will flag the lack of certificates.

Top Scot Trades lists the highest-rated registered electricians in every major Scottish city, ranked by real customer reviews — browse them by city here if you’d rather not start with Google.