Broadband adverts used to say “up to 76 Mbps”, and a great many customers never got close. The advertising rules changed: headline speeds must now be described as average speeds, measured at peak time, and achievable by at least half of customers.
That is a genuine improvement. It is also widely misunderstood, and the number that actually gives you rights is a different one that never appears in advertising at all.
What the advertised number means
When a provider advertises an average speed, the shorthand is:
> At least 50% of customers on this package achieve at least this speed during peak hours (evenings, typically 8-10pm).
Three consequences people miss:
It is a median, not a promise. Half of customers get less. If you are in that half, the advert is still accurate.
It is measured at the worst time. Peak-time measurement is deliberate and consumer-friendly — it stops providers quoting 3am figures.
It describes the package, not your line. Your specific address, distance from the cabinet and internal wiring determine what you get. On full fibre this variance is small. On copper-based connections it can be enormous.
The number that actually matters: your minimum guaranteed speed
This is the important part.
When you buy, the provider must give you a minimum guaranteed access line speed — a personalised figure for your address, not the package average. It appears in the contract information you are given at sale.
It matters because it carries a right. Under the industry codes of practice, if your speed falls persistently below that guaranteed minimum and the provider cannot fix it within a set period, you can usually exit the contract without penalty — often including any bundled TV or phone service on the same account.
The advertised average gives you no such right. The guaranteed minimum does.
So: when you order, note down the guaranteed minimum you are given. It is the only speed figure with teeth, and most people never look at it.
How to test properly
If you think you are below your guarantee, the evidence has to be right or it will be dismissed — often correctly.
Test over a cable. Ethernet, straight into the router, Wi-Fi turned off on the device. Wi-Fi speed tests measure your home network, which is not the provider’s responsibility. This single point is why most speed complaints fail.
Test several times, at different times of day, including evenings. One bad test proves nothing.
Use more than one testing service. Ofcom offers an official checker; the widely-used independent ones are fine too. Consistency across them is what makes the evidence credible.
Record the results with dates and times. A short log is worth far more than remembered frustration.
Check the router’s own sync speed if you can find it — usually in the router’s admin pages. That is the speed the line itself negotiated, before your home network is involved, and it is the cleanest evidence of a line problem.
Why your speed is lower than advertised
Your Wi-Fi, overwhelmingly the most common answer. If the cabled test is fine and the wireless one is not, no provider action will help you.
Distance from the cabinet, on copper-based connections. This is physics, not fault. Two houses on the same street can differ substantially.
Internal wiring. Old extension cables and poorly-wired sockets cost real speed. Testing at the master socket rather than an extension can be revealing.
Peak-time contention. Shared capacity, worst in the evening. Within limits this is normal and expected.
Your own devices. A five-year-old laptop cannot receive gigabit no matter what arrives at the door.
The line is faulty. Genuinely happens, and it is what the complaint process exists for.
What is not covered
Wi-Fi speeds anywhere in your house. Providers guarantee delivery to the property.
Speeds during your own heavy use. If a large download is running, everything else is slower. That is how bandwidth works.
The advertised average. Being below it is not itself a breach if you are above your personal guaranteed minimum.
The practical takeaway
Three things, and the first two take a minute each:
- At sale, note the minimum guaranteed speed. It is your only enforceable figure.
- Test with a cable before you complain. It is the difference between a complaint that succeeds and one that is dismissed.
- Compare packages on the average speed, but choose on the technology. Full fibre delivers close to its advertised figure consistently, because the physics stops varying with distance. Copper-based connections vary enormously between addresses, so the average tells you much less about what you will get.
That last point is the one worth acting on. A full-fibre 150 Mbps package will very likely deliver something close to 150. A copper-based “average 67 Mbps” package might deliver 70 or might deliver 25, and the advert cannot tell you which.
Sources
- asa.org.uk — Advertising Standards Authority — CAP guidance on broadband speed claims
- ofcom.org.uk — Ofcom — codes of practice on broadband speeds and the right to exit
- ofcom.org.uk — Ofcom — broadband speeds guidance and official checker