Why your broadband sags at 9pm and nobody can explain it
Your speed test says 100Mbps. Your Netflix says otherwise, right around the time everyone else on your street sits down for the evening too. That’s usually not a fault on your line. It’s contention, and it’s the part of broadband nobody tells you about when you sign up.
Providers sell you a headline speed. What they don’t put on the box is that you’re sharing capacity back to the exchange or cabinet with your neighbours, and contention ratio is simply a measure of how many neighbours you’re sharing it with.
What is contention ratio?
Contention ratio is the number of homes sharing the same chunk of network capacity. It’s a term that comes from the older copper broadband era, where a typical residential connection was quoted at around 50:1, meaning up to 50 properties could be drawing on the same backhaul link at once, against roughly 20:1 for a business line. That’s why business broadband has always cost more for the same headline speed.
On modern full fibre networks providers rarely publish a fixed ratio at all, because capacity is managed dynamically rather than carved up in fixed blocks. The principle still holds though: you are sharing, and the more people using their share at once, the less there is to go round.
Why does it get worse in the evening?
Ofcom’s own performance monitoring tracks exactly this pattern. It found download speeds during peak hours of 8pm to 10pm were 5% slower than average maximum speeds, with speeds at their lowest between 9pm and 9.59pm across every broadband technology, and at their highest between midnight and 5.59am (checked September 2026).
Two things worth taking from that. The effect is real and it is measurable. It is also, on average, a 5% dip rather than the collapse it can feel like, so if your connection becomes genuinely unusable every evening, contention alone probably isn’t the whole story and it’s worth raising a fault.
It’s the broadband equivalent of a motorway. Plenty of lanes at 3am, busier at half past six, but still moving.
Key takeaways
- Contention ratio measures how many homes share the same network capacity, quoted at around 50:1 on older residential lines.
- Ofcom measures peak hour speeds at 8pm to 10pm as about 5% below average maximum speeds, with the low point between 9pm and 10pm.
- A 5% average dip is normal. A connection that becomes unusable every evening is worth reporting as a fault.
- Full fibre reduces the impact of contention because there’s simply more capacity to share.
- A speed test at midday tells you nothing about what you’ll actually get at 9pm.
Does full fibre fix contention?
Not entirely, but it helps a lot. Full fibre networks carry far more capacity than the old copper based lines, so the same number of shared users has more room to breathe. A shared slice of a gigabit connection still leaves plenty for everyone at peak time. A shared slice of an ageing copper line doesn’t.
This is also where router placement and home wifi setup get unfairly blamed. If your broadband is slow specifically in the evening and fine at 2pm, contention is a more likely culprit than a router stuck behind the telly.
How providers actually manage contention
Providers don’t just leave contention to chance. Most use traffic management, sometimes called network shaping, to keep things fair when a shared link gets busy. Video streaming might get gently deprioritised for a few seconds behind, say, someone on a work call, all without you noticing.
The catch is that traffic management smooths things over rather than solving contention outright. It stops one household hogging the whole cabinet, but it can’t manufacture capacity that isn’t there.
This is also why two people on the same street, same provider, same package, can report different experiences. One might sit on a cabinet serving a handful of homes, another on one serving far more. Contention is rarely uniform even within a single postcode, whatever the marketing suggests.
Three checks before you blame your router
- Test at different times. Run a wired speed test at 2pm and again at 9pm. A gap points to contention rather than your home network.
- Compare the size of the gap. Ofcom’s benchmark is about 5% at peak. Losing half your speed every evening is a different problem and worth raising with your provider.
- Consider full fibre if it’s available. Where you can get it, a full fibre connection makes evening contention far less noticeable than a part fibre or copper line ever manages.
None of this means you’re being ripped off. It’s just how shared infrastructure works, and providers rarely explain it because “you’re sharing capacity with your neighbours” doesn’t fit on a billboard. Roo’s view: it’s less a scandal, more a fact of life, like a busy motorway junction nobody built big enough for rush hour.
Frequently asked questions about contention ratio
- Can I ask my provider what my contention ratio is?
- You can ask, but most residential providers don’t publish an exact figure per address, and on full fibre networks a fixed ratio often doesn’t exist in the old sense. Business and leased line packages are more likely to state one explicitly, since customers pay extra for it.
- Is a lower contention ratio always better?
- Generally yes, since fewer homes are sharing the same capacity. It’s one reason business connections cost more for the same advertised speed as a residential one.
- How much slowdown is normal in the evening?
- Ofcom measures average peak hour download speeds at around 5% below average maximum speeds between 8pm and 10pm. Substantially more than that, consistently, is worth reporting.
- Does contention affect gaming more than streaming?
- Congestion tends to hit latency as well as raw speed, which matters more for real time gaming than for streaming, where a bit of buffering is less noticeable.
- Will switching provider fix an evening slowdown?
- Sometimes. If your current line is older copper based infrastructure, switching to a full fibre provider in your area often helps more than switching between two similar copper packages.
- Is contention ratio the same as a data cap?
- No. A data cap limits how much you can download in total. Contention is about how many people share the pipe at the same moment, regardless of any cap.
If evenings are consistently the problem, it’s worth checking what’s actually available on your street rather than assuming every provider will behave the same way. And if you’re paying full price for a package that struggles every evening, it’s also worth a quick look at whether your current bill still matches what you’re getting.
Contention isn’t a fault you can fix with a router reboot. But once you know it exists, and roughly how big the effect should be, at least the 9pm buffering wheel stops feeling personal.
Sources
Checked September 2026.
