Why Is My Internet Slow at Night? Causes and Fixes

Why the Time of Day Matters

Most slow-broadband complaints we hear are constant — it’s slow all the time. A slowdown that only appears in the evening is a different animal, and the fact that it’s tied to the clock is the single most useful diagnostic clue you have. Something that changes at roughly the same time every day is almost always driven by demand: yours, your neighbours’, or your household’s. Work through the possibilities below in order and you can usually tell which side of the master socket the problem sits on.

Peak-Time Congestion: The Whole Country Logs On

Between about 8pm and 11pm, most of the UK is streaming, gaming, and video-calling at once. This is peak time, and it strains the network in two places you don’t own.

• Your provider’s local capacity. Everyone on your street or in your postcode shares a slice of your provider’s network. When that slice fills up in the evening, everyone on it slows down together. On older part-fibre (FTTC) connections this is common; on full-fibre it’s much rarer but not impossible.
• The service you’re using. Netflix, YouTube, and the big game platforms also get busier at peak time. A slow evening stream isn’t always your broadband — sometimes it’s the far end.

You cannot fix genuine peak-time congestion yourself; it’s a capacity issue on infrastructure you don’t control. What you can do is prove it, which we cover below, so that when you contact your provider you’re reporting a pattern rather than a vague grumble.

Contention: Sharing More Than You Think

Contention is the industry word for how many households share the same underlying capacity — the “contention ratio”. On a budget package in a densely populated area, a lot of homes may be leaning on the same equipment at once. During the day, when half of them are out, there’s plenty to go round. In the evening, everyone’s home and the shared pipe gets crowded.

This is why two neighbours on different providers can have very different evenings: it depends on how oversubscribed each provider’s local equipment is. If your speed collapses every night at a predictable hour and recovers by bedtime, contention is a prime suspect. Upgrading to a full-fibre or business-grade package with a lower contention ratio is often the real cure — but confirm the pattern first before you pay for it.

Wi-Fi Versus the Line: Test Before You Blame

Here’s the mistake almost everyone makes: they run a speed test on a phone over Wi-Fi, see a low number, and blame their broadband. But your evening slowdown might be your own home network, not the incoming line — and the two need completely different fixes.

To tell them apart, run this simple test during a slow spell:

1. Test over a cable. Plug a laptop directly into the router with an Ethernet cable and run a speed test at speedtest.net or fast.com.
2. Then test over Wi-Fi from the same spot.
3. Compare. If the wired result is good but Wi-Fi is poor, your line is fine and the bottleneck is inside your home — interference, an old router, or too many devices. If both are slow, the problem is the incoming line or your provider’s network.

That one comparison tells you whether to keep reading the Wi-Fi section below or to pick up the phone to your provider.

What You Can Actually Fix Yourself

If the wired test was slow too, the fixable causes are limited — reboot the router, check for a fault on your line, and if the evening pattern is clear, escalate to your provider. But if Wi-Fi was the weak link, plenty is within your control:

• Reboot the router properly. Power it off for 30 seconds, not just a quick restart. Routers that run for months can bog down and an evening reboot often clears it.
• Move to the 5 GHz band. It’s faster and far less congested than 2.4 GHz, which your neighbours’ networks and household gadgets all crowd in the evening.
• Check what’s hogging the connection. A background console update, cloud backup, or someone streaming in 4K upstairs can swallow your whole line at exactly the wrong moment. Pause big downloads during peak hours.
• Cut evening interference. Microwaves, baby monitors, and dozens of nearby networks all peak in the evening. Getting the router central, high, and out in the open helps.
• Consider your router’s age. A cheap or elderly router struggles when 15 devices are all awake at once. A capable router or a tidy network setup copes far better with a busy household.

For a deeper walk-through of the wireless side, our guide on extending Wi-Fi range and killing dead spots in the Support Centre pairs well with this one.

When It’s the ISP — and How to Prove It

If your wired speed is consistently poor every evening and fine every morning, the evidence points at your provider. Build a simple case before you call: run a wired speed test at a slow time and a fast time for a few days and note the numbers and times. Armed with that pattern, ask specifically whether your area is congested at peak or whether a lower-contention or full-fibre package is available. A clear log gets you a far better answer than “it feels slow at night”.

Still Not Sure Where the Slowdown Is?

If you’d rather not spend your evenings running speed tests, we can diagnose it for you — checking whether the bottleneck is your Wi-Fi, your router, or the line itself, and sorting the home-network side properly. Our Wi-Fi setup service covers exactly this across South West London, with remote IT support available UK-wide. Call us on 020 7610 0500, drop into the Putney workshop, or use the contact form and we’ll help you pin it down.