Why Is My Internet Slow? 12 Causes and Fixes for New Zealand Homes

Slow internet in a New Zealand home is rarely the plan. In most cases it is the Wi-Fi, the connection type, or something on the network quietly eating the bandwidth. The causes below are in the order worth checking, from the ones that take a minute to the ones that need a phone call.

First, find out what kind of slow

Run the test above twice: once on a laptop plugged into the modem with a cable, and once over Wi-Fi from the room where the problem is. The gap between those two numbers tells you where to look.

• Wired fast, Wi-Fi slow: the problem is inside the house — causes 1 to 4.
• Both slow, all day: the plan, modem or connection type — causes 5 to 8.
• Fine by day, slow in the evening: congestion — causes 9 and 10.
• Slow and dropping out: a fault — causes 11 and 12, and our guide to connections that keep dropping.

The twelve causes

1. Wi-Fi distance and walls

Signal falls off sharply through concrete, brick, tile and the metal in insulation. A modem in a garage or a cupboard at one end of the house cannot cover the other end. Move it central and high, or add a mesh point — our Wi-Fi extender and mesh guide explains which option suits which house.

2. The 2.4 GHz band

The 2.4 GHz band reaches further but is slow and shared with every neighbour’s network, microwaves and baby monitors. Connect important devices to the 5 GHz band, and if your modem supports the 6 GHz band — opened for Wi-Fi in New Zealand in 2022 and available on Wi-Fi 6E and Wi-Fi 7 gear such as Spark’s 5G Gateway 7 and One NZ’s Deco BE28 — use it for the devices nearest the modem.

3. An old modem

A modem from a plan signed years ago may top out well below your fibre speed, particularly over Wi-Fi. Wi-Fi 5 hardware struggles to deliver more than 200 to 300 Mbps in practice. Providers replace modems cheaply or free on re-contract; ask.

4. Too many devices, one saturating the link

A console downloading an update, a cloud backup, or a laptop syncing photos can take everything the connection has. Check the modem’s device list and pause what you find. Security cameras uploading constantly are a common hidden load.

5. The plan itself

Check what you are paying for. Since June 2025 the old 50/10 Chorus plan is 100/20 and the old 300/100 plan is 500/100 at no extra wholesale cost; if your wired test still shows the old speed, the boost has not been applied. Our guide to what speed you need helps decide whether the plan is actually too small.

6. Copper instead of fibre

The Commerce Commission’s April 2026 measurements put VDSL at 63 Mbps down and 21 Mbps up, and ADSL at 11 Mbps down and 1 Mbps up, against 106 Mbps for the entry fibre plan and 877 Mbps for Fibre Max. Copper is being withdrawn — Chorus now plans to switch it off nationwide by the end of 2028, and only about 44,000 lines remained by mid-2026 — so if fibre is available, moving is the fix, not a faster copper plan.

7. Fixed wireless in the evening

4G fixed wireless averaged 66 Mbps by day and 52 Mbps at peak in the same measurements, with about 48 ms latency. It is shared cell capacity, so it slows when the neighbourhood comes home. Spark’s 5G wireless is much faster, and Starlink now measures 130 to 245 Mbps depending on plan, if fibre is not an option.

8. A 100 Mbps bottleneck in the chain

Older switches, powerline adapters, some TV Ethernet ports and cheap cables cap at 100 Mbps. If a wired test on a Fibre 500 plan shows 94 Mbps, something in the path is Fast Ethernet rather than gigabit.

9. Provider congestion

Fibre itself barely changes at peak — Fibre 500 measured 508 Mbps by day and 506 Mbps at peak. If your wired evening result is far below the daytime one, the constraint is your provider’s capacity. Log the results for a week and raise it; our provider guide covers the complaint path and switching.

10. Malware, adware and browser clutter

A device that is slow while others are fine is usually the device. Malware, crypto-mining scripts, dozens of extensions and a browser with two hundred tabs all show up as “slow internet”. Our malware explainer covers what to look for.

11. DNS delays

If pages take a long time to start loading but then download fast, name lookups are slow. Switching the router to a faster resolver often helps — our guide to changing DNS on a router shows how, and flushing the DNS cache fixes stale entries on a single device.

12. A fault or an outage

A fibre box with a red LOS light, a modem that keeps reconnecting, or a whole street affected at once is a network fault. Check the outage guide for the provider status pages and the Chorus outage map, and the ONT guide for what each light means.

A VPN can be the cause too

A VPN adds encryption overhead and routes traffic through its server. Connected to Auckland the cost is small; connected to Los Angeles it adds around 140 ms and throughput drops with it. If the internet is slow only while the VPN is on, switch to a closer server or a faster protocol such as WireGuard. Our guide to speeding up your connection goes through the rest of the settings worth changing once you know where the bottleneck is.

Frequently asked questions

Why is my internet slow all of a sudden?

Usually a device on the network has started a large download or backup, or the modem needs a restart. Test wired, check the device list, and power-cycle the modem and fibre box before anything else.

Why is my internet slow only at night?

Congestion. On fixed wireless it is the shared cell; on fibre it is more often Wi-Fi interference from neighbours or your provider’s capacity. A wired evening test tells you which.

Why is my Wi-Fi slow but Ethernet fast?

Distance, walls, the 2.4 GHz band or an old modem. Move the modem, use 5 GHz or 6 GHz, or add mesh. More plan speed will not change it.

Will a faster plan fix slow internet?

Only if a wired test already matches your current plan and it is genuinely too small for the household. If the wired test is far below the plan, upgrading pays for speed you still cannot reach.

Does a VPN slow down internet in New Zealand?

A little on a local server, a lot on a distant one. Sydney adds about 30 ms, Los Angeles about 140 ms and London about 265 ms before the VPN’s own overhead.

Is copper broadband slower than fibre?

Much slower: about 63 Mbps for VDSL and 11 Mbps for ADSL against 106 Mbps for entry-level fibre and 877 Mbps for Fibre Max. Copper is being switched off by the end of 2028.