The question of backup internet almost always arrives late, the day after the incident that made it feel necessary.

And the answer isn't "yes, every business needs one". Plenty of businesses genuinely don't, and buying them a backup means paying every month for a problem they don't have.

Do the maths before you shop

The only figure that decides is what an hour of downtime costs you. That number varies enormously between businesses of identical size.

Stops entirely when the internet goes:

  • Tills that depend on cloud-based systems.
  • Businesses where all payment is digital.
  • Services whose orders arrive through an app.
  • Clinics and practices with online records, see the guide to internet for clinics.

Only partly disrupted:

  • Businesses still taking cash, with a standalone card machine.
  • Cafés where guest Wi-Fi is a nicety rather than a requirement for trading.
  • Offices where most work can wait a few hours.

The comparison is honest and quick. If a single hour of loss already exceeds a month of backup cost, the decision is made. If a two-hour outage once a year merely delays some work, the money does more good elsewhere.

The condition people skip: the path must differ

This is the most expensive mistake in backup internet, and it always takes the same shape, two subscriptions from two different providers that turn out to run down the same cable.

In many places, different providers lease the same physical network, or at minimum share poles and ducts to the same exchange. When the cause is a cable cut by digging, or an area fault, both go dark together, and you've paid twice for one point of failure.

So the question isn't "which provider is different" but "which path is different":

  • Fibre primary, cellular backup. The most common pairing, for good reason: the two are genuinely separate from the cable all the way to the tower.
  • Fibre primary, another provider's fibre as backup. Only meaningful once you've confirmed the runs enter from different directions. Worth asking before you sign.
  • Cellular primary, a second operator as backup. Sensible where there's no fibre, provided the two operators' towers aren't on the same mast.
  • Satellite as backup. For remote sites with no alternative, see the guide to satellite internet.

Building the backup

Simplest: a phone hotspot

A spare phone with a data SIM, switched on when needed. It costs almost nothing, and for a single till it's often enough. The method is in the guide to creating a hotspot, and the usual snags are covered in the guide to phone hotspot connection problems.

Its limits are plain: someone has to switch it on, and every device must be moved across individually. Beyond a handful of devices that becomes tiring at exactly the wrong moment.

Middle ground: a 4G router using the same SSID

A dedicated cellular router, configured with exactly the same network name and password as the primary network, but left switched off.

When the primary line fails, the main router goes off and the backup comes on. Because the name and password match, every device reconnects by itself, untouched, and that is what makes this markedly better than a phone hotspot. Device selection is covered in the guide to choosing a MiFi or 4G router.

Tidiest: a dual WAN router

A router with two WAN ports watches the primary line and moves across by itself when it stops answering. The switch takes anywhere from a few seconds to about a minute, depending on configuration.

This is the right choice when your business genuinely halts without internet. Two things to check before buying: whether the second WAN port accepts a USB modem or only a cable, and whether the failover can be tested without unplugging anything.

Not everything should move across

A backup path is nearly always slower and metered. Moving the whole network onto it will exhaust it within hours, often on things that weren't urgent at all.

Set the order before the incident:

  1. Must work: till, payment terminals, office phones.
  2. Should work: email, customer messages, incoming orders.
  3. Can wait: guest Wi-Fi, backup uploads, device updates.
  4. Must stop: video playback, large cloud syncing.

The easiest way to enforce that order is to switch guest Wi-Fi off while the backup is active, or throttle it hard, see the guide to limiting Wi-Fi speed. If the guest network is already separated as in the guide to separating guest networks, that's a single switch.

Backup internet without backup power is half a plan

Most internet outages coincide with power cuts. A backup router that dies alongside the mains solves nothing.

One small UPS powering the router and switch covers most incidents, and costs far less than people expect. The details are in the guide to a UPS for your router.

If your devices are spread out and powered over the network cable, a single UPS in the rack can keep all of them alive at once, see the guide to PoE.

An untested backup isn't a backup

This is the most-skipped part, and the one that decides everything.

A data SIM never used may well have expired. A backup router stored for a year may have a password nobody remembers. Automatic failover that has never been tried may simply never have worked since the day it was installed.

A drill once a quarter is enough, and it needn't take long:

  • Disconnect the primary line during a quiet hour.
  • Time how long until everything is working again.
  • Confirm the till and payment terminals can genuinely complete one transaction.
  • Reconnect the primary line, and confirm the system returns to it.

That last step is the one people forget. A network that stays on the backup after the primary recovers will quietly consume the month's data allowance by the end of the week.

Write the steps down; don't keep them in your head

One sheet taped near the router: the order of steps, the network names, and the numbers to call. Whoever is on duty when it happens is often not you, and that person needs to be able to do it without phoning anyone.

Start from the cost per hour, not from the hardware. If that number is small, a backup isn't worth it, and there's no need to feel careless about skipping it.

If it's large, one condition outweighs every other consideration: the backup path must be genuinely separate from the primary. Two subscriptions down the same cable aren't a backup, just a second bill.

And whatever you install, test it quarterly. A backup that has never been switched on is a promise, not protection.

Frequently asked questions

Does every business need backup internet?

No. What decides isn't the size of the business but whether it stops when the internet does. A till that only takes digital payment stops entirely; a shop taking cash doesn't. Work out the loss per hour first, then compare it against the monthly cost of a backup.

What's the cheapest sensible backup?

For most small businesses, a data SIM in a 4G router, or even a hotspot from a spare phone, covers the majority of incidents. What matters isn't its speed but that it runs on a genuinely different path from the primary line.

Why are two fibre lines at one address often pointless?

Because they frequently follow the same cable and the same poles to the same exchange. When the cause is a cut cable or an area fault, both fail together. A backup only means something if its path is actually different.