Does my internet still work in a power cut?

No. Your router needs mains electricity, so it goes off the moment the power does, even though the fibre or phone line outside is usually unaffected. This catches people out because they assume a broadband fault and a power cut are separate problems. A battery-powered MiFi keeps working, which is why it is the most useful backup for a power cut specifically.

How much mobile data do I need for a broadband backup?

For email, documents and messaging, 5GB covers a long outage comfortably. Video calls are the expensive part at roughly 0.5 to 1.5GB per hour, so a day of meetings can use 10GB on its own. Buy a data-only SIM with a long expiry rather than a monthly plan, since a backup line sits idle most of the time.

Can I just use my phone as a hotspot instead?

Yes, and you should try it first because it is free. The limits show up over a longer outage: it drains the battery fast, ties up the phone you need for calls, and many contracts cap or throttle tethering. It is the right answer for a thirty-minute blip and the wrong one for a working day.

Should my backup SIM be on a different network to my broadband?

It should be on a different network to your phone, and ideally not one that piggybacks the same infrastructure. Many budget providers resell EE, O2, Vodafone or Three coverage, so two SIMs from different brands can share one mast. Check whose network a provider actually uses before assuming you have redundancy.

Is 5G worth paying for on a backup connection?

Usually not. A backup line needs to be reliable, not fast, and 4G already carries video calls comfortably. 5G coverage is also patchier, so a 5G device may fall back to 4G at your address anyway. Spend the money on checking coverage and on a device with external antenna ports instead.

Buying guide

Staying online when the broadband dies.

An outage costs you calls, card payments and a day's work. Keeping a backup is cheaper and simpler than most people expect, and there is one thing about it that almost everybody gets wrong.

The thing people get wrong

In a power cut, your internet goes off too.

The fibre or phone line outside your house is usually fine during a power cut. Your router is not, because it runs on mains electricity. So does the street cabinet in some cases. People treat "power cut" and "broadband fault" as two separate problems and are then surprised to be offline.

This matters when choosing a backup, because it rules out anything that also needs a plug. A mains-powered 4G router is a fine answer to a line fault and no answer at all to a power cut. A battery-powered MiFi covers both, and that single fact is why it is usually the right first purchase.

Line fault: your kit is fine, the connection is not. Any 4G option works.
Power cut: your router is dead. Only battery kit helps.
Provider outage: regional or national. You need a different network, not different hardware.
Moving house: a gap of days or weeks between activation dates.
Laptops have batteries. Desktops, VoIP phones and card terminals do not.

Option 1

Tether your phone

Free, already in your pocket, and the right first move. Turn on the personal hotspot and you are working again in thirty seconds. Try this before spending anything, because for a short blip it is genuinely all you need.

It falls apart over a longer outage. It flattens the phone you also need for calls, it is fiddly to share with a household, and plenty of contracts still cap or throttle tethering even on "unlimited" plans. Worth checking your own terms now rather than discovering it mid-outage.

Free and immediate.
Fine for a short outage or a single laptop.
Heavy battery drain on the phone you need.
Tethering caps are common, even on unlimited plans.
Awkward for desktops, printers and anything without Wi-Fi.

Option 2

A MiFi with its own data SIM

A pocket device with a battery and a SIM slot that makes its own Wi-Fi network. This is the sweet spot for most homes and small offices: it keeps working in a power cut, everyone connects to it at once, and it leaves your phone alone.

Because it is a separate SIM, you can put it on a different network to your phone, which is what gives you real redundancy rather than the illusion of it. Keep it charged and in a drawer, and it is a genuine insurance policy for the price of a takeaway.

Battery powered, so it survives a power cut.
Shares one SIM across the whole household or office.
Can sit on a different network to your phone.
Needs its SIM kept in credit, or it is a paperweight when you need it.
Reception depends on where you put it, so near a window beats in a cupboard.

Option 3

A mains-powered 4G or 5G router

A step up in performance and a step down in power-cut resilience. These have better aerials than a pocket device, often take external antennas for a weak-signal site, and give you Ethernet ports for kit that has no Wi-Fi.

The right pick when the backup has to serve a whole office, run a VoIP phone system, or sit permanently in a spot with marginal signal where an external aerial on the wall makes the difference. Pair it with a small UPS and you have covered power cuts too.

Better antennas, and external aerial ports on many models.
Ethernet ports for desktops, phones and card terminals.
Handles more devices than a pocket MiFi.
Dies in a power cut unless you add a UPS.
Not portable, so no use in a van or caravan.

Option 4

A second fixed line, or automatic failover

The proper business answer. A dual-WAN router watches your main connection and switches to a second one within seconds when it drops, so calls survive and nobody notices. The second line can be another broadband service or a 4G modem.

Worth it when downtime genuinely costs money: a shop that cannot take card payments, a practice that cannot access records, a team whose phones are VoIP. If you go this route, make sure the backup uses different infrastructure, or a single street-level fault takes out both.

Switches over automatically, often without dropping calls.
The only option that protects unattended systems.
Most expensive, and needs configuring properly.
Pointless if both lines share the same cabinet or duct.
This is the tier where it is worth getting help rather than guessing.

Do this before you buy

Check coverage at your address, not your town.

Mobile coverage varies street by street, and a network that is excellent in the town centre can be unusable at your back door. Check your actual postcode on the network's own coverage map, and on Ofcom's independent checker, before you commit to a SIM. Then pick a network that is not the one your phone already uses, so a single network outage cannot take out both.

One catch worth knowing: a lot of budget SIM providers resell coverage from EE, O2, Vodafone or Three. Two different brands can quietly sit on the same mast, which is no redundancy at all. Check whose network you are actually buying before you assume you are covered.

Data and SIMs

Buy a long-expiry data SIM, not a monthly plan.

A backup line sits unused for months, so a rolling monthly contract mostly buys you nothing. Data-only SIMs sold as multi-month or annual bundles suit this far better: load it once, leave it in the drawer, and it is still valid when you need it.

Rough figures so you can size it. Email, documents and messaging barely register. Video calls are what eat data, at roughly 0.5 to 1.5GB an hour depending on quality, so a full day of meetings can burn 10GB by itself.

5GB: comfortable for a long outage of email and documents.
20GB: a few days including video calls.
50GB+: only if this is a working second line, not insurance.
Set a calendar reminder for the SIM expiry date. A dead SIM is the most common reason a backup fails.
Test it once a quarter. Untested backups are not backups.

Quick answer

Which one do you need?

Work from home, occasional outages: a MiFi with a long-expiry data SIM.
Calls you cannot afford to drop: 4G router plus a UPS, or proper dual-WAN failover.
Shop taking card payments: automatic failover. Manual switchover is too slow at a till.
Caravan, motorhome or site office: a MiFi, since it is the only portable option.
Gap between house moves: a MiFi and a one-month data bundle.
Frequent long power cuts: battery kit only, and charge it before the storm arrives.

Recommendations

Disclosure: the product links below are Amazon affiliate links. If you buy through one, LMC Tech earns a small commission at no extra cost to you. A commission never buys a place on this page, and we say plainly which hardware we have used ourselves and which we have not.

Tested by us

What we actually keep for outages.

We standardise on TP-Link for customer installs because the firmware gets updated, the apps are not hostile and spares are easy to get years later. That is a deliberate preference rather than the result of a brand shootout.

Portable 4G MiFi: TP-Link M7350 Cat4 portable 4G MiFi — What we actually keep in the van and hand to clients during an outage. Takes any data SIM, shares it with up to ten devices, and the screen tells you signal strength, which matters more than any spec when you are hunting for a bar of reception.
Watch out: Cat4 tops out near 150Mbps and real speed depends entirely on local 4G, so check coverage at your postcode first. Around 8 hours of battery, and it is a stopgap for a dead line rather than a second broadband service.

Related guide

Is it really an outage, or just poor Wi-Fi?

If the connection is not dead but merely awful in certain rooms, a backup line will not help. That is a coverage problem, and it has a different set of answers.

Read the Wi-Fi coverage guide

Want it set up properly?

We fit failover for businesses that cannot afford to drop offline.

We can work out which network actually performs at your address, size the data sensibly, and configure automatic failover so a line fault becomes something you read about later rather than something that stops your day.

Talk to us about failover