TL;DR
Does VoIP work during a power cut? In short — no. VoIP phones stop working in a blackout because your router, modem, and internet service all rely on electricity. Without power, the internet connection that VoIP requires goes down.
But that doesn’t mean you have to lose service. With the right setup, you can stay connected even during a power cut. For example, an uninterruptible power supply (UPS) can keep your router and VoIP adapter running, while mobile failover ensures calls are diverted to your smartphone when your broadband is offline.
At Plexatalk, we provide both residential and business VoIP services in the UK designed with reliability in mind. By adding simple backup options, you can ensure you never miss important calls — whether it’s a family member during an emergency or a client in the middle of a blackout.
So, while the technical answer to “Does VoIP work without internet?” or “Is VoIP reliable in a power cut?” is no, the practical answer is that you can keep talking with the right VoIP provider and setup.
Why Traditional Landlines Worked in a Blackout
One of the biggest reasons people ask, “Does VoIP work during a power cut?” is because traditional landlines used to keep working even when the lights went out. The old copper-based PSTN (Public Switched Telephone Network) lines carried their own low-voltage electrical current directly from the telephone exchange. That meant even if your house lost mains power, you could still pick up the phone, hear a dial tone, and make or receive calls. For decades in the UK, this reliability during a blackout was seen as one of the strongest advantages of landlines.
VoIP, by contrast, works very differently. Instead of drawing power from the exchange, VoIP services rely on your broadband connection and home equipment — such as your router, modem, and VoIP phone or adapter. All of these devices need electricity to function. If your home loses power, your internet connection goes down, and with it, your ability to make calls. That’s why the answer to “Is VoIP reliable in a power cut?” is usually no — unless you put backup measures in place.
This is where providers like Plexatalk step in. Our residential and business VoIP packages can be paired with simple solutions like battery backup systems or mobile call forwarding. That way, even though VoIP depends on broadband and electricity, you won’t lose your voice service the moment there’s a power outage in the UK.
Why VoIP Stops Working Without Power
A common concern is, “Does VoIP work without internet or during a power cut?” The answer comes down to how VoIP is delivered. Unlike the old PSTN lines, VoIP runs over your broadband connection, which depends on equipment inside your home. Your router, modem or ONT (if you’re on fibre), and VoIP handset or adapter all need electricity to function. If there’s a blackout, these devices switch off — and when they’re off, so is your phone service. That means no inbound or outbound calls, including emergency calls to 999.
This reliability issue has been taken seriously by UK regulators. Ofcom requires all VoIP providers to make sure customers — especially vulnerable users — can still call emergency services in the event of a power outage. As a minimum, providers must offer a solution that guarantees at least one hour of backup power. In practice, this usually means a small battery backup device (UPS) that keeps your router and VoIP hardware running long enough to make urgent calls during a blackout.
At Plexatalk, we comply with this rule by ensuring that all residential customers have a way to make emergency calls during a power cut. This may be via our VoIP mobile app, or where that isn’t suitable, a battery backup (UPS) device. Vulnerable customers receive these solutions free of charge, as required by Ofcom.
Ofcom Rules and Provider Solutions
With the UK’s copper landline network being switched off by 2025, Ofcom has set clear rules for how VoIP services must handle power outages. Since VoIP depends on electricity, Ofcom requires providers to ensure that customers can still contact 999 during a blackout. To meet this, many major providers — including BT, Vodafone, and Zen — supply battery backup devices that keep your router and fibre ONT powered for a limited time. Depending on the model, these can last anywhere from 1 to 7 hours, giving households a safety net in case of a power cut.
Importantly, vulnerable customers can request these backup devices for free. This ensures that those who rely most on their phone service are not left without a way to call emergency services. Ofcom’s full guidance can be found on their official website here.
To comply with Ofcom rules, Plexatalk ensures that all residential customers can make emergency calls during a power cut. For many households, this can be done easily via our VoIP mobile app, which works over 4G/5G. Where a mobile app isn’t suitable — for example, if there’s limited signal or the customer relies on a fixed phone — we provide a battery backup (UPS) option to keep your equipment running for at least one hour. Vulnerable customers can receive these backup solutions free of charge, in line with Ofcom guidance.
How to Stay Connected in a Power Cut (Practical Fixes)
So, is VoIP reliable in a power cut? On its own, not really — but with the right setup, you don’t need to lose service during a blackout. Here are some proven ways to keep your phones working when the electricity goes out:
- UPS (Uninterruptible Power Supply) – A small battery backup can power your router and VoIP adapter for several hours. Simply plug your essential devices into the UPS so your broadband and phones stay online during a short outage.
- VoIP Mobile Apps – Most providers, including Plexatalk, offer apps that let you make and receive VoIP calls over 4G/5G. If your Wi-Fi or router goes down, your mobile data keeps you connected.
- Automatic Call Forwarding – Set up your VoIP service to automatically redirect calls to your mobile if your broadband connection fails. That way, even in a full blackout, you won’t miss a call.
- PoE Phones + UPS – In business environments, powering VoIP desk phones via Power over Ethernet (PoE) switches connected to a central UPS can keep an entire office system running.
- Corded Analogue Phone (if supported) – Some broadband hubs still feature an analogue socket with limited backup power, allowing a basic wired phone to work for emergencies.
At Plexatalk, we help both residential and business VoIP customers in the UK put these safeguards in place. Whether it’s setting up mobile apps, configuring call forwarding, or advising on the right UPS, we make sure you’re not left asking “Does VoIP work during a power cut?” — because your service stays ready when you need it most.
Real Risks: Rural Homes and Vulnerable Users
When discussing VoIP power outage UK scenarios, it’s important to recognise that not all homes and businesses are affected equally. In urban areas with strong mobile coverage, a blackout might be a minor inconvenience — you can usually fall back on 4G or 5G. But for rural households or properties in mobile dead-spot areas, a power cut can mean complete disconnection. If broadband is down and mobile coverage is patchy, you can’t rely on your phone line for emergencies.
This is especially concerning for vulnerable users who may depend on their landline for medical support, care services, or urgent calls. Public forums and UK news outlets have already raised concerns about the retirement of copper landlines, with headlines questioning “Is VoIP reliable in a power cut?” and highlighting the risks to older or isolated residents. The issue is real, and regulators like Ofcom have acknowledged it.
The good news is that solutions exist. From UPS devices that keep your router alive, to automatic call forwarding and VoIP mobile apps, there are practical ways to avoid being cut off. That’s why Plexatalk provides mobile app access for most households, and free UPS backup for vulnerable users who cannot rely on mobile coverage, ensuring compliance with Ofcom rules.
Why Choose Plexatalk for Reliability
With the copper network being retired across the UK, more people are asking, “Does VoIP work during a power cut?” and “Is VoIP reliable in a blackout?” The truth is, reliability depends on how well your VoIP service is set up — and that’s where Plexatalk makes a difference.
Our residential and business VoIP services are designed with resilience in mind. Every customer gets access to the Plexatalk mobile app, so you can make and receive calls over 4G/5G if your home internet goes down. We also include automatic call forwarding as standard, meaning your calls can be redirected instantly to your mobile if there’s a broadband or power outage.
For businesses, we’ve tested our hardware with a range of UPS (Uninterruptible Power Supply) units, ensuring your routers, switches, and VoIP desk phones can be kept online during a blackout. This keeps offices operational and customer-facing even when the mains power is off.
We also provide extra support for vulnerable customers, in line with Ofcom guidance. That means recommending the right backup solutions and supplying options where needed, so no household or business is left unprotected during a VoIP power outage in the UK.
With Plexatalk, you don’t just get a phone service — you get peace of mind that your connection is there when you need it most.
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Stay Connected with Plexatalk
So, does VoIP work during a power cut? Technically, no — without power, your router, modem, and VoIP equipment can’t function, which means no calls in or out. But that doesn’t mean VoIP has to leave you stranded in a blackout. With simple backup options like UPS units, mobile apps, and call forwarding, you can keep your line active even when the lights go out.
At Plexatalk, we believe VoIP should give you more reliability, not less. That’s why our services come with built-in safeguards: a mobile app for backup calling, automatic call forwarding, hardware tested with UPS devices, and extra support for vulnerable customers in line with Ofcom guidance. Whether you’re a family worried about emergency calls, or a business that can’t afford downtime, we’ll make sure your VoIP setup is ready for anything.
VoIP doesn’t have to leave you cut off during a power cut — you just need the right setup.
👉 Talk to us today about keeping your landline working during blackouts. Plexatalk can help you stay connected.