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Solutions for Battery Backup of Fibre Broadband and VoIP Phone

Wednesday, Dec 29th, 2021 (12:01 am) - Score 34,576
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The rapid UK rise in “full fibre” (FTTP) broadband ISP networks and related VoIP style connectivity for home phones has one irritating drawback over older analogue copper phone services – if your house suffers a power cut then your services will all go down. But there are some simple solutions.

Under the current plan, it’s expected that traditional analogue phone services on Openreach’s (BT) national copper line network will cease to exist after December 2025. The change, which has already occurred in other countries, is inevitable as networks move to an increasingly digital all-IP (Internet Protocol) and Fibre-to-the-Premises (FTTP) focused future.

However, one often overlooked advantage of the old analogue copper telephone network is that it was powered via the network (e.g. exchange) rather than your home or office, which for example means that you’d often still be able to make a phone call even during a power cut. But this assumes you would have had an analogue phone to plug-in, since DECT (wireless) phones won’t always work in a power cut either (often only their handsets have batteries, but not the crucial base unit).


The move to all-IP connectivity solutions, whether delivered via copper or fibre optic lines, changes all that as the voice connectivity will come over your broadband link instead. But the broadband line obviously needs to be plugged in via a router, as well as Optical Network Terminal (ONT) on FTTP services. Any associated phone handsets or Analogue Terminal Adapters (ATA) would then connect into the back of your router (or via DECT, when supported by the router).

NOTE: An ATA adapter is used in situations where your router doesn’t have a phone port and can’t handle VoIP. Essentially, the ATA is a VoIP router that enables you to add this functionality without changing your router (you’ll also need an account with a VoIP provider). Examples include the Grandstream HT801 or any of Cisco’s ATA191/192 line.

Don’t operators’ supply battery backup?

Some FTTP homes were originally installed with Battery Backup Units (BBU) alongside the ONT, although Openreach stopped doing this by default in 2018 (i.e. in FTTP-only areas). Part of the reason for this is that it was only ever really needed for phone services, and it thus makes less sense now that Openreach will no longer be selling traditional voice/phone services, only data connections.

In short, the responsibility for such things has been passed on to retail ISPs, which are now able to do their own IP voice products with broadband. Furthermore, since the end of 2018, Ofcom’s “expectation” has been to “recommend only providing battery backup or other protection facilities to vulnerable consumers” (here) – this must be good enough to work for a minimum of 1 hour.

NOTE: It’s important to recognise that serious power outages, lasting days or weeks, are likely to be too expensive to cover with a battery system and may sometimes impact the operator too (i.e. having a battery may not help during extreme cases).

A Spokesperson for Ofcom told ISPreview.co.uk:

“Our relevant rules here are based around requiring providers to ensure customers can contact the emergency services, in the event of a power cut. We published guidance on this in 2018 on the measure providers can take to ensure they comply with the requirements. This has a particular focus on protecting vulnerable customers, such as those who are reliant on the landline because they don’t have access to a mobile phone or lack sufficient signal to call emergency services. If VOIP customers in this situation did suffer a power cut, they could be at risk of not being able to contact the emergency services when they need to.

Providers should take action to communicate with customers and identify those who may be at risk because they are dependent on their landline. For those customers, providers should offer a free solution to ensure they can contact the emergency services. This could be a battery back-up, or another solution – such as a mobile phone (if suitable).

But the actual rules are based on continued access to emergency services and the focus is on protecting customers who may be vulnerable due to their reliance on a landline service. So there’s not a specific requirement for battery back-up to be available to every customer.”

In practice, we haven’t seen many cases where battery systems are actually being deployed. Often, they’re not even presented as an option by the ISP and customers aren’t even told if they exist. Likewise, many dedicated VoIP providers won’t necessarily sell physical phone products in the first place.


Part of the problem above is that many ISPs don’t even attempt to identify “vulnerable” consumers when they sign-up, which is admittedly quite a tedious thing to validate, especially for smaller providers. However, we have seen cases with BT where people in this group have run into problems during power cuts (i.e. in an area with no alternative mobile signal), but after arguing with the ISP they were sent the necessary battery equipment for free. But in other cases, those who were eligible for such a backup unit were then repeatedly told it was out-of-stock.

In short, if vulnerable consumers find they have no alternative to their FTTP line during a power cut and can’t get a battery unit from the ISP, then it’s probably wise to highlight Ofcom’s guidance to the ISP and to also inform the regulator, so that they can gather evidence on how the industry is or is not responding to such situations.

However, a lot of people who aren’t in vulnerable groups would also still quite like the option of a backup solution, but if your ISP can’t provide that then there are other options.

What can you do?

We get asked about this quite a lot, especially now that the FTTP rollout has picked up its pace and more areas are starting on the copper to fibre transition. Not to mention the start of PSTN (traditional phone) withdrawal, which was mentioned earlier. The good news is that there are a couple of things you can do, and they’re often reasonably affordable.


1. Buy a Power Bank (Battery) with AC Plug Socket(s).

One of the things I do myself is to use a Power Bank that comes equipped with an AC plug socket, as well as the usual USB outputs for charging. You can find these from around £100 in the shops (see examples below) and they’re often enough to keep your router, phone handset and or ONT running for a few hours (none of those devices use much power, so they last quite well on a smaller or modest sized battery).

NOVOO Power Bank (c.£75)

Aisung AC Outlet Portable Laptop Power Bank (c.£110)

2. Buy a Small UPS.

Another option is to consider a compact Uninterruptible Power Supply (UPS), which can use a battery, flywheel or capacitors to deliver short-term power backup. Such devices can actually cost less than a Power Bank and will often give you more AC plug sockets. In addition, these kick in automatically the moment a power cut occurs, which is handy since with a pure battery bank you’d need to re-connect your devices first.

The catch is that some of them are quite unattractively bulky (words like “small” and “mini” are all relative) and may make some noise (more common on larger flywheel kit), plus they won’t always last as long as a decent power bank. However, given the low power draw of broadband kit, even some cheaper models should still be able to keep you online for 1-2 hours.. at a stretch (20-30 minutes may be more realistic for the cheaper kit).

Amazon Basics Line-Interactive UPS-550VA (c.£90)

➤ APC BACK-UPS ES – BE650G2-UK (c.£95)

Cyberpower BR700ELCD-UK Line (c.£85)

We should add that it’s also possible to buy cheaper miniature / tiny style UPS devices, but these will often only give you the smallest amount of extra time in a power cut, and they also have no space for proper AC sockets (i.e. you’ll be fiddling with trying to match connectors to your kit). Finally, you can often only really power a single device from these, so supporting a router, ONT and handset(s) together may not be viable.

Eaton 3S Mini – UPS (c.£53)

TalentCell Mini UPS (c.£70)

Hopefully this has helped to give you some idea of what is possible, although ideally, we’d much rather see home broadband ISPs providing battery backup – as a purchasable option (or free for vulnerable customers) – for those who need it, at least when such packages are taken with a bundled phone service.

Otherwise, the more you’re willing to spend on battery or UPS systems, the greater the capability. We’ve only summarised some of the cheapest options above, which may come with caveats.

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By Mark Jackson
Mark is a professional technology writer, IT consultant and computer engineer from Dorset (England), he also founded ISPreview in 1999 and enjoys analysing the latest telecoms and broadband developments. Find me on X (Twitter), Mastodon, Facebook and .
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52 Responses
  1. Avatar photo Gary says:

    With Virgin Media now having mainly moved over to “digital” phone lines on their coax network then what’s the impact here too? VM don’t have backup power to the local amplifier cabinets, so this seems like an issue with them having a large footprint. Or is it just assumed that with VM being mainly in built up areas that users will just have to use mobile coverage?

    1. Avatar photo Steve says:

      The amplifiers take their power from the main fibre node cabinet so in theory the hfc network is backed up. There are caveats, in that not all areas are designed the same, so some areas only the 48v DC telco network has battery back up, not the 60v AC for the HFC. Also this would require the modem to have battery back up.

      In the case of FTTP the cabinet will have battery back up, and as with OR products the modem and ONT/ONU will need to be backed up. I know in the past for vulnerable customers VM provided a battery back for back up of the ONT/ONU, not sure how that worked for the modem though.

    2. Avatar photo Laurence "GreenReaper" Parry says:

      I put both the cable modem and the handset base station on my UPS. Be sure to take any battery-based handsets off charge if the power goes out, as that can be expensive in terms of energy.

      Beware the Ethernet anti-shock options on these, they may limit the cable to two pairs and 100Mbos speeds.

  2. Avatar photo james smyth says:

    In general how often do people even get a power outage? Possibly if there is very ocasional building work going on near by. This is covering an almost unheard of risk

    1. Avatar photo Winston Smith says:

      Google ‘Storm Arwen’ and ‘power cuts for several days’.

    2. Avatar photo Neil says:

      We have UPSs to cover us for the infrequent but occasional power cuts here – perhaps a couple a year, for a few minutes each.

      Neither our approach, nor any of the sensible solutions offered here, would cover a power cut of a day, let alone several days.

      Is it realistic to expect ISPs to build in to everyone’s price the costs of a generator, days of fuel, regular replenishment etc., to cover those prone to longer term power outages?

      (Leaving aside the fact that this rule penalises ISPs for failures of the power system, rather than placing the onus on energy providers to solve the problem.)

    3. Avatar photo Phil says:

      In general how often do people have a crash needing their air bags deployed? In general how many fires happen that need the use of a fire extinguisher? How often does a plane crash into the ocean where people would still be alive to make use of life jackets?

      It’s not about the how often a power outage occurs, it is about the fact they do occur and when they do there may be people that will need the use of some sort of emergency backup power to keep allow them to call for help.

    4. Avatar photo Richard says:

      We live 5 miles from Salisbury city centre in Wiltshire. Rural village. Power outages average one to two a year. Last one was 5 hours. Tripplite UPS keeps router and Dect basestation powered.
      Comment about building work doesn’t make any sense, electricity network faults can be a long distance from your property…

    5. Avatar photo Just a thought says:

      Lights go out, customer trips in dark, presses call pendant, (unit is battery backed) nothing happens as OLT/modem is off…..

      Electrical fault starts fire, trips power, 999, oh dear the phone does not work, now where did I put my mobile.

      Ring 150 in the event of power failure…… “no keyboard detected press any key to continue”

      The phone line battery backup is like insurance. You hope you are never in need to make a claim, but does that mean you don’t bother with your household and content insurance?

    6. Avatar photo Meadmodj says:

      Those affected by Storm Arwen may disagree. The amount of investment we apply will depend on our individual situation which may be distance, if any of the service is overhead, subject to flooding and whether we have alternatives such as good indoor mobile signal (may change 3G,VoLTE,VoNR).

      Centralising main kit (ONT, Router) protected by UPS, using PoE to maintain minimum WIFI (for mobile via WIFI) and/or a corded phone (in a known location) is something that should be considered even in suburbia but especially in rural and isolated homesteads or where people are alone or vulnerable.

      Think of the worst case scenario and then work back until you are OK.

    7. Avatar photo MilesT says:

      Small town in North Norfolk

      Multiple short “blips” every year (enough to require clock on cooker to be reset).

      Most years at least one outage (minutes to a few hours)

      A real consideration

    8. Avatar photo WeNeedMorePowerScottie says:

      I hear an audable “Beeping” noise whenever my UPS’s are forced to kick in as the power drops. This happens more often that i imagined. Obviously, we have faced some nasty storms this past year which took out my power also Western Power were doing work in my area which resulted in ~30min power cut (fair play though they did give notice)
      My point is, there are the really obvious power cuts which can last a number of hrs but then there are those small ones which would be undetectable if not for my UPS’s tripping on. It happens more often than what I originally estimated it would happen.

  3. Avatar photo Pintx says:

    So how will you contact emergency services etc during a powercut if the phone mast is also reliant on the same electricity as is needed to power your ONT, FTTP router etc?
    I’ve had a few powercuts over the last year where the phone signal vanishes after about 15 minutes or so, these powercuts lasting between 2 to 8 hours

    1. Avatar photo Art Fish says:

      Masts usually have their own generator or UPS available.

  4. Avatar photo Optimist says:

    Power outages are a fact of life, so all equipment which has to keep going 24/7 (routers, ONTs, phone base stations and handsets) should be fitted with batteries kept topped up from the mains but ready to take over automatically (I would like to add other domestic appliances to the list, such as freezers, though for obvious reasons heaters, cookers etc. would have to be excluded because their battereies would take up most of the house).

    Even theses measures would not cope with prolonged outages as have occurred recently, so as the government doesn’t want us to use disel generators, more creative solutions may have to be considered such as battery chargers driven by pedal power.

    1. Avatar photo Meadmodj says:

      A wholistic solution is probably too much for our politicians. Ofcom and Ofgem should certainly talk together. Keeping a phone working for an hour is assuming too much and just dumping liabilities on ISPs and cost on to broadband customers isn’t the way forward.

      Our personal electricity usage is increasing including Electric cars and a considerable number of homes are fed overhead. Storm Arwen also showed us “the wrong kind of weather” can bring pylon cables down.

      The ideal answer is:
      * Upgrade to electric supply infrastructure and capacity
      * More homes with Solar Panels (if only part load) with Storage that continues to work if the grid is down (many don’t).
      * Separate selective emergency circuits in new homes
      * Ofcom to step up not only for BAU power failure measures (24/48 hours) but to ensure electric and broadband providers also have generator/battery response and repair capacity for both fixed/mobile street powered equipment as well as defined response times in total loss situations.
      * Clear and consistent advice to consumers. Including that not all fixed or mobile provision is the same (e.g OR FTTC has street powered kit, their FTTP does not. VM has street powered for both their HFC and FTTP. Other operators vary in design).

  5. Avatar photo Alistair Webb says:

    Timely article Mark, thanks. For storm Arwen style outages again, what’s the position, anyone know, for power to, say, openreach street fibre cabinets? Need to have a rough idea of power capacity availability. No point after several hours outage having a working router, if the street cabinet has no juice!

    1. Avatar photo Meadmodj says:


      In addition batteries can fail or be stolen so its important providers have contingency plans.

  6. Avatar photo Bob H says:

    A friend who doesn’t know tech asked me to solve this for her because her mobile phone coverage is poor and she lives in a village where the power goes out from time to time.

    I purchased a cheap ‘portable 12V mini UPS’ from ebay for under £25 and tested it. It works great on my router and will keep the router running for ages. As an aside it also provides a PoE injector which is not that useful for average users but works for me!

  7. Avatar photo Nick says:

    A frustrating aspect of trying to find a backup UPS is that most UPSs are marketed at commercial users to provide brief backup for high power equipment, and seem to be intended only to give enough time to shut computers/servers down safely or protect powerful kit from brief interruptions: but modern domestic modems, routers and ATAs draw very little power, often far less than is covered by the UPS power/runtime specs. It’s remarkably hard to find a UPS that is designed to provide a sustained backup at low power for a few hours. The APC UPS mentioned in the article, for example, starts its official runtime graph at 40W, twice the power drawn by my router and even more than my router, Raspberry Pi PBX and ATA combined. There is a definite gap in the market for long runtime UPSs that are specifically designed for low-power network kit.

  8. Avatar photo MilesT says:

    Providers of safety pendants are aware of the problem, and are generally replacing traditional analogue units (with internal batteries) with mobile phone 4g based units (with multi network roaming Sim cards, inclusive in monitoring contract). These also have internal backup batteries.

    Example: Doro CareIP 9300.

    1. Avatar photo Dominic Davis-Foster says:

      Won’t the 4G mast stop working in a power cut too?

  9. Avatar photo Mark says:

    For once, 4G internet has the upper hand here. Whenever we have a power-cut (typically once or twice a year out here in the sticks), I plug the 12V router into either the motorhome or the old car battery that powers the shed lights. Lasts all day if required, and all I need is a cable with a 12V connector on one end (they seem to be a standard fit, at least for Huawei and TP-Link) and crocodile clips or accessory plug on the other.

    1. Avatar photo MarkM says:

      @Mark. Assuming you have 4G coverage not everyone has that, particularly 5he area I live a small Cotswold Town the locals don’t want coverage because they feel they are a health hazard.

  10. Avatar photo 1pf says:

    Ok I am a little confused. We do not have fibre and OR will have no plans to install, (Gigaclear/Fastershire) are failing to install and it now looks as we will be ‘de-scooped’ (whatever that is). When 2025 comes over the hill does it mean I will not have an active landline because I am on copper only? No phone, narrowband etc? Mobile is really patchy. What happens in this case? Thank you

    1. Avatar photo Mark says:

      My understanding is that BT will provide an adapter for voice-only customers. Voip only needs kb/s, not Mb/s, so even 10 km+ from the exchange will work ok. We are 13 km, and ADSL syncs at around 500 kb/s, so should be fine for voice.

    2. Avatar photo Mark says:

      “Descoped” – infrastructure supplier term meaning “crossed off from coverage – too difficult/expensive”. Happened twice to us, firstly the planned new VDSL cabinet was scrapped, then the BDUK-funded FTTP went over the cost threshold.

    3. Avatar photo Lyncol says:

      Also, by 2025 will all green VDSL cabs be redundant?

    4. Avatar photo NE555 says:

      Come 2025, if you are not in the 80% who are expected to have FTTP by then, then your copper line will supply a data-only service, and a voice “landline” service will be provided via a telephone port on your router.

      Any voice-only copper lines will be converted to low-speed data lines (0.5M up and down), again with a router that you plug your phone into.

      > Also, by 2025 will all green VDSL cabs be redundant?

      No, quite the opposite. They will be essential for providing service over copper – because there will be no service from the local exchange.

      They will eventually be removed, but only in areas with both 100% FTTP availability and takeup (i.e. after all users have been forced from copper to FTTP)

  11. Avatar photo Tom says:

    I’m worried about the safety compliance of “AC Outlet Portable Laptop Power Bank, Universal 31200mAh 100W Travel Laptop Charger & Fast Charging External Battery Pack for MacBook, Acer, HP, Samsung, Dell, ASUS, Lenovo, Notebook “.. the UK plug socket doesn’t look like it meets regulations.

    1. Avatar photo The Facts says:

      Lethal and illegal. Please remove link.

    2. Avatar photo ToneDeaf says:

      Agree – quite a bit of exposed metal in that mains output socket!! No shutter protection as on a standard domestic outlet.

    3. Avatar photo Mark says:

      No shutters over live pins! Absolute rubbish – disappointing that ISPreview promote such dangerous junk.

  12. Avatar photo MarkM says:

    We’re in the Openreach commercial fttp rollout but on exchange only lines, which there are a hundred or so terrace properties/streets so surely Openreach will upgrade everyone to Fttp approx 2500 properties plus 300 business users on exchange.

    1. Avatar photo Sunil Sood says:

      Yes, they are bound to upgrade you to FTTP – especially if they want to close the exchange (which they are bound to want to do)

  13. Avatar photo Timmy Mallet says:

    A flywheel UPS?

    I want one!

    1. Avatar photo florca says:

      Maybe you don’t… The large datacentre where I worked in the mid-90s had a pair of flywheel UPSs sited in a small building next to the datacentre, sized to power the site though an initial power cut and start the massive diesel backup gensets.
      Shortly after a routine service the mainshaft bearings on one of the flywheels seized, melted, the flywheel broke free and through its cage, through the wall of the building, across the car park and ended up embedded in the trunk of a large tree roughly quarter of a mile away across some fields. Had the thing been spinning in the other direction it would have gone straight through the datacentre taking out a collection of the most expensive IBM mainframes money could buy..

  14. Avatar photo yorrrick says:

    We have a 12v car battery which supplies our router, all the network switches, the aerial amplifiers and the DAB radio so our broadband and radio are not affected during a power cut. Much simpler and cheaper to manage than a 240v UPS.

  15. Avatar photo Bob says:

    At present there appear to be no suiable product for just backing up a VOIP phone. I suspect ther residential use of VOIP is small at the moment which probably accounts for the lake of a suitable product

  16. Avatar photo Bob says:

    There seems to be a possible backup for residential VOIP. It claims to give 1 hour back up as recomended by OFCOM No indications though of any UK or EU approvals or who makes it


  17. Avatar photo Bob says:

    I have managed to identify the manufacturer and it does have the relevent UK/EU approvals

    Link here: https://www.powerinspired.com/brochures/br-ipower-h.pdf

  18. Avatar photo Darren Reid says:

    You can also buy something like this and plug it into usb powerbank which are very cheap. Added bonus that you can charge a usb power bank in most cars if a long power cut occurs.

  19. Avatar photo RaptorX says:

    AAISP have been ahead of the curve for VOIP for over a decade, offering VOIP services as standard. Another great thing about this ISP.

  20. Avatar photo Guy Cashmore says:

    My ONT and router are both directly connected to a 12v car battery, nothing special, just one I picked up in Halfords that was on offer. The battery is kept charged by 4A ‘maintenance’ charger, the type classic car owners leave connected all winter. Couldn’t be simpler really, it will keep everything working including the VOIP for a couple of days without power.

    1. Avatar photo 5G_Infinity says:

      Is that an OR Huawei ONT, how do you convert from 12V to what the ONT needs?

  21. Avatar photo Ixel says:

    I’m surprised the ‘iPower 12Vdc UPS System’ didn’t get mentioned, currently about £40 I believe. From Power Inspired (recently renamed to 1VA UPS Systems) in the UK.

    1. Avatar photo PrinceOfTheWirral says:

      I’m on the TalkTalk VoIP trial, they supplied me with two Powerinspired iPower units. One for the router and one for the ONT. I have no mobile coverage, so need it for emergency calls.

  22. Avatar photo alan says:

    Re james smyth comment:
    In general how often do people even get a power outage? Possibly if there is very ocasional building work going on near by. This is covering an almost unheard of risk

    Obviously doesnt live in Rural Suffolk where out supply arrives on overhead power lines across fields etc, from the Sub Station about 8 miles way
    Only last Sunday we had an intermiitent supply all morning

  23. Avatar photo Margaret Copland says:

    This past winter, we have had 2 power cuts which lasted 6 days each. The mobile masts also had no power. When copper phones lines are switched off, there is no solution for us but to buy a generator (so much for net zero targets).
    However, another problem with the switch off is that many areas, still relying on the copper lines for their internet connection may not have fast enough speeds. My telephone provider says I don’t have fast enough speeds so will have no telephone service at all! That assumes internet over copper lines will still work.

  24. Avatar photo Paul J says:

    I have full fibre to the house! Our service is provided by BT We were told that we must now convert to VOIP! Our mobile phone coverage is as near zero as makes any difference! And I am considered medically vulnerable! I have argued and argued with BT that they must provide battery backup/UPS referring them to OFCOM guidance. After months of telephone calls and repeatedly explaining OFCOM “guidance” they finally provided a single C13? socket battery to plug into the router which will last one hour on standby and/or 4 minutes of user service. This does not provide power to the ONT or the DECT handset! So, in isolation is useless. When explaining the “shortcomings” of this the customer service agent states that as we have been sent one battery the “system” will not allow any additional help!!! BT will simply not meet their obligation provide the ability to contact the emergency services in the event of a power failure.

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