Keep the whole chain powered, from the fibre box to your screen, and plan a second internet route for wide outages. Small UPS units cover one or two boxes for a limited time. A house backup battery with a no-break output carries the whole office, and the rest of the house, without even a restart.
You run your business or your job from a home office. The client call starts at ten. Then the lights flicker, the screen stays on because the laptop has a battery, but the call freezes. The router in the cupboard is dark. One remote worker wrote: "Losing internet in the middle of meetings or while I'm working on documents is always in the back of my mind."
What most people miss is that a home office is a chain, and the weakest link sits in the network cupboard. The fibre box, the modem, the switch, the Wi-Fi points and often the alarm all need mains power. Even a dip of a second restarts them, and a modem can take minutes to come back. A small UPS per box helps, until you have five of them with five batteries to replace. A battery owner in a Dutch-language Reddit group asked what nobody plans for. How do you make sure "there is still enough in the battery at that moment"?
In a house in Peer the entire house is on no-break, on one battery system. When the grid fails, all the devices still function.
Which devices does a home office really need in a power cut?
Everything between the fibre in the street and your screen needs power. Most of it has no battery at all.
| Device | What happens in a power cut | What keeps it running |
|---|---|---|
| Laptop | Runs on its own battery for a few hours | Its battery; a charger on a backed-up socket |
| Desktop PC and screens | Switch off at once; unsaved work is lost | A no-break supply that takes over fast enough |
| Fibre box and modem | Internet stops as soon as the modem loses power | A small UPS or a no-break circuit |
| Switch, Wi-Fi points, PoE cameras | Network is gone even if the modem is on | The same backed-up circuit as the modem |
| NAS or home server | Hard stop, risk of data errors | No-break supply; a clean shutdown if the outage is long |
| Alarm system | Proximus: the alarm signal goes to the control room via the modem | Power for the modem, not only for the alarm panel |
| Phone | Works on mobile while the antenna has power | A charged phone and a powerbank |
Tip
Walk to your network cupboard and count the plugs. That number tells you how many small UPS units you would need, and how many batteries you would have to replace over the years.
Does fibre internet still work when the power is out?
Only if your modem has power, and only if the network outside still works. Your home battery controls the first part, not the second.
How your internet reaches your laptop
Proximus is clear about the part in your house. As soon as the modem fails for lack of mains power, "the internet connection also drops". A phone line over fibre or VoIP stops at the same time. For a wide outage it adds: "If the electricity fails in a zone, Proximus Internet, Voice-over-IP and TV will not work."
Mobile data is your second route, with limits. Proximus states that its antennas have batteries for a power cut of at least 2 hours. During that time you can call and send texts. Mobile internet works for about the first quarter of an hour in the outage zone, then less and less. An antenna can also cover a larger area than the outage zone. So you may keep mobile service at home while the street is dark, or lose it while your street still has power.
| Type of power cut | Your fibre or cable internet | What to plan |
|---|---|---|
| Dip of a second or less | Modem restarts and can take up to 2 minutes (Telenet) | A supply that switches over without a restart |
| Fault in your house or street | Works if your modem has power and the network outside still has power | Backed-up modem, switch and Wi-Fi |
| Planned works by the grid operator | Same as a local fault; you know the time window in advance | Charge the battery fully before the window |
| Wide outage in a whole zone | Proximus: internet, VoIP and TV do not work | Mobile hotspot, or work from another location |
Why does a one-second dip cost you five minutes?
Because the network gear restarts from zero, and a modem is slow to start. Telenet writes that a modem can take up to 2 minutes to start up.
After the modem come the switch, the Wi-Fi points and the connections of your laptop and your video call. A forum member described the same pattern: short dips "don't take most things offline, except my audio receiver and Internet modem". The laptop survives on its battery, but it has nothing to connect to.
This is where switchover time matters. The inverter-charger in our home batteries takes over the supply in the event of a power failure. Victron states it happens "so fast (less than 20 milliseconds) that computers and other electronic equipment will continue to operate without disruption". For your network gear, that means no restart, so no lost minutes.
Not every home battery does this. Many only store solar power and stop with the grid, and a plug-in battery has no real back-up output. Read what a plug-in battery can never do.
Small UPS units, a power station or a whole-house battery: what fits a large home?
Small UPS units protect one or two devices for a limited time; a whole-house battery protects the office and the rest of the house. The right choice depends on how much must keep running, and for how long.
| Solution | What it covers | Switchover | What to watch |
|---|---|---|---|
| Small UPS per device | Modem, switch or PC plugged into it | Fast, within the rating of the UPS | Short runtime; one battery per box to replace |
| Portable power station | What you plug into it | Depends on the model; not every one switches without a gap | You must set it up; limited power |
| Plug-in home battery | Mainly solar storage | No real back-up of the house circuits | See the plug-in article |
| Whole-house battery with no-break output | Office, network, heating, pumps, alarm | Less than 20 ms on a MultiPlus-II | Wiring of the board; reserve charge |
Small solutions do work for a small need. One forum member says a small power station keeps his NAS and router running as a UPS for about 5 hours. In a large home, the office is rarely the only thing that must keep running. The heating, the pumps, the gate and the alarm count too.
How the switchboard is split for full back-up is a wiring question. We explain it in how a full no-break house is wired. For companies with server rooms and production lines, read small UPS units or one central battery.
Working from home in a large house? Send us the list of what must keep running in a power cut.
How do you make sure the battery is not empty when the power fails?
Set a reserve that the battery only uses when the grid fails. Without it, a battery that powered your evening can be empty by the time an outage comes.
Victron ESS has a setting for this: "Minimum SoC (unless grid fails)". Down to that level, the battery covers your normal use. Below it, the battery only discharges further when the grid has failed. So the reserve stays available for a power cut.
How big should the reserve be? Take the loads that must run in an outage and the hours you want to bridge. For example, an office, network and fridge that together draw 300 W need at least 1.2 kWh for 4 hours, plus a margin for losses. Add the heating or pumps if they are on the back-up board. Before planned works of the grid operator, charge the battery fully.
Does your battery also trade on dynamic prices? Then ask how the reserve for outages is kept. See also how a heat pump runs on a home battery in a power cut, because heating is usually the biggest load in winter.
What else must keep running when you work from home all day?
The house around the office. A warm room, water, a working gate and an alarm matter as much as the internet during a long working day.
- Heating and hot water: a heat pump needs power, and its start current must fit the inverter.
- Pumps: a well pump, sump pump or sewage pump can flood a cellar within hours. Read which pumps must keep running in a power cut.
- Gate, garage door and alarm: you need to get in and out. A connected alarm, such as the Proximus one, sends its signal via the modem.
- Fridge and freezer: one forum member mainly wanted to keep the fridge, the freezer and the internet on during an outage.
On three phases, check how much power the battery gives per phase: read about the three-phase home battery for full back-up. Do you run a business with a workshop at home too? Read one connection, two uses.
What if the outage lasts longer than your battery?
Plan the steps in order: battery, solar, then a generator, and a mobile route for the internet. A whole working day is a different outage than a dip.
- Step 1: Check whether the neighbours have power. Fluvius asks you to first find out whether the problem is in your house or on its grid, and shows current outages on its website.
- Step 2: Switch heavy loads off, so the office, network, heating and fridge can run longer on the battery.
- Step 3: Let the solar panels recharge the battery, if the system keeps them running in island mode.
- Step 4: Start a generator on the inverter input for outages of a day or more. Read how a generator recharges a home battery. The GX controller can start a back-up generator automatically.
- Step 5: Is the internet of the whole zone down? Switch to your phone hotspot for the first quarter of an hour, and move urgent calls to the phone.
How do we set up a home office on back-up?
We start from what must keep running and for how long, then we build the back-up around it. For a home office, that list always includes the network cupboard.
In Peer the whole house runs on no-break on a single-phase connection, with 5 kVA and 15.4 kWh. In Temse a single-phase house has full back-up, and we can always give single-phase or 3x400 V systems an off-grid mode. In Kapellen the owner gets alerts on his phone, for example when the battery is full or charges from the grid.
- Step 1: We measure your consumption and list the loads that must run in a power cut: office, network cupboard, heating, pumps, gate, alarm.
- Step 2: We check the switchboard: can the whole house go behind the inverter, or only the essential circuits?
- Step 3: We choose the inverter power per phase and the battery size, and we set the reserve for outages.
- Step 4: You follow the system in the free VRM app and portal, remotely, or locally on your own network (LAN).
Our team includes three certified battery experts. See what our home batteries can do for a large home, or read first which home battery keeps working in a power cut.
Frequently asked questions
Do I still need a UPS if I have a whole-house battery with back-up?
Usually not for switchover: Victron states computers keep running on the no-break output. A small UPS can still make sense for a device that is not on the back-up board.
Can I still call the emergency number in a power cut?
Proximus writes that you can call all emergency numbers on your mobile as long as the antenna works. If antennas go down, operators route 112 calls via another operator's antenna. A phone line over fibre stops when the modem loses power.
What should I do when the power comes back?
Proximus advises to let the modem start up fully first, then switch on the other devices. Before a planned outage, it advises to switch off the modem and other devices so they are less at risk of damage.
Does my home office need three-phase back-up?
Not for the office itself: it draws little power. Three-phase back-up matters for the house around it, such as a three-phase heat pump or other three-phase loads.
Want your home office to keep running in a power cut?
Tell us what runs in your home office and network cupboard, your connection type and what else must keep running in the house. One of our battery specialists will tell you which back-up set-up fits, and how much reserve you need. First want to see how the board is wired? Read how a full no-break house is wired.