Solar battery and NBN backup during Perth power outages

During a Perth blackout, most homes lose their internet along with the power. A home battery can keep it running, but only if three things line up: your NBN connection type actually needs in-home power, your battery system has backup (EPS) capability, and your router and NBN box sit on the backed-up circuit. Miss any one of those and your internet drops with everything else.

Here's how to check each piece for your own setup, plus a cheap fallback if you don't have a battery at all.

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Which NBN connection types need power to keep working?

FTTP (Fibre to the Premises). The NBN box in your home, the NTD (Network Termination Device), needs mains power to run. No power, no NTD, no internet. To keep this connection alive in an outage, you need to power the NTD itself.

The NTD typically draws 5–10W. Your router adds another 5–15W. Total draw for basic internet sits around 10–25W. That's tiny.

FTTN/FTTB (Fibre to the Node/Building). Here the signal runs over the copper phone line from a street-side node, straight into your router. There's no NBN box inside your home. The node itself carries its own backup batteries, maintained by NBN Co, so your connection can survive an outage without any home battery at all, as long as the copper line and the node both stay up.

In practice, FTTN/FTTB connections often stay online for several hours during a Perth outage, running on the node's batteries, with nothing needed at home beyond keeping your router powered.

FTTC (Fibre to the Curb). Similar story to FTTP: there's a DPU (Distribution Point Unit) at the street and a small NTD inside your home. That NTD needs power. No power, no internet, unless you back it up.

HFC (Hybrid Fibre Coaxial). Runs over the old cable-TV coax. The in-home NTD needs mains power too. Same rule: an outage means no internet unless you power the box.

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What do you need to keep the internet running in an outage?

For FTTP, FTTC, and HFC, where an NTD inside your home needs power, three things have to line up.

A battery only keeps your internet running in a blackout if all three line up. Not one or two of them, all three.

1. EPS-capable battery hardware. A standard grid-tied solar and battery system shuts down in an outage, by design, under anti-islanding requirements. Only a system with EPS (Emergency Power Supply) capability can power anything while the grid is down.
2. Your router and NTD on the backed-up circuit. If your EPS system only backs up specific circuits, plug the router and NTD into a GPO that sits on that backed-up circuit. Many EPS systems back up one dedicated circuit or a handful of specific GPOs, not the whole switchboard.
3. Enough battery capacity. The load here is tiny, 10–25W. A 10kWh battery at that load would theoretically run for 400 to 1,000 hours. In reality you'll be running other things off the same EPS circuit, phone chargers, a fridge, some lighting, and that eats into it.

FTTN/FTTB is the exception. Your internet may already survive an outage without any battery, since all you need to keep powered is your router (5–15W).

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What could stop a battery or UPS from backing up your internet?

Does NBN Co still supply a battery backup unit?

Not the way it used to. NBN Co has moved away from including a Battery Backup Unit (BBU) in residential FTTP/FTTC installations in recent years. The in-home NTD no longer comes bundled with its own backup battery. If your connection needs that box powered, backing it up is on you.

Can any EPS system power a modem and NBN box?

Not every one, in theory. Some NTDs want a stable sine wave input. In practice this rarely bites, because the waveform in backup mode comes from the inverter, not from the battery pack itself. If a specific NTD or router is fussy, your installer can confirm the backup output against the inverter's datasheet before you rely on it. A basic UPS handles the job too, for just the router and NTD.

How long does it take a battery to switch over?

When the grid fails, an EPS system needs a moment to switch to battery. Modern hybrids are often under 10 milliseconds, which routers and NTDs ride through without noticing. Not every system is that quick though: some take several seconds, long enough to reboot a router and drop the connection anyway. Ask your installer for the switchover time on your specific inverter. If uninterrupted internet genuinely matters to you, put a small UPS on the router and NTD as well, so the connection rides through the transfer regardless of how fast the battery picks up.

Can you still call 000 if the internet drops?

Usually, as long as a mobile network is still reachable. A mobile phone reaches 000 with no internet connection at all, which is exactly why you shouldn't lean on a VoIP (internet phone) handset when the power's out. Mobile towers run on their own backup power though, and a long or widespread outage can exhaust it or cut the tower's backhaul, leaving nothing to connect to. If anyone in the house has a medical or emergency-communication need, plan for it specifically: keep a charged mobile on a network with good coverage where you live, and test it before you need it.

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Is a UPS enough if you don't have a home battery?

If you don't have a home battery and just want the internet to survive short outages, a small UPS (Uninterruptible Power Supply) is the simplest fix going.

• A basic UPS built for home routers costs well under $200 and can typically keep a modem, router, and NTD running for a few hours during an outage.
• It plugs into the wall and switches to its own battery the moment power fails. No solar, no home battery system required.
• It's not a substitute for a home battery: no solar self-consumption benefit, no backup for anything else in the house. It's a cheap, dedicated fix for internet only.

If you're weighing a UPS against a bigger backup setup entirely, our guide to battery and generator backup for Perth homes covers the wider equipment question.

For Perth households who just want the internet to ride out short storms or Western Power maintenance work, a UPS is often the practical, low-cost answer.

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How do you set up an existing battery to back up the internet?

If you already have a battery with EPS mode, get your router and NTD (where one applies) onto the backed-up circuit. Usually that's as simple as plugging them into a GPO inside the EPS zone. Ask your installer to point out exactly which circuits or GPOs that covers.

The internet's power draw is so small it barely touches your battery's runtime for everything else: fridge, lighting, phone charging included.

For the fuller picture on what solar and battery backup actually delivers, and where it falls short, during a Perth blackout, see our guide to solar and battery backup for Perth blackouts. And if you're working out exactly how many hours your own setup would last, our guide to battery backup duration in Perth walks through the sums.