By Rob Kavanagh · ex-telco tech · connectivity, comms and keeping remote places reachable
“After my solar array died during a Black Saturday bushfire in 2013, I learned that satellite backup isn't optional; it's the only thing that kept me connected when the grid failed.”
Look, if you're off-grid in Australia, your phone better work when the grid dies. No more "oh, the internet's down" excuses. Here's the real deal: VoIP on solar with satellite backup. No fluff.
Reliable voice and messaging off the grid is a stack of three things working together: a low-power VoIP handset on your local network, a solar/LiFePO4 supply to keep it running, and a satellite backup for when there is no terrestrial signal at all. This article lays out the specs, the options, and the failure modes I care about for a property in Central Queensland — written for anyone building or upgrading a similar setup.
In remote Australia, a working phone system needs to handle three conditions:
1. Day-to-day voice calls over VoIP while you're inside your network footprint.
2. Outside-Wi-Fi messaging and check-ins when you're away from the property but still inside the mobile or cellular fringe.
3. True satellite failover for when there's no terrestrial signal at all — emergencies, travel into black spots, or extended outages.
Most beginners conflate (1) and (3). They aren't the same product category. A satellite communicator is not a replacement for a VoIP handset, and a VoIP handset is useless outside your router's range. Plan for both.
For day-to-day calls at the property, VoIP over satellite internet is the standard combination. Starlink is the most commonly cited option in the Australian off-grid market: the SpaceTek guide (date-stamped reference, accuracy not independently verified) describes it as the best overall off-grid satellite internet option, with 150+ Mbps speeds, 30–40 ms latency, broad Australian coverage weighted toward populated areas, $599 equipment cost, and $120/month pricing. Note that Starlink coverage figures are population-weighted rather than area-weighted — vast interior regions of Australia remain unserviceable.
Power draw is not modest — the Starlink user terminal (dish) is the dominant load. Real-world figures from Starlink and independent reviewers put average draw at roughly 50–100 W during normal operation, with sleep/idle in the 20–40 W range. The Wi-Fi router adds another 5–15 W. This matters when you're running everything off solar, because the dish alone can consume more than the rest of the comms stack combined.
The voice quality on VoIP over Starlink is acceptable for normal calls. Latency in the 30–40 ms range is well below the threshold where conversation feels delayed. The cost per minute is effectively zero on an unmetered plan, which makes VoIP dramatically cheaper than satellite voice for daily use — that part of the old version of this article holds up.
For the Aussie reader: if you're at the property and within your own Wi-Fi footprint, make the call on VoIP over Starlink. Don't burn satellite voice minutes for a chat with your supplier in Rockhampton.
Comms equipment is low-draw at the handset end, but the Starlink dish dominates the budget. A rough budget for a continuously-running phone system:
| Component | Approx. continuous draw | Notes |
|---|---|---|
| Starlink user terminal (dish) | 50–100 W typical, 20–40 W idle/sleep | Dominant load; spikes during heavy use, slewing, or snow/rain |
| Router/switch | 5–15 W | Depends on features (Wi-Fi, VPN, firewall) |
| VoIP handset on cradle | 1–3 W | Almost negligible |
| Smartphone charging (intermittent) | 5–10 W | Only while on charge |
LiFePO4 vs lead-acid for comms backup: LiFePO4 batteries have a longer cycle life and a higher usable depth of discharge than lead-acid. For a comms-only system that cycles daily, that's a real advantage — you can use a much smaller-rated battery bank without shortening its life. A 100 Ah LiFePO4 bank at 12.8 V nominal stores about 1.28 kWh nameplate, of which roughly 1.02 kWh is usable at 80% depth of discharge. That bank will run a 30 W handset/router-only load for well over 24 hours with no sun, but a realistic Starlink-inclusive load of 80–100 W (dish + router) drains the same bank in roughly 10–15 hours — which is why the array and battery sizing below matter.
Sizing rule of thumb: target at least 48 hours of comms autonomy with no solar input. That covers overnight, a cloudy day, and a generator-free buffer. Keep the comms gear on a dedicated DC circuit (appropriately gauged DC-rated cable, inline fuse or breaker sized to the conductor, correct polarity observed) or a small pure-sine-wave inverter on the AC side — comms electronics don't tolerate modified sine well.
When there's no Starlink, no mobile signal, and no Wi-Fi, you need a satellite communicator. These are not phones in the traditional sense — they're two-way text and SOS devices that pair with your smartphone via Bluetooth and an app.
Two products with Australian availability come up repeatedly:
A compact, rugged device that pairs with a smartphone or tablet to deliver two-way messaging, location sharing, weather forecasts, and SOS alerts even outside mobile or Wi-Fi coverage. It's offered in Australia by Exceed ICT for adventurers, FIFO workers, and remote-area professionals.
Strengths: long battery life, proven Iridium network (true global coverage), straightforward app integration. The ZOLEO is a solid general-purpose pick if you want one device that works everywhere in Australia.
HMD OffGrid provides text messaging, location sharing, and SOS services via satellite connection. Specific capabilities confirmed by the manufacturer:
Build and plan details:
Note: "select areas" is the operative phrase. HMD OffGrid coverage is not blanket-continental — confirm your specific region is covered before relying on it for safety-critical communication.
You want both, but for different jobs. If you're trying to run a VoIP call on a ZOLEO or HMD OffGrid, you've bought the wrong tool — those devices are low-bandwidth text/SOS products, not voice terminals.
Don't forget to charge the messenger. The HMD OffGrid claims a 3-day battery life, but battery life testing depends on usage conditions; carry appropriate charging solutions for extended off-grid trips. In practice:
A non-exhaustive list of failure modes I watch for:
This article covers consumer comms gear and DIY solar basics. Australian standards apply across fixed electrical, solar, and battery installations — the relevant documents are AS/NZS 3000 (Wiring Rules), AS/NZS 5033 (PV array installation), and AS/NZS 5139 (battery installation). State and territory regulations require licensed installer sign-off for most fixed solar and battery work regardless of system voltage or capacity; the 48 V "arc" threshold sometimes cited is not a safe boundary for deciding whether to use a licensed electrician. Call a licensed professional when:
For everyday comms setup (router, VoIP handset, USB-powered messenger), a competent owner can do the work safely, but fixed solar and battery installation is a licensed trade in Australia — even at "small" scale — so confirm your state's state rules before pulling cables into a fixed battery system.
A backup system that hasn't been tested is just expensive shelf-furniture. A simple quarterly routine:
1. Starlink: confirm online, speed-test, check for firmware updates.
2. VoIP: make a 5-minute test call in and out.
3. Power system: check battery state-of-charge, run a brief load test if your inverter supports it, inspect cabling and fusing.
4. Satellite messenger: send a check-in message, confirm two-way, verify subscription is active, charge to 100%.
5. Logs: note any anomalies, even minor ones. Patterns matter.
Q: Can I make normal phone calls over Starlink?
A: Yes. VoIP quality over Starlink is good for daily calls — 30–40 ms latency (per the SpaceTek guide, verify against Starlink's published specs) is well within acceptable range. Use a VoIP handset, softphone app, or your mobile's Wi-Fi calling.
Q: Do I still need a satellite messenger if I have Starlink?
A: Yes, if you leave the property. Starlink is a fixed-site broadband service. A satellite messenger is your link when you're away from the Wi-Fi footprint with no mobile signal.
Q: How long will a LiFePO4 battery run my comms gear?
A: A 100 Ah LiFePO4 bank at 12.8 V nominal stores about 1.28 kWh nameplate, of which roughly 1.024 kWh is usable at 80% depth of discharge. That bank will run a 30 W handset/router-only load for well over 24 hours. If you're powering a Starlink dish as well (realistic 80–100 W combined load), expect roughly 10–15 hours on the same bank — which is why the array and battery sizing in the power-supply section matter.
Q: Is ZOLEO or HMD OffGrid better?
A: Different design points. ZOLEO uses Iridium (broad global coverage) and is sold in Australia by Exceed ICT. HMD OffGrid offers IP68/MIL-STD-810H ruggedness, 3-day battery, and SOS coordination via Overwatch x Rescue™ — but verify HMD OffGrid satellite coverage for your specific region before relying on it for safety-critical communication, because coverage is in select areas only.
Q: What's the cheapest satellite internet plan available?
A: The SpaceTek guide lists the most affordable satellite internet option starting at $49.99/month on a 24-month contract. Starlink (cited as best overall in that guide) is $599 equipment + $120/month — verify on Starlink's own site, as third-party guides can lag.
Q: Are satellite messengers legal everywhere?
A: No. Certain regions may restrict or prohibit the use of satellite communication devices and users are responsible for complying with applicable laws. Check local regulations before travelling internationally with one.
Worth a watch: USING the STARLINK MINI for Off Grid BACKUP INTERNET & WIFI CALLING · Creating A Simpler Life Off-Grid