How we worked this out: we took every figure in the specification table from the instruction manual supplied with the unit. Runtime estimates apply an 83 per cent conversion factor derived from the manufacturer’s own published runtimes. Appliance draws are stated so you can substitute your own.
When a storm takes out the street, two things start costing you money almost straight away. The food in the fridge begins its slow walk towards the bin, and the internet drops out even though the NBN network itself is perfectly healthy. A portable power station solves both, but only if you buy enough capacity, and the number printed on the box is not the number that reaches your appliances.
This guide works through the arithmetic using the instruction manuals for three VoltX units sold in Australia. Every assumption is stated so you can rerun the sums against your own fridge.
Key takeaways:
- A 1152Wh station typically carries a modern fridge plus modem and router for 12 to 16 hours.
- A 2240Wh station stretches the same load to roughly a full day.
- A 307Wh station is a comms and devices unit. It will not hold a fridge overnight.
- Expect 83 to 85 per cent of rated capacity to reach your appliances.
- Only one of the three units documents automatic switchover, at 20ms.
Why Your Internet Dies Before Your Fridge Does
Fibre and HFC connections terminate at a powered box inside the house, usually an optical network terminal, which feeds a mains-powered modem and router. When the street loses power, all three go dark. The fault is not in the network. It is on your wall.
Battery backup for the optical network terminal was dropped as standard equipment years ago, so most households have nothing holding the connection up. The good news is that comms gear is cheap to run. A modem, a router, and an optical network terminal together draw between 10W and 20W. Your fridge is the expensive guest at the party.
» MORE: Compare portable power stations by capacity and output
The Only Number That Matters: Usable Watt-Hours
A watt-hour is one watt drawn for one hour. A 1152Wh battery holds 1152 watt-hours, so a 100W load gives roughly 11.5 hours in theory.
In practice, you never get the full figure. Converting stored DC into 240V AC costs energy, the fan draws a little, and the battery management system holds back a reserve. The manufacturer data shows the size of that loss. The Outbax VoltX M2400 manual rates the unit at 2240Wh and quotes 29 hours for a 65W car refrigerator. But 2240 divided by 65 is 34.5 hours, so the quoted figure is about 84 per cent of rated capacity. The same manual quotes 17 hours for a 110W television, which works out at 83 per cent, and 31 charges of a 60Wh laptop, which lands in the same place.
Here’s what one of our customers said about the VoltX M2400 Portable Outbax Power Station:
“Was very pleased with the product, and will be of great use on our travels.”
Three appliances, three independent figures, all clustering around 83 to 85 per cent. So size a unit by taking rated capacity, multiplying by 0.83, and dividing by your appliance draw.
Technical Specifications Compared
The table below is drawn directly from the instruction manuals supplied with each unit. Nothing here is estimated except the usable energy row, which applies the 83 per cent factor explained above.
| Specification | VoltX E600 | VoltX Topband V1200 | VoltX M2400 |
|---|---|---|---|
| Rated capacity | 307.2Wh | 1152Wh (25.6V / 45Ah) | 2240Wh (50000mAh / 44.8V) |
| Usable energy at 83 per cent | approx. 255Wh | approx. 956Wh | approx. 1859Wh |
| Battery chemistry | LiFePO4 | LiFePO4 | LiFePO4 |
| Rated charge cycles | 3000 | 4000+ | 4000 |
| AC output | 600W continuous, 1200W peak | 1200W continuous, 2400W peak | 2400W continuous, 4800W peak |
| Output waveform | Pure sine wave, 240V / 50Hz | Pure sine wave, 200 to 240VAC, 50/60Hz | Pure sine wave, 100 to 240V by region |
| UPS switchover | Not documented | Within 20ms | Not documented |
| Solar input | Supported, 3 to 4 h full charge | XT60, 11.5V to 55V, 550W max. | XT60 600W x 2, 12V to 59V |
| AC recharge | 5 to 6 h at 60W, 3 to 4 h at 96W | 700W max. input | 2000W max. input |
| USB-C output | PD 60W | PD 100W | PD 100W plus PD 45W |
| 12V jump start | 500A start, 1000A peak | Not fitted | Not fitted |
| Weight | 7kg | 13kg | 26.8kg |
| Dimensions (mm) | 283 x 221 x 215.8 | 365.4 x 235 x 274.5 | 409 x 298 x 310 |
| Operating temperature | minus 20°C to 55°C | 0°C - 45°C | minus 10°C to 40°C |
| Charging temperature | 0°C to 55°C | -5°C - 40°C | 0°C to 40°C |
| Warranty | 24 months | 24 months | 24 months |
Source: instruction manuals supplied for the VoltX E600, VoltX Topband V1200 and VoltX M2400. Manual references PB-20E, V1200 and S2200Pro respectively. AC output specifications are configured by region; the figures shown are the 240V Australian configuration, as stated in the manual.
How Long Will a Power Station Run a Fridge?
What Your Fridge Actually Consumes
Fridges do not draw their nameplate wattage continuously. A typical Australian 400L fridge freezer uses between 1.2kWh and 2.0kWh per day depending on age, size, and ambient temperature. The compressor pulls perhaps 150W while running, but it runs maybe a third of the time. Averaged out, that is 50W to 85W, not 150W.
Using the 83 per cent figure, a VoltX Topband V1200 delivers about 956Wh of real energy. Against an efficient modern fridge averaging 54W, that is roughly 17 hours. Against a tired 20-year-old unit averaging 85W, that’s closer to 11 hours. A VoltX M2400 delivers about 1859Wh, or 22 to 34 hours on the same two fridges.
Why Camping Fridges Change the Maths
Plenty of Australian households already own a compressor camping fridge, and in a blackout it is the smarter appliance to run. The M2400 manual quotes 29 hours for a 65W car refrigerator, assuming continuous draw. A real camping fridge cycles, so expect longer. Shifting perishables into it and leaving the big fridge shut is the most effective move available during a long outage.
Fridge and Modem Together
Add 15W of comms gear to a 54W fridge, and you are drawing 69W. A V1200 covers that for about 14 hours, which is enough for a night. An M2400 covers about 27 hours. An Outbax VoltX E600 power station at 307.2Wh delivers around 255Wh, under five hours on the same load.
How Long Will It Keep the NBN Modem and Wi-Fi Running?
Far longer than most people expect, because the loads are tiny. Assume 15W for an optical network terminal, a modem and a router running together. The VoltX E600 holds that for roughly 17 hours, the VoltX Topband V1200 for around 63 hours, and the VoltX M2400 for about five days.
Here’s what one of our customers said about the VoltX Topband V1200 Power Station:
“Great little unit, I mainly use it to run a portable freezer, camp lights and sundry stuff, also take my electric guitar and amp down the beach occasionally so I can turn it UP ha ha. It runs all my power tools. Lasts about 30 hrs to almost total flat just running freezer (40w draw when running), but I recharge when around 5% - 10% with AC around 24 hrs I haven’t set up or tried any solar input yet, but it’s coming. I also recently bought the Gentrax 800 generator mostly for backup to charge the station, which takes about 2 hours as with home AC. Cheers.”
If connectivity is your only concern, you do not need a large unit. An E600 with a 600W continuous AC output and a 10W LED work light will keep a household online and charge phones and laptops. Outbax stocks the full range, and for a comms-only brief the smallest tier is the right buy.
» MORE: VoltX E600 307Wh portable power station review
What Power Station Size Do You Need?
- Comms and devices only, 300Wh to 600Wh. The VoltX E600 at 307.2Wh is perfect for this and can keep a modem, router, phones, and laptops running for a day or more.
- Overnight fridge plus comms, 1100Wh to 1900Wh. The VoltX Topband V1200 at 1152Wh is the natural pick. The VoltX V1800 and the ACE 2000W 1920Wh unit suit households with a second fridge or a chest freezer.
- A full day or more, 2000Wh and above. The VoltX M2400 at 2240Wh, with 2400W continuous output, is one of your top choices; enough for a fridge, comms, lighting, and a kettle, though not all at once.
To size it yourself: take your fridge’s annual kWh rating from the energy label, divide by 365, add roughly 0.4kWh for comms and lights, then divide the result by 0.83.
What a Portable Power Station Will Not Do
This is the part most retailers leave out, and the part that stops people buying the wrong thing.
Switchover Is Not Instant, and Most Units Have None at All
Of the three manuals reviewed, only the V1200 documents a UPS function. It states that when the grid is suddenly cut, the unit switches to battery mode within 20ms. The same manual is blunt about the limits, calling it a non-professional UPS function that doesn’t support time switching and advising against connecting equipment that requires a high uninterruptible power supply, such as data servers and workstations.
Twenty milliseconds is fine for a fridge and a modem. It is not a guarantee for a desktop PC, a NAS, or medical equipment. For those, buy a dedicated UPS and use the power station to keep it topped up.
High-Power Appliances to Avoid
Ducted air conditioning, electric hot water, and electric cooktops are out of reach. A 2400W output sounds generous until a 2200W kettle and a 1200W hair dryer meet it at once. The M2400 manual quotes 1.6 hours for a 1200W hair dryer and 1.2 hours for a 1500W oven. These are short bursts, not sustained service.
Four Ways To Stretch The Hours You Have
- Pre-cool before the outage. If a storm warning is up, turn the fridge down and freeze water bottles. Thermal mass is free storage.
- Keep the door shut. A full fridge holds temperature for four to six hours unopened.
- Add solar. The V1200 accepts up to 550W through its XT60 input; the M2400 has two 600W inputs. On a clear day, that replaces most of a night’s consumption.
- Shed idle loads. Switch off the AC output when nothing is plugged in. Both units have idle standby timers for this.
Storage and Safe Operation
Keep the unit upright, off the floor, out of direct sun, and clear of anything that could block the fan. The M2400 charges between 0°C and 40°C and operates between minus 10°C and 40°C, so a closed car in a Queensland summer is the wrong place for it.
Recharge an emergency unit every three to six months and store it part charged rather than flat. Leaving a battery empty for a year is the most common reason a backup fails the night you need it. Outbax publishes placement and storage guidance on its power stations collection, and it applies at home as it does at a campsite.
The Short Version
Size the unit to the job, not to the badge. For comms alone, 300Wh is plenty. For a fridge and your internet through one night, 1152Wh is the realistic floor. For a full day with room to spare, 2240Wh. Multiply the rated capacity by 0.83, divide by your actual draw, and you will know before you buy, not after.
Whichever unit you choose, charge it today. Outbax carries the full range of capacities covered here, and the best time to find out your backup is flat is not at 9 pm in a thunderstorm. Browse through our collection and find the perfect fit for your backup needs.
