Portable power stations

1Start here: does your van already cover it?

Before you spend anything, look at what the van already carries. Some vans already carry enough battery and solar to make a power station a duplicate.

As a sense of scale, a typical roof array runs around 600W and the biggest reach 3,000W. A typical battery bank is about 300Ah, which is roughly 3,600Wh of nameplate energy at 12V. These are typical figures across the vans on our site that publish them.

Compare that 3,600Wh with the watt-hour figure on any power station you are shown.

The inverter decides what 240V gear a van can run

A big battery and a big roof array still tell you nothing about whether a van can run a 240V appliance. That job belongs to the inverter, and its continuous rating decides what 240V gear a van can run. Ask for the figure when a listing leaves it out.

A van can carry 300Ah and a big roof array and still have no way to run a 240V appliance, and the brochure often won't say either way. Ask the dealer, in writing, before you assume.

This is the case for a portable unit. It arrives with its own inverter and its own outlets, so it sidesteps a specification that is often hard to pin down from a brochure, even when the van has enough battery.

Plenty of vans are set up for powered sites, with battery banks under 200Ah. Their owners are the ones a power station suits best.

2What the numbers on the box mean

Four specifications decide whether a unit suits you. The marketing usually leads with the first one alone.

Capacity, in watt-hours

Watt-hours (Wh) are how much energy the unit holds. This is the number to compare across brands, and it is the one to convert your caravan battery into as well: watt-hours are roughly amp-hours multiplied by volts, so a 100Ah battery at 12V is about 1,200Wh on paper.

You will not get all of it. Between the depth of discharge the maker recommends and the losses in converting battery power to 240V, planning on roughly 85% of the rated figure is the sensible habit. That is a rule of thumb drawn from typical manufacturer guidance. Check your own unit's manual before leaning on it.

Continuous output, in watts

Capacity tells you how long a unit lasts. Continuous output tells you what you can plug in. A big battery with a small inverter still will not run a kettle. If you choose on capacity alone, the output rating can still stop you running the kettle.

Add up what you would run at the same time, in watts, and make sure the continuous rating clears it with room to spare.

Surge rating

Motors and compressors draw far more on startup than they do once running. The surge (or peak) rating is what covers that moment. A unit whose continuous rating looks fine can still trip when the fridge compressor or a power tool kicks in, so check both figures.

Chemistry and cycle life

Most current units use LiFePO4 cells, and the good ones publish a cycle rating: how many charge and discharge cycles before the battery drops to a stated share of its original capacity. A unit rated for a few thousand cycles is in a different class from one rated for a few hundred, and that difference matters far more over ten years of trips than a small gap in capacity.

If a spec sheet does not mention chemistry or cycle life, ask the seller for both figures before you compare on price.

3How to size one

Work out what you use in a day, then buy enough for the number of days you want between charges. Count every appliance in the daily figure, because an undercount leaves you short.

Step one: your daily watt-hours

For each appliance, find the wattage on its compliance label, then estimate the hours a day it actually draws power. Multiply the two. Things that cycle on and off, like a fridge, do not run continuously, which is where most estimates go wrong in the optimistic direction.

A worked example, with every assumption stated because they are all assumptions:

The spread is the fridge's duty cycle, which the weather decides, and it's the same band our power calculator prints for these inputs. Your fridge, your weather and your habits move the figure, so run the sum with your own numbers instead of borrowing a total.

Step two: multiply by your days, then add the losses

Two nights at 600 to 780Wh is 1,200 to 1,560Wh of demand. Allowing for that 85% usable habit, you are shopping for something rated around 1,400 to 1,850Wh, not 1,200Wh. Round up, because overcast days are when you need the extra.

If a decent roof array is topping the unit up each day, the same box stretches much further. That is why the charging section below matters as much as the capacity.

Step three: the three size classes

In practice the market sorts into three bands, and once you have your daily figure you will know which one you are in.

• Around 500Wh. Devices, lights, a CPAP for a night, topping up a fridge that is mostly running off the van. A weekend unit. Light enough to carry one-handed.
• Around 1,000Wh to 1,500Wh. The mainstay. Covers the worked example above for two days or so without solar, and runs a fridge plus devices comfortably with a panel attached.
• 2,000Wh and up. Extended stays, higher-draw appliances, or running a fridge without relying on sunshine. Heavier, and the weight comes out of your payload.

4Power station, generator, or more battery in the van?

Each of these three does a different job. We earn nothing here from a generator or from more battery in the van.

A portable power station wins when

You want no installer and no holes in the van. You want the same unit to work at a picnic table, in the tent, and in the house when the power goes out. You want it to come with you to the next van. And you need 240V outlets that your van may not be able to give you, which as noted above you often cannot confirm from a spec sheet.

A generator wins when

You need to make power rather than store it. A generator keeps going as long as you keep feeding it, which no battery does. That suits long stays in poor weather and high-draw appliances.

The costs are noise, fuel and servicing, and not every camp allows one. Many caravan parks and campgrounds restrict when generators may run, and some prohibit them, so check the rules for where you are going rather than assuming.

More battery in the van wins when

You are staying with this van, you already have an inverter, and you want the cheapest usable watt-hours. Installed capacity charges itself off the roof and the car while you drive, takes up no floor space, and does not need lifting. Per watt-hour it is usually the better buy.

The tradeoffs are that it costs installation, it needs a licensed electrician, it stays with the van when you sell it, and it does nothing for you at the beach or during a blackout at home.

5When not to buy one

A power station is poor value in these four situations.

• You stay on powered sites. If your travel is park to park with a 240V post at every stop, a power station costs a lot for a backup you will rarely use. A decent extension lead and a surge protector cover you.
• Your van already has installed lithium and an inverter. You would be buying a second, smaller version of what you own. Confirm what is fitted first, in writing from the dealer, rather than relying on the spec sheet alone.
• You want off-grid air conditioning. This is the most common disappointment. A rooftop unit draws heavily on startup and then keeps drawing, so a portable box that technically starts it can still be flat well before you are comfortable. If this is the goal, you want a properly specified installed system or a powered site, not a box.
• Your payload is already tight. A big unit is serious weight, and it competes with water, gear and everything else in your allowance. Check the unit's published weight against what you actually have spare. If you do not know your spare payload, work it out before you shop.

6Keeping it charged

How you top it up decides whether the capacity you bought is enough.

From mains. Fastest, and the one to use the night before you leave. Check how long a full charge takes, because it varies enormously between units.

From the car while driving. Useful on travel days, usually slow through a 12V accessory socket. If you move every day or two, this alone can keep a smaller unit charged.

From a portable solar panel. The one that changes the maths for stationary camping. A folding panel plugged straight into the unit adds daily energy without touching the van, and it is the difference between a box that lasts two days and one that lasts as long as the weather holds. Match the panel to the unit's stated input limit and connector rather than buying on wattage alone.

7What to check on any brand's spec sheet

Take this list to whichever brand you are looking at. Ask the seller for any figure the spec sheet leaves out.

• Capacity in watt-hours, stated plainly. Amp-hours at an unstated voltage hides the real size.
• Continuous output in watts, and the surge rating as a separate figure.
• Cell chemistry and a cycle rating with the capacity level it is measured to.
• Maximum solar input and the connector type, so a panel you buy later actually fits.
• Weight, because it lands in your payload.
• Australian warranty terms and the length, from an entity you can contact here.
• Local support and spare parts. A cheap unit with no local service is hard to get fixed.

8Common questions