Short answer: for most touring setups running a fridge, lights and device charging, somewhere between 200W and 400W of solar is the sweet spot. A single fridge on a light setup can get by on ~200W; add an inverter, Starlink or a second fridge and you're looking at 300–400W or more. But "most setups" isn't your setup — so here's how to work out your actual number instead of guessing.
The rule that actually works
Solar isn't sized by the size of your battery — it's sized by how much power you use in a day. The job of your panels is to put back what you took out. So the real question isn't "how much solar do I need," it's "how much power do I use, and how much sun will I realistically get to replace it?"
The rough working is: your daily usage in watt-hours, divided by the number of genuinely useful sun hours you'll get, divided again by real-world losses. That last part is where most online calculators quietly lie to you.
The calculator does this exact working for you — punch in your fridge, lights and gear, pick your season and shade, and it sizes the panel array against your real daily draw and realistic sun, not best-case numbers.
Why a 200W panel doesn't make 200W
This is the single biggest thing people get wrong. A "200W" panel is rated in perfect lab conditions — cool temperature, direct overhead sun, clean glass, perfect angle. In the real world you lose a chunk of that to:
- Heat. Panels lose efficiency as they get hot — and a panel baking in the Aussie sun is well above its rated test temperature.
- Angle. Unless you're tilting toward the sun and adjusting through the day, a flat panel loses output morning and afternoon.
- The controller. An MPPT controller is far better than a cheap PWM one, but even MPPT has losses. Cabling and connectors take a little more.
- Cloud and shade. A thin overcast can knock output down by half or more; a tree shadow across a panel hurts far more than its size suggests.
Add it up and a "200W" panel realistically delivers more like 130–150W of useful charge on a good day, less on a poor one. Sizing as though it makes the full 200W is exactly how people end up short. Our calculator applies these derates on purpose, which is why it sometimes recommends more panel than a simpler tool.
Sun hours change everything — and they're not the same across Australia
"Peak sun hours" is the number of hours of full-strength sun you effectively get in a day. In an Aussie summer up north you might get 5–6; in a southern winter it can drop below 3. That's a near-threefold swing, and it directly changes how much panel you need. The same setup that cruises through a Queensland winter can fall behind in an overcast Victorian one.
The practical takeaway: size for the worst conditions you'll actually camp in, not the best. If you only ever tour in summer, you can run leaner. If you head out in winter or park in shade, budget for more panel — or plan to top up by driving.
We learned this the hard way on a 3-day trip in high-30s heat. The camper ran a Dometic CFX95 plus lighting off 2 × 200Ah AGMs, backed by about 250W of solar — on paper, plenty of battery. But AGM only gives you roughly half its rated capacity to use safely, and in that heat the fridge was working overtime. We spent the whole trip physically moving panels around chasing the sun, and it still wasn't enough — the array simply couldn't put back what the fridge was pulling out in that heat. Meanwhile the Dmax was running a 120Ah battery on a 60L Kings fridge, and on the morning of day 3 we woke up to find it had hit its low-voltage cutoff overnight and switched off. Nothing was wrong with the gear — it was just undersized for the conditions we were actually camping in, not the conditions the numbers assumed.
At the time the camper was running a Projecta DC-DC charger with solar input built in — one unit doing both jobs. Since then we've separated the two: a dedicated Victron SmartSolar MPPT 100/20 just for the panel, running into 2 × iTechworld iTech120X PRO lithium batteries. The folding panel earns its keep because I can angle it and move it into full sun even when the camper itself is parked in shade. A combined charger shares one output between solar and driving charge, so splitting them means the panel isn't fighting the DC-DC for the same ceiling — plus the switch to lithium alone gave us far more usable capacity than those old 200Ah AGMs ever had.
Fixed panels vs folding/portable
Roof-mounted fixed panels are simple and always working while you drive, but they're flat, they cook in the heat, and they can't move out of shade. Portable folding panels and blankets let you park the camper in shade and put the panel in the sun, and you can angle them — often making a smaller portable outperform a bigger fixed panel in practice. Many serious setups run both: fixed panels for effortless daily topping-up, plus a folding panel to chase sun when parked up for a few days.
Don't forget the alternator
Solar isn't your only charging source. If you drive between camps, a DC-DC charger tops the battery up off your alternator — and on a driving day that can do more than your panels. The two work together: solar carries you while parked, driving tops you up when you move. If you're regularly on the road, you can run less solar; if you sit in one spot for days, solar has to do all the work. Our battery and charging setup matters here as much as the panel.
Rough starting points
- Fridge, lights, phone charging, weekends: ~150–200W is often enough, especially if you drive between spots.
- Fridge + more gear, longer trips, some inverter use: 300W is a comfortable middle.
- Fridge/freezer, inverter appliances, Starlink, days parked in one spot: 400W+, and consider portable panels to chase sun.
These are starting points, not answers — your fridge size, your climate, your shade and how you travel all move the number. That's exactly what the calculator is for.
If you camp anywhere that gets genuinely hot, size for that heat specifically — not an average day. A fridge working hard in the high 30s pulls a lot more than the same fridge on a mild day, and that's exactly when solar has the least margin for error. I'd rather carry more panel than I need most trips than risk another morning finding the fridge has cut itself off.
Want your actual number instead of a rule of thumb? Put your gear, season and shade into the 12V calculator and it'll size your panel array against your real daily draw and realistic Australian sun.