How Much Solar Power Do You Need for a 4WD Touring Setup?

How Much Solar Power Do You Need for a 4WD Touring Setup?

"How much solar do I need?" is one of the most common questions in 4WD touring, and it's also one of the most commonly answered with a generic number that has nothing to do with the person asking. A 100W panel might be plenty for a weekend camper running a small fridge and a couple of lights. The same panel won't come close to covering a full touring rig running a fridge, lighting, USB charging, a water pump, and a laptop or Starlink setup, especially through a run of overcast days in southern states over winter.

The right answer comes from working backwards from what you're actually running, not forwards from a panel size that sounded reasonable in a forum post.

Step 1: Work Out What You're Actually Drawing Each Day

Before sizing solar, you need a realistic daily power budget in amp-hours (Ah), since that's the unit both your battery capacity and your solar output are measured in.

Common touring loads and roughly what they draw over a day:

  • Compressor fridge (40–60L): typically the single biggest draw in most setups, often in the range of 20–40Ah per day depending on ambient temperature, how often it's opened, and how well it's insulated from cabin or engine bay heat.

  • LED lighting: genuinely minor, usually just a few Ah per day even with several lights running for hours.

  • USB charging and 12V accessories: small individually, but it adds up across phones, cameras, headlamps, and other devices.

  • Water pump: brief, high current draws, but low total Ah over a day unless you're running it constantly.

  • Inverter loads (laptop charging, CPAP, camera battery chargers): can be a meaningful addition, particularly anything that needs to run overnight.

Add these up honestly, including a buffer for things you'll forget to account for, and you'll usually land somewhere between 40 and 100Ah per day for a genuine touring setup, with fridge-heavy, high-accessory rigs sitting at the top end of that range.

Step 2: Size Your Battery Before You Size Your Solar

Solar panels charge a battery, they don't power your gear directly in any meaningful sense once the sun goes down or the sky clouds over. That means battery capacity comes first in the sizing conversation, solar exists to keep that battery topped up.

A few things worth getting right here:

  • Lithium (LiFePO4) batteries have largely replaced AGM in touring setups, offering more usable capacity for the same physical size and weight, since they can be discharged much deeper without damage.

  • Size your battery for at least a couple of days of typical use without any charging input at all, covering an overcast stretch or a day spent stationary at camp without driving.

  • A 100–200Ah lithium battery is a common range for a genuine touring fridge-and-accessories setup, with the exact number depending on your daily draw from Step 1 and how many buffer days you want built in.

Undersizing the battery is a common mistake that no amount of solar panel wattage will fix, if there's nowhere to store the power, extra panel capacity is largely wasted.

Step 3: Match Solar Output to Your Daily Draw

This is where the actual "how much solar" question gets answered, and the honest answer is that panel wattage alone doesn't tell the whole story. What matters is realistic daily output, which depends on panel size, sun hours, angle, shading, and weather, not just the number printed on the panel.

As a rough general guide for planning purposes:

  • A well-positioned 160–200W panel can produce a meaningful contribution toward a 40–60Ah daily draw on a genuinely sunny day with good sun hours.

  • Cloud cover, poor panel angle, shading from trees or the vehicle itself, and shorter winter days in southern states can reduce that output substantially, sometimes by half or more.

  • Fridge-heavy, high-draw setups in the 70–100Ah/day range typically need either a larger panel array, a combination of fixed roof panels and a portable folding panel for flexible positioning, or meaningful support from driving time via a DC-DC charger.

Treat solar as one input into your charging system, not the whole solution, particularly for touring through forested, gorge, or consistently overcast country where panel output can be genuinely unreliable for days at a time.

Step 4: Don't Rely on Solar Alone, Pair It With a DC-DC Charger

A DC-DC charger draws power from your alternator while you're driving and charges your auxiliary battery properly, separately from your vehicle's starter battery. For most touring setups, this does more heavy lifting than people expect, especially on trips with solid daily driving distances, since a few hours behind the wheel can recover a significant chunk of overnight fridge use regardless of what the sky is doing.

Solar and a DC-DC charger complement each other well: the DC-DC charger handles charging while you're driving, and solar keeps the battery topped up while you're stationary at camp, particularly useful on multi-day stops where you're not driving enough to rely on the alternator alone.

Fixed Roof Panels vs Portable Folding Panels

Both have a place in a touring setup, and plenty of serious tourers run both.

Fixed roof-mounted panels charge automatically while driving and while parked, without any setup effort, but they're stuck at whatever angle your roof happens to be, which isn't always optimal, and they can't be moved into a sunny patch if your camp spot is shaded.

Portable folding panels can be positioned for the best angle and moved to chase the sun throughout the day, which often means genuinely better output per watt than a fixed panel in the same conditions, but they need to be set up, watched, and packed away, and they're vulnerable to theft if left unattended at a remote camp.

A combination, a smaller fixed panel for passive charging plus a portable panel for camp days, gives the most flexibility for a genuine touring setup that spends real time both driving and stationary.

A Realistic Example

For a typical touring setup running a 50L fridge, LED lighting, USB charging, and occasional inverter use, drawing somewhere around 50–60Ah per day:

  • A 100–150Ah lithium battery gives a reasonable buffer for a day or two without charging input

  • A 160–200W solar setup, ideally with the flexibility of a portable panel for camp days, covers a meaningful share of daily use in good conditions

  • A DC-DC charger picks up the rest during driving days, which for most touring itineraries make up the majority of the trip

This isn't a one-size-fits-all number, it's a starting point to adjust against your actual fridge size, accessory list, and the kind of country you're touring through.

Get the Sizing Right Before You Buy

The most expensive mistake in solar sizing isn't buying too small a panel, it's building a whole electrical system around a guess rather than an actual daily power budget. Work out your realistic Ah draw first, size the battery to cover a couple of buffer days, then size solar and your charging setup to keep that battery topped up, in that order.

At Track Auto, we work with 70, 75, and 79 Series owners building out genuine touring rigs, and getting the electrical system right is as much a part of a solid build as the panels, guards, and chassis components we supply. If you're planning a touring setup and want it built around your actual gear rather than a generic package, that's exactly the kind of build we help owners get right.

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