What Does 850W Solar Really Produce on a Caravan Roof?
Our real world results from our 23ft caravan running 300Ah lithium, Starlink, a compressor fridge and everyday camp life.
Most solar articles will tell you that an 850W solar system should produce massive numbers on a sunny day. On paper, that's true. In the real world, things are rarely that simple.
After months of travelling, monitoring our battery system and paying close attention to what actually goes in and out of the batteries each day, we've learned that solar performance on a caravan roof can look very different from the figures people calculate online.
Here's what we've found from our own setup.
Our Setup
For context, this isn't a small weekend camping rig.
We're travelling in our 2022 Olympic Javelin X8 23ft caravan fitted with:
- 850W of roof mounted solar
- 3 x 100Ah lithium batteries (300Ah total)
- Projecta PM435C battery management system
- Projecta DMS30 charger
- Starlink Mini
- Compressor fridge
- TV / Stereo
- Sirocco fans
- Lighting, phone charging and normal day to day caravan use
The system is used exactly as we travel.
We're not switching everything off just to post impressive battery numbers on socials.
We built the system to enjoy travelling comfortably.
The Biggest Surprise
When we first looked at the theoretical output of an 850W solar system, we expected to see significantly higher charging figures than we were getting.
Instead, the numbers on the battery monitor told a different story.
These days, our system typically produces around 20 amps during good daylight conditions, with peak outputs regularly reaching 24-25 amps under favourable conditions.
That's a lot better than some of the lower figures we saw earlier on, but it's still nowhere near what many people expect when they hear "850 watts of solar."
And that's where real world experience becomes more valuable than a spreadsheet.
The Two Panels That Barely Contribute
One discovery was particularly interesting.
Our system includes two older 170W solar panels that remained on the roof from a previous configuration.
Combined, those two panels generally contribute only around 4-6 amps under good conditions.
While they still contribute useful power, they're clearly not producing anything close to what many people would expect from 340W of solar from factory.
That observation sent us looking elsewhere for possible limitations in the system.
Where We Think The Real Bottleneck Is
Our current theory is that wiring losses play a bigger role than most caravan owners realise.
It's easy to focus on panel wattage because that's the number everyone talks about.
But solar power still has to travel from the roof to the charger.
Cable length, cable size, connectors, joins and installation quality all affect what eventually reaches the batteries.
We're continuing to monitor the system, but at this stage we strongly suspect that losses between the panels and charging equipment are limiting overall performance.
It's a reminder that buying more solar panels isn't always the answer.
Sometimes the rest of the system matters just as much.
What The System Actually Does Well
Despite not producing the theoretical numbers many people expect, the system still performs extremely well in day to day use.
One evening we started with the battery bank sitting at 98%.
Overnight we used:
- Starlink Mini
- Television / Stereo
- Interior lighting
- Phone charging
- Multiple Sirocco fans
- General evening power consumption
The following morning the batteries were sitting at approximately 73%.
That's a 25% overnight reduction while actually living in the caravan, not trying to conserve every amp-hour.
For a 300Ah lithium battery bank, that's completely manageable and gives us confidence when free camping (which we absolutely prefer over caravan parks, but thats a different story).
The Starlink Reality
One of the biggest power users in our overnight setup is Starlink Mini.
When we originally ran Starlink from the vehicle's auxiliary battery, we noticed the battery was taking a much bigger hit overnight than expected.
Once we started tracking our power usage more closely, it became obvious why.
Starlink draws power continuously, whether you're actively using the internet or not.
One thing we've learned is that Starlink isn't necessarily a problem, it's simply a load that needs to be accounted for.
If you're trying to stretch battery capacity during poor weather or extended periods without decent solar input, switching Starlink off when it's not being used can make a noticeable difference.
In our case, we generally leave it running. Our 300Ah lithium bank and solar setup comfortably support our lifestyle, so the convenience outweighs the power savings.
However, for travellers with smaller battery banks, Starlink can easily become one of the larger overnight power consumers in the system.
The important thing isn't avoiding Starlink.
It's understanding the impact it has on your daily power budget.
What We'd Tell Someone Building A System Today
If you're planning a caravan power system based purely on advertised solar figures, leave yourself some margin.
A lot of margin.
Real world conditions rarely match laboratory conditions.
Shade, cloud cover, heat, panel angle, wiring losses and charging limitations all affect performance.
Our experience has shown that battery storage is often more important than chasing another few hundred watts of solar.
Solar replaces what you've used.
Battery capacity determines how comfortably you can live overnight.
The combination of 300Ah lithium storage and 850W of solar has proven to be a practical balance for the way we travel.
Final Thoughts
The biggest lesson from our setup isn't that solar ratings are wrong.
It's that real world camping conditions don't behave like a product brochure.
Our 850W solar system typically produces around 20 amps during good daylight conditions and regularly peaks at 24-25 amps.
While those numbers may be lower than theoretical calculations suggest, they've proven more than capable of supporting our day to day lifestyle when paired with 300Ah of lithium storage.
We've run Starlink, fans, television, lighting, device charging and all the normal comforts of caravan life without needing to obsess over every amp hour.
If there's one takeaway from our experience, it's this:
Don't design your system around perfect conditions.
Design it around how you actually travel.
That's where the real answers are found.
Written by Zak Noffke - Online Store Manager at 4x4 & Outdoor.
Full time caravanner currently travelling Australia in a 2022 Olympic Javelin X8 and 200 Series LandCruiser.
