Motorhome solar power gets sold as a magic fix. Stick a panel on the roof, forget about electricity, live off grid forever. I believed a version of that too before I actually had to rely on a system through a proper stretch of wild camping and cheap overnight stops rather than hookup pitches. The reality is more nuanced, and a lot of people spend money on the wrong part of the system.
I have now run two different setups across the Elddis Autoquest and the current Swift KonTiki 774, and the lessons from getting it wrong the first time round are worth more than anything in a dealer brochure. So here is what I have actually learned about solar, batteries and keeping the lights on when you are away from a hookup point.
The battery matters more than the solar panel
This is the bit nobody tells you when you are looking at panels. The solar panel is just the thing that puts energy in. The battery is what determines how much you can actually use, and how reliably. If your battery is small or old, a bigger panel will not save you. I ran lead acid leisure batteries for years without really understanding what I was losing. Lead acid batteries genuinely give you about half their rated capacity if you want them to last. Drain them further and you will kill them early. So a 100 amp hour lead acid battery is really giving you fifty amp hours of usable power, and you would not know that from the sticker.
Lithium changed the equation completely for me. A lithium battery gives you close to its full rated capacity usably, charges faster, weighs a fraction of the equivalent lead acid unit and lasts vastly more charge cycles. It costs more upfront, no question. But when I actually worked out the cost per usable amp hour over the life of the battery, lithium won comfortably. I switched during the upgrade to the KonTiki and have not looked back.
How much solar you actually need
The panel size question depends entirely on what you are running and when. This is where most people either overspend on panels they do not need or underspend and end up disappointed. If you are running lights, a water pump, charging phones and running a fridge on gas, a modest panel setup keeps a decent lithium battery topped up through most of the year in the UK. Once you start adding an inverter for laptops, a compressor fridge, or serious Starlink use like I wrote about in my Starlink motorhome review, your daily consumption goes up meaningfully and the panel needs to work harder to keep pace.
The other factor people underestimate is winter. Solar output in the UK between November and February is a fraction of what you get in summer, through a combination of shorter days, lower sun angle and more cloud cover. If you are planning serious off grid time in winter, do not size your system based on a sunny July afternoon. Size it for the worst case, or accept you will need to run the engine or a generator to top up on the darkest days.
The mistakes I made the first time round
My first setup on the Elddis was underspecified in almost every direction. Small panel, ageing lead acid battery, no proper battery monitor. I had no real visibility into what state of charge I was actually at, which meant I either ran things too cautiously out of fear of flattening the battery, or occasionally got caught out entirely with nothing left in the tank.
A proper battery monitor is not a luxury item. It is the single cheapest upgrade that changes how you use a motorhome off grid, because it turns guesswork into an actual number you can plan around. I would put this above upgrading the panel itself if you are working with a limited budget and have to choose one improvement.
The second mistake was ignoring the charge controller. A cheap PWM controller does the basic job but is meaningfully less efficient than an MPPT controller, particularly on cloudy days or with panels not perfectly angled to the sun. When I upgraded to MPPT alongside the lithium battery, the difference in how much of the panel's potential actually reached the battery was obvious within days.
What I actually run on the KonTiki now
The current setup is lithium leisure batteries, an MPPT controller and a solar array sized generously enough that in spring through autumn I rarely think about power at all. Combined with the fixed underfloor garage storage I talked about in my Swift KonTiki 774 review, there is enough capacity to run the fridge, charge laptops, run Starlink for a full working day and still have headroom in the evening.
Winter is the exception. In deep winter I plan trips more carefully around hookup availability or accept shorter off grid stretches, because no amount of panel is going to fully offset a grey December day in the UK. That is simply physics, not a setup failure, and I would be suspicious of anyone claiming otherwise.
Do you actually need all of this
Honestly, no. If you are doing occasional weekends on serviced campsites with hookup, a basic setup is entirely fine and you should not spend money chasing a spec you will never need. The investment in proper lithium, MPPT and generous solar only pays off if you are genuinely spending significant time off grid, wild camping, or working remotely from the van for extended periods the way I do.
Match the system to how you actually use the motorhome, not to what forum enthusiasts tell you that you need. That is the single biggest lesson from getting this wrong once already.
The bit that actually matters most
If I had to boil this whole post down to one piece of advice, it would be this. Buy the best battery you can afford before you worry about the panel. A good lithium battery with modest solar and a proper monitor will serve you far better than an enormous panel bolted to a tired lead acid battery with no visibility into what state it is in. Get that foundation right first, and everything else about running a motorhome off grid gets considerably easier.
