Short answer: a fixed panel on the roof charges every time the sun's on it, including while you drive, and you never set it up. A folding panel or blanket goes out in the sun while the vehicle sits in the shade, and you can move it as the sun moves. Lots of touring setups end up with both: a fixed panel on the roof and a portable one as a top-up. Which to start with comes down to roof space, weight and whether you park in the shade.
How do they compare?
| Fixed (glass, framed) | Folding (glass, briefcase) | Blanket | Flexible (glass-free, stuck or screwed down) | |
|---|---|---|---|---|
| Example | Exotronic 130W Fusion | Exotronic 200W folding | Exotronic 200W Fusion blanket | Sunman eArc 175W |
| Weight (maker's figure) | 6.30 kg | 11.2 kg | 5.6 kg | 3 kg |
| Weight per 100 W (our arithmetic) | About 4.8 kg | 5.6 kg | 2.8 kg | About 1.7 kg |
| Charges while driving | Yes | No | No | Yes |
| Can chase the sun | No | Yes | Yes | No |
| Controller included | n/a | No | No | n/a |
Should I get a fixed roof panel?
If you have the roof space, it's the one that works without you thinking about it. It's charging on the drive in, while you're at the servo, and all day at camp.
Exotronic's 130W Fusion fixed panel as an example:
- 900 x 670 x 25 mm, 6.30 kg, 36 cells.
- 3.2 mm tempered glass on a 25 mm anodised aluminium frame, rated for wind loads up to 2400 Pa and snow loads up to 5400 Pa.
- A fully potted IP68 junction box and an 800 mm fly lead.
- Electrical: Vmp 21.6 V, Imp 6.02 A, Voc 25.2 V, Isc 6.6 A.
The catch: it's only in the sun when the vehicle is. Park under a tree on a hot day and the roof panel is in the shade with you.
Does a fixed panel need an air gap?
Yes, airflow behind the panel matters. With a fully insulated back, Victron say cell temperature can routinely go over 100 °C, and hotter panels make less power. Exotronic list their panels at -0.37% per °C above 25 °C. So, as an example, a panel running at 65 °C (40 °C over) is down by about 40 x 0.37 = 15%.
Exotronic's warranty terms ask for suitable separation, ventilation and mounting for the installation. Mount it on proper solar mounting brackets rather than flat against the roof.
Is a folding panel worth it?
It suits anyone who parks in the shade, or who's out of roof space. You park where it's cool and put the panel where the sun is.
Exotronic's 200W portable folding panel (the no-controller version):
- 11.2 kg, folding to 780 x 670 x 40 mm; open, it's 780 x 1350 x 19 mm.
- Two 100 W halves wired independently, so it keeps working if one side is shaded.
- 3.2 mm tempered glass, anodised aluminium frame, IP65/IP67 junction box, fold-away legs, corner bumpers and a padded canvas bag.
- Cells vs panel: the cells are 23% efficient; the whole panel is 19.3%. When comparing panels, compare like with like: don't put one panel's cell figure against another's panel figure.
- Electrical (both halves together): Vmp 19.8 V, Imp 10.12 A, Voc 24.1 V, Isc 10.5 A.
- A 5 m cable from MC4 to a 50 A grey Anderson plug, and two 50 A grey Anderson tails for your controller. What the colours mean is in our Anderson plugs guide.
No controller is included. Always put a solar charge controller between the panel and the battery to prevent overcharging.
The trade-off is weight and bulk. At 11.2 kg it's the heaviest per watt of the four here, and it has to be set up, turned, packed away and kept an eye on at a busy campground.
What about a solar blanket?
Same job as a folding panel, at half the weight for the same watts, and it packs much smaller.
Exotronic's 200W Fusion folding solar blanket:
- 5.6 kg, folding to 430 x 300 x 80 mm; open, 1270 x 1130 mm.
- 25.6% efficient N-Type TOPCon cells under an ETFE surface.
- Reinforced eyelets to peg it down or hang it, so it's easy to move through the day.
- Electrical: Vmp 18.5 V, Imp 10.81 A, Voc 21.6 V, Isc 12.1 A.
- A 5 m extension cable with 50 A grey Anderson-style plugs. No charge controller included.
Against a folding glass panel: much lighter and smaller, but no glass front and no stand, so it lies on the ground or hangs from something. Lay it on a hot bonnet or a dark tarp and remember the airflow point above.
And glass-free flexible panels?
These sit in between: fixed to the vehicle like a roof panel, but very light. Sunman's eArc panels are glass-free, 2.8 kg per square metre and 2 mm thick. Their 175 W off-grid model weighs 3 kg, which Sunman put at 70% lighter than conventional glass modules. We stock the Sunman eArc 175W and others in the range.
They fix on with screws and adhesive, and the details matter, because a flexible panel glued flat to a roof has nowhere for its heat to go. From the makers' instructions:
- Leave a gap. Exotronic's flexible panel guide says panels can heat above 85 °C in use, and with silicone adhesive you need a 2-5 mm gap between the panel and the roof, using a spacer or their 2.3 mm or 4.6 mm VHB tape.
- Don't seal the edges. It traps air under the panel, which expands as it heats and can damage both the panel and the roof.
- Use the right glue. Silicone-based (SG20, Fix8) is suitable; polyurethane (Sikaflex) isn't.
- Leave it alone after. Sunman say don't disturb the panel or the adhesive for at least 24 hours, and leave at least 5 mm between modules.
- Bending: Sunman's manual says don't bend the module during installation; Exotronic's guide allows a gentle curve (about 100 mm mid-point over 1.5 m, one axis only). Follow the maker of the panel you're actually fitting.
On the heat: using Exotronic's -0.37% per °C, a panel at 85 °C is 60 °C above 25 °C, so roughly 22% down on its rating. It's an example, but it shows why the gap is worth the effort.
So which should I get?
- Mostly driving, short stops, or you want set-and-forget: a fixed panel on the roof.
- You park in the shade, or the roof is full: a folding panel or blanket. Blanket if weight and space matter more than a glass front and legs.
- Weight is everything (a pop-top or a canopy): a glass-free flexible panel, fitted the way its maker says.
- Most touring setups: a fixed panel for the basics, plus a portable one for the days you park under a tree.
Whichever you pick, it needs a controller that copes with the panel's voltage and current. That's in how much solar do you need, and if you're choosing one for a portable panel, MPPT vs PWM solar controllers covers why MPPT does better in shade, cloud and the cold.
All four types are in our solar panels range.