Choosing a 40W portable solar panel is less about finding the highest number on a label and more about matching the panel to the way you travel. The FlexSolar E40, E40 Pro and S40 all share a 40W rated output, yet they differ in folded size, connection options and the kind of gear they are best suited to charge.
This guide compares the three models side by side so you can choose the right solar charger for camping, hiking, road trips and everyday outdoor use.
Quick answer: which 40W panel should you choose?
- Choose E40 if you want the widest connection range, including USB-C PD up to 40W and a 19V DC output, in a long six-panel design that can attach to a backpack.
- Choose E40 Pro if you want the same 40W USB-C capability and 19V DC output in a shorter five-panel format with a compact book-style fold.
- Choose S40 if your priority is a slim, lightweight USB charging panel for phones, tablets, cameras and power banks.
E40 vs E40 Pro vs S40: specifications at a glance
| Specification | E40 | E40 Pro | S40 |
|---|---|---|---|
| Rated power | 40W | 40W | 40W |
| Panel layout | 6 panels | 5 panels | 4 panels |
| Unfolded size | 48.8 × 11.1 in (1240 × 282 mm) |
44.96 × 9.84 in (1142 × 250 mm) |
36 × 12 in (913 × 304 mm) |
| Folded size | 11.1 × 8.0 × 1.8 in | 9.84 × 8.98 × 1.8 in | 12 × 9.8 × 0.7 in |
| Weight | 26.5 oz / 750g | 26.5 oz / 750g | 24.7 oz / 700g |
| USB-A | QC3.0, up to 18W | QC3.0, up to 18W | QC3.0, up to 18W |
| USB-C | PD, up to 40W | PD, up to 40W | PD2.0: 5V/3A, 9V/3A, 12V/2.5A |
| DC output | 19V/2.1A | 19V/2.1A | No |
| Indicator | Single LED | Power LED + 3-color output LED | 3-color output LED |
| Warranty | 12 months | 12 months | 12 months |
From left to right: E40, E40 Pro and S40 in their folded form.
FlexSolar E40: the versatile all-rounder
The E40 is the longest of the three when unfolded, using six solar sections across a 48.8-inch span. That shape gives you multiple attachment points and makes it practical to hang vertically from a backpack during breaks or lay flat in an open area at camp.
Its strongest advantage is connectivity. The USB-C PD port supports up to 40W for compatible devices, the USB-A QC3.0 port covers common phones and accessories, and the 19V DC output can connect to compatible equipment that accepts the panel's voltage, current and plug specification.
Best for: hikers and campers who want one panel for USB devices plus compatible DC equipment.
FlexSolar E40 Pro: compact without giving up connections
The E40 Pro keeps the same 40W rated panel power, USB-C PD output up to 40W and 19V DC connection in a shorter five-panel layout. Folded, it measures 9.84 × 8.98 × 1.8 inches and weighs 1.65 lb (750g), making it easier to fit beside other travel gear.
The added output indicator makes it easier to see whether the panel is delivering power under current sunlight conditions. For travelers who want a compact book-style panel without losing DC support, this is the most balanced option in the group.
Best for: camping, road trips and compact travel kits that need USB-C, USB-A and DC outputs.
FlexSolar S40: slim, lightweight USB charging
The S40 is the lightest model at 24.7 oz (700g) and folds to only 0.7 inches thick. Its four-panel layout opens to 36 × 12 inches, so it needs less horizontal space than either E-series model.
S40 is designed around USB charging rather than DC equipment. It includes USB-A QC3.0 and USB-C PD2.0 outputs for compatible phones, tablets, cameras and power banks. If you do not need a 19V DC connection, its thin profile makes it an especially simple everyday travel option.
Best for: travelers who mainly charge phones, tablets, cameras and power banks.
How to choose the right 40W portable solar panel
1. Start with the devices you actually carry
Choose by input requirements, not panel wattage alone. A phone and a small power station may both charge from solar, but they can require different ports, voltages and charging protocols. Always check the device's accepted input before connecting it.
2. Decide whether you need DC output
If your setup includes compatible DC equipment or a small power station with a matching 19V input, choose E40 or E40 Pro. If your kit is entirely USB-based, S40 offers a slimmer design without an unused DC port.
3. Compare packed shape, not only weight
The three panels are close in weight, but their folded dimensions differ. E40 Pro is the most compact book-style option, while S40 is the thinnest. E40's longer six-panel form provides a different attachment and setup profile.
4. Plan for real outdoor conditions
Rated power is measured under controlled test conditions. Actual output changes with cloud cover, panel angle, temperature, shade and the connected device. For better results, unfold the panel completely, point the full surface toward direct sunlight and keep every solar section clear of shade.
Frequently asked questions
Can a 40W solar panel charge a laptop?
E40 and E40 Pro provide USB-C PD output up to 40W. They can charge compatible USB-C devices whose input requirements fall within the supported output, although charging speed depends on sunlight and the device. Check the laptop's power requirements first.
Can these panels store energy?
No. The panels generate power in daylight; they do not contain a battery. Connect a compatible power bank or power station if you want to store energy for later.
Are the panels waterproof?
The panels are designed for outdoor use, but ports, junction boxes, cable connections and connected electronics should be kept dry. Do not leave the panel exposed during heavy rain or immerse it in water.
Why is the output sometimes below 40W?
40W is the panel's rated output under standard laboratory conditions. Real-world output varies with sunlight intensity, angle, temperature, partial shade, cable loss and the charging limits of the connected device.
Final recommendation
Choose E40 for maximum versatility, E40 Pro for a compact all-round setup, or S40 for a thin, lightweight USB charging solution. All three are built around the same goal: practical solar power that is easier to take outdoors.