What to look for in a portable solar charger
If you are looking for a good solar charger, there are many things to consider. First and foremost, you’ll want to decide what you’re going to use it for and how many devices you’re going to use it for. Second, consider how long you will be in the country and how much storage and battery power you want to carry.
We looked at a variety of solar chargers and, in some cases, energy storage units (also known as batteries). We also came up with different conclusions than other review sites based on our knowledge and our expectations of how you will be able to use the solar charger in the area.
For example, unlike many other reviews and ‘best of’ lists we’ve checked, we strongly recommend using solar chargers with backup batteries. Many high-end electronics such as smartphones and tablets require constant, regulated, or conditioned power to charge. It helps limit the amount of damage a surge or dip in solar power can do to sensitive electronics inside the device.
Efficiency and power output
Efficiency and power output are two different, but related things. Efficiency refers to the efficiency of the solar cells in the panel and the panel itself. The solar cells in a panel have a higher efficiency than the panel as a whole since some of the energy they absorb is lost in the transmission of power through the wires and electronics of the solar panel. The most efficient solar cells are 24 percent efficient. A solar panel or charger, however, is likely to be efficient at 18 to 21 percent.
Power output is measured in terms of solar power consumption or how many watts of power a solar panel can produce. The more efficient a solar panel is, the more watts and amps it can put out in a smaller area. For charging equipment you’ll want a solar panel capable of producing at least 5 watts, but more portable solar panels produce up to 28 watts of charging power in the right conditions. Higher wattages equal more charging power—however, since most of these solar panels still use USB-A style plugs, they can only produce 2.4 amps of current from those plugs.
Portability and size
The smallest outdoor solar panels we’ve tested are 5 watts. These are about the size of an average tablet, like the BioLite SolarPanel 5+, and weigh less than a can of beer. They can generate enough power to partially charge a smartphone or other device. At 8 inches by 9.75 inches, they’re easy to fit in a daypack.
The largest portable solar panel we tested was 6 pounds Zero Nomad 50 goalit folds to just over 17 inches long and 11 inches wide and is over an inch thick at its thickest parts, making it difficult to fit into most backpacks. When set up it folds to 53 inches wide. It was also the most powerful solar panel we tested and can charge a battery that can charge laptops.
Durability and weather resistance
Although these panels will last for years and even decades with proper care, they are not designed to be left out in the elements like permanent installations. They are covered in scratch-resistant fabrics and plastics and are collapsible.
The solar cells are covered in resistant plastic and the units usually have a water resistance rating of IPX4, which means they can handle splashes of water but not more. That shouldn’t be surprising since most portable solar panels have standard USB-A ports without a waterproof cover.
Battery capacity
Most of the solar panels tested do not have batteries. The BioLite SolarPanel 5+ and BioLite SolarPanel 10+ have 3,200 mAh batteries. That’s enough to almost fully charge an iPhone 16 in one go. You can also pre-charge these batteries before you go and use them to charge the device while it is in your pocket or at night and recharge the battery in the sun.
The exact speed of solar charging
If the solar panel is properly placed in full sun it should be able to produce its maximum amount of water. In these cases, the panel should be able to provide enough power to charge 2 USB devices simultaneously at 2.4 amps, similar to most 12-Volt USB adapters used in cars.
Solar charging speed for multiple devices
In ideal conditions, a full solar charger of 20 watts or more with two (or more) USB ports should be able to charge most devices at up to 2.4 amps such as most 12-Volt USB adapters used in cars. A more powerful panel should be able to charge more, but the device should be able to handle higher charging amperages such as those using the USB-C connection.
Additional features and resources
Most portable solar panels for camping are very small in terms of features. Most include mainly a panel and USB ports. Additional features include a pocket for cables, grommets or loops to attach the panels to a pack or tent, and in some, stands to help keep the panel upright and at the right angle. A few, like the BioLite panels, have integrated batteries and have a small sundial that helps users to properly orient the panel so that the ideal sunlight reaches the solar cells.
When it comes to accessories, there are two main accessories that you can use with solar panels, wires again batteries.
We highly recommend using these with a backup battery rather than plugging a smart device into them. Some smart devices limit the speed at which devices can charge when working with a variable energy source, such as a solar panel. Backup batteries, however, can better harvest the alternating currents flowing from the solar panel.
Value and value for your money
The price of basic solar panels isn’t too high, around $70 for our Best Picks, BigBlue 28W USB Solar Charger. If you have a spare battery already on hand and know you’ll last several days and need extra power for camping, it’s a decent investment.
If you’re hoping it will power your devices while you’re strapped out of your pack and hiking, you’re not going to be happy. Despite the promotional photos, even in sunny Colorado when we tested all the devices, these panels weren’t good at delivering consistent enough power to charge devices while carrying them in a pocket.
Integrated Battery or power bank
Unlike many other reviews and ‘best of’ lists we’ve checked, we strongly recommend using solar chargers with backup batteries. Many high-end electronics such as smartphones and tablets require constant, regulated, or conditioned power to charge. It helps limit the amount of damage a surge or dip in solar power can do to sensitive electronics inside the device.
Additionally, carrying a spare pre-charged battery or power bank and a way to easily charge all your devices when you’re in town or in your car can reduce the amount of charging you’ll need to do on the road. Precharging or recharging a spare battery or power bank through the wall or your car will almost always be faster than charging through a solar panel.
The other two models we tested cost more. The BioLite, which is only a 10-watt solar panel, costs $150. However, it’s also the only solar charger we’ve tested with an integrated battery (sometimes called a portable solar power bank). It also has a kickstand, and a unique but simple mechanism called the Optimal Sun System, which helps direct the charger to receive the maximum amount of sunlight available. It is also unique because it is completely enclosed in plastic.
I Goal Zero Nomad 50 Solar Panel it had the highest wattage of any unit we tested at 50 watts and was the most expensive unit we tested at $250. It was also bigger and heavier, but it was the only one that could provide a charge at a higher wattage and voltage.
With such small panels, when the sky is gray, don’t expect much power output. At 50 watts, the Goal Zero Nomad 50 should still produce enough power to charge a smartphone but the smaller panels will reduce it to produce much less power, suitable only for charging a spare battery.