The Best Portable Solar Panel Review
What is the best solar charger for your phone, tablet, and other small electronics when off the grid? To find out, we took ten contenders and put them in head-to-head tests while on trips all around the country. From mountaineering on Denali to sailing off the California coast, we compared them using the following categories: output power, ease of use, weight, versatility, and portability. In the end, we found big differences in the panels we tested. Some worked well for all of our needs and some barely charged anything. Read on to find out which is the best solar charger for your application.
Read the full review below >
Test Results and Ratings
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Analysis and Award Winners
Analysis and Test Results
Solar panel technology has come a long way in a short amount of time. Not long ago, it was unrealistic to get a rigid monocrystalline panel into a portable, foldable design. Thin-film photovoltaic technologies filled a niche as a more portable option, but these are not the most durable. Today, we find a healthy mix of both styles of panels on the market, and you can choose between super efficient charging (monocrystalline) or ultra lightweight (thin-film solar cells), and a dizzying assortment of features, accessories, and qualities on the spectrum between the two. Most panels in this review are now monocrystalline, which is becoming the industry standard more and more due to its high quality, which is worth the extra cost when it helps you save weight and charge faster at camp.
In general, if you want a very lightweight and more affordable solar panel, you may consider a thin-film panel. For a more affordable option, polycrystalline is still pretty decent quality, like the panel found in the Brunton Power Essentials Kit. If you want a more timeless piece, consider a rigid monocrystalline folding panel, such as the the panel in the Goal Zero Venture 30 kit, or the Instapark Mercury 10M18U, to name a few from our review. These are bulkier and heavier, but significantly more durable. Thin-film panels tend to degrade or delaminate over time. And polycrystalline panels are less pure, and therefore less efficient.
As technology improves, companies have been making monocrystalline panels more and more portable, which is great, as these panels are much more efficient than thin-film and polycrystalline panels. The Instapark Mercury 10M18U is a good example of a portable, efficient, and relatively light monocrystalline panel that we really liked. To learn more about panel types, reference ourBuying Advice article.
This year we conducted a midseason update to catch up with Anker and their impressive 15W panel. They recently released the Anker 15W PowerPort Solar Lite. It is half the weight and half the size of the previous 14W panel, and adds even more wattage. It is made of a thin-film PET polymer this time, which accounts for the lighter weight, but does not explain the impressive jump in efficiency. This panel far outperformed all of the others in the category. It is fast, light, and friendly. That is to say, it makes friends. At basecamp on the Kahiltna glacier, the kickoff for Denali expeditions, we were able to charge all of our batteries and all of our friends' batteries--and we watched all the other solar panels sit idly in backpacks and tents while everyone took turns plugging into the new Anker 15W.
Before we get started, a short anecdote about this review:
In our testing two years ago, there was one that we just couldn't get to charge in all of its advertised capacities. It had a huge assortment of laptop plug adapters, but we could never get them to work, and there was no adapter for any Apple product (red flag!). Finally, we gave up and emailed the company. We got a very polite but useless email back, and quickly identified that it was a very, very good copycat. The packaging and everything looked identical, but it was not the reputable brand it looked to be.
This is our way of saying: be discerning in your search! Sometimes it is worthwhile to spend a few extra bucks for a reputable brand. This review will help identify several brands that are good or not as good, and how to sift through the hype.
Wait, Let's Talk a Little About External Batteries
Before we get into this review, we want to highlight that many people may be better served by an external battery. External batteries often charge a smartphone 3-6 times, can be used when it's not sunny, are compact, and usually cost a fraction of the price of solar panels or solar panels with built in batteries. If you only need 3-6 charges of your device, we recommend checking out external batteries.
This year, several of our products were kits that included proprietary batteries. We really like this setup, as it provides the most versatility. It also means we can use smaller (and lighter) solar panels, if we so choose, because we can store some extra charges in a battery. Or, we can go lighter by leaving the battery behind if we expect to have a lot of sunlight so we can charge devices directly.
Criteria for Evaluation
We ordered a very diverse array of solar chargers rom many different companies for this review, and there are a few sub-genres. Some are kits that come with folding solar panels and a separate external batteries, such as the Goal Zero Venture 30 Solar Recharging Kit, Brunton Power Essentials Kit, and the Instapark Mercury 10M18U with battery. Some are just plain folding panels, like the Anker 15W and the RAVPower 15W. While others are pocket-sized with integrated batteries: the SunFerno Flintstone, Poweradd Apollo 3, Creative Edge Solar-5+, and the Levin Dual USB Port 6000mAh Panel.
In our past reviews, there was a high correlation between the watt rating and the highest output power of the panel. A 10-watt panel, for example, was generally about two times more powerful than a 5-watt panel. Some years later, the technology has changed significantly enough that we started to notice some quality discrepancies. The simple watt rating is clearly no longer the best metric from which to judge a panel's charging proficiency.
This is a little confusing so here is an example: The Powertraveller SolarMonkey Adventurer is only rated to 3 watts, and yet is able to charge iPads and reliably charge iPhones. The Goal Zero Nomad 7 has a watt rating that is 2+ times higher (7 watts) and yet could not charge an iPad unless an external battery was used, and it ran into issues when charging an iPad mini or iPhones. This is due to amperage (current) being too low. Tablets and newer smartphones often charge best with 2A of current now.
The Anker 15W was our winner for output power. The RavPower 15W advertises more wattage AND more amperage, but in the field tests, the Anker 15W actually charged faster and registered higher amperages. This is in part due to Anker's thoughtful and progressive design: they built in the extra wattage to account for low light or energy loss in the transfer from sun to phone, keeping the amperage at 2.1 rather than maxing out the potential current at 3 A as RavPower did in their design.
Ease of Use
This category is a catch-all for the overall quality of a panel--this is where we assess if a panel is too glitchy or counterintuitive, or if it is so slick you don't even notice it in your life. In the field, this can mean many things, from tie-down or hanging options to stash pockets for your device. More and more, panels are starting to exclusively charge USB devices--the Powertraveller Solarmonkey Adventurer is the only exception in this review. This means that the panel can be easily shared with multiple different devices and smart phones. All you need is your device's charging cable. This is a welcome change from panels of the past, when they came with so many adapters it looked like a socket wrench set (and required OCD skills to keep everything organized.).
We found panels that include a sewn-on storage pouch to be immensely convenient. They provide a convenient place to store your charging cables, and keeps your device clean and out of the wind or direct sun while charging. Our favorite pockets were on the panel included in the Goal Zero Venture 30 Kit and the Instapark Mercury 10M18U with battery. The Goal Zero's mesh pocket is big enough to hold the Venture 30 battery pack plus your smartphone. The Mercury 10's pouch houses two USB ports, and is generous enough to hold your phone, an extra battery, and the USB charging cable. The Anker 15W had the weakest pouch closure we used, which was annoying at times and would not handle a modern size smartphone. The SolarMonkey Adventurer also comes in a zipper pouch that can hold charging cords, but this mini-briefcase design was too bulky for most of our lightweight travel needs.
The Goal Zero, Anker, and Instapark Mercury 10 panels come with string loops attached at the corners which allow you to hang the panel from bushes or hooks or tents, etc. These made setup and orientation of the panels much easier, and when we folded them up for storage, they also folded flatter.
Weight gets high weighting in our scores, pun intended. After all, the whole point of a portable solar panel is to be, well, portable. A panel that weighs less than a pound and is very compact is generally all we take for most outdoor situations: hiking, backpacking, biking, and climbing. If the panel weighs more than a pound and a half, it really needs to do some heavy duty charging of multiple devices and/or a laptop and is probably not ideal for carrying on a self-supported trip. If you are boating, weight doesn't really matter. Take that into account when looking at the scores.
Also, consider that weight will increase if you need to bring multiple charging cables and/or a case. The weights in our spec sheet will indicate total weight of the setup we reviewed.
Many of the pocket-sized integrated solar panel/battery devices win by miles for light weight. If you're looking for something very minimal, the Creative Edge Solar-5+ or the SunFerno Flintstone might be just right. For most applications, however, they were too slow to charge via sunlight to really depend on them as a solar chargers.
The heaviest in our review is the RavPower 15W. With the new design of the Anker 15W, it is no longer in the heaven category with the RavPower. The Anker now officially obliterates any of the RavPower's competitive edge.
The lightest was the SunFerno Flintstone which, despite its limits, might still fit your needs.
With the entire internet at your fingertips, in a device small enough to fit in your pocket, who wants to carry around a big, bulky solar charger? Fortunately, the days of cumbersome solar are over. The market is flooded with lightweight, simple, and very compact panels--and the deluge of design and innovation doesn't appear to be slowing any time soon.
Mostly, we were looking for devices that are light, and not cumbersome. It's a brave new world--solar technology has emerged from the realm of electrogeek to sexy cyber chic.
Last year, the Apollo 2 was the new kid on the block, a sleek smartphone sized battery with a solar panel. This year the market is flooded with similar chargers, but none as good as that Apollo 2, including the very disappointing Poweradd Apollo 3. But for a little charge and a small solar recharging capacity, the Creative Edge Solar-5+ and the SunFerno Flintstone proved relatively reliable and very, very portable.
Versatility is important to some and trivial to others. If all you need to do is charge a cell phone, you can gloss over this metric. For a simple phone-charger, all you need is a lightweight device with a USB port.
However, if you want to charge multiple devices and bigger devices like a laptop, then versatility is much more important. None of the solar systems in this review can charge a laptop, but there is a strong distinction between those that can reliably charge a tablet and those more limited to smartphone charging.
The Goal Zero Venture 30 battery is by far the most powerful way to charge up your high energy devices. Both USB charging ports will charge up to 2.4A at the same time. The Powertraveller Solarmonkey Adventurer is an interesting solution to the need for versatility. The recent upgrade may be just what you're looking for. And then there's the Brunton Power Essentials Kit which is not powerful, not light, and limited in many ways, but reliable at a relatively low performance level.
Many people choose to combine a solar charger that doesn't have an internal battery with an external battery. This allows the panel to charge the battery during the day while the device is being used. Then the device can be charged at night from the external battery.
External batteries are an increasingly important addition, too, because as our tablets and smartphones demand higher power (like 2A charging ports), this becomes more difficult to produce from the sun (which is variable at best), and requires higher wattages, and thus more panels, meaning more weight and bulk. The best option, in our opinion, is to have a less powerful (and lighter weight!) solar panel that charges a high quality external battery, which can, in turn, produce the necessary 2A of current for our modern devices.
Home Solar Panels
The world headquarters of our sister site, SuperTopo.com, is now solar powered. Check out this detailed guide on how to choose home solar panels. The article contains photos, video, and many external links to help you evaluate if going solar is right for you.
Ask an Expert: Patrick Sherwin
Patrick Sherwin has been an innovator in the solar industry for the last 15 years. He's a LEED and NABCEP certified installer and owns his own solar panel installation company, has developed solar integrated electric vehicle charging stations, and has spent over two years living off the grid in the Bahamas and Ohio. His latest invention, the Go Sun Stove, is a high-efficiency portable solar cooker that uses nothing but the sun's rays to bake, boil, or stew your food. Patrick shared his expertise on how to choose the best solar setup for your needs.
What's the longest amount of time you've used a portable solar charger for?
The longest I've lived off the grid expedition style was a two month trip down the Amazon River in Peru. We used a Brunton SolarRoll Solar Panel to power our trip, and that kept our satellite phone, laptops, and camera batteries charged for weeks at a time.
How do you figure out what size panel or system you need?
I rarely say this in life, but in the case of solar charging, I do think bigger is better. You might only want a system to charge your phone, but then out in the field your buddy needs his phone charged too, so now you need double the capacity. Then you might buy a rechargeable headlamp and start growing in your consumption. So you want to try and size it right from the beginning.
First, calculate how many appliances you want to charge, say a phone, a camera, and two flashlights, and then calculate the wattage needed to charge them. Once you know how much it takes to charge those four appliances, you need to keep in mind that the system's ratings are what could happen in the ideal scenario, but how often are you operating in those perfect conditions? It might be 5 pm, or it's partially cloudy and the panels are super dusty and muddy, so maybe you actually need double the wattage. That's why it's always important to go bigger.
You then need to consider how many days you will be out relying on the charger, and you can also add in the metric used in off-grid system design, which is 'days of autonomy,' or how many days you might go without any input from the sun. Days of autonomy depend heavily on where you live. In Ohio, when I do off-grid design I calculate three days, but in the desert southwest you can generally just use one. The longer you plan to be out and the more days of autonomy that you add, the more expensive and heavy your battery system is going to be.
What features do you look for in a portable charger?
I prefer using the mono and multi crystalline technology over the amorphous thin-film designs. The crystalline panels are a more proven design, more efficient, and generally take up less space. Another reason I prefer the more rigid and/or foldable panels is because the surface treatment of the cells can be rigid as well. Flexible surface treatments, like on the roll-up models, can delaminate over time, and are more difficult to clean because they are rubberized. Foldable panels can be just as lightweight as a rolled up one, because it takes less surface area to generate the same amount of power. Finally, crystalline panels have a lower per/watt cost than thin-film ones, but while they can handle some impact, if you crack the cell they won't work anymore.
The user interface is also key, and that technology has improved a lot over time. Ten years ago they had a bunch of alligator clips and loose wires, and it was a very backyard do-it-yourself ethic. Wires would often spark when plugged in, which wasn't dangerous but definitely disconcerting to a novice user. This is where companies like Goal Zero have done a great job of creating user centered modules that are much more plug and play.
What determines the efficiency of a panel?
Efficiency is a rating of how much of the sun's input a panel is capable of converting to energy. It just so happens that peak sunlight produces about 1000 watts per square meter. That is a universal constant at high noon in July, and that is the standard test conditions that manufacturers run from, but that is not the reality all the time. The efficiency of this kind of micro solar really tends to vary a lot, and is determined by the cell technology, or the silicone's ability to convert sunlight into electricity, and then the efficiency of the entire assembly.
For mono and multi crystalline panels, the average efficiency is about 15%, with 20% being the high end. Then there is an entirely different style of panel, which is the amorphous silicon or thin-film design. The amorphous silicone allows the photoactive layer to be 'painted' on the base layer, which can be a flexible material. This helps to create a more portable unit, but it is not as efficient as the rigid style, typically only getting around 8%.
So you would need about twice the surface area of thin-film solar to produce the same power as a rigid panel. This is generally not that big of an issue when talking about a household array or a solar field, because there is a lot of space, but in the portable world you want something that's lightweight and easy to transport. Figuring out how to create foldable panels of crystalline cells was a huge advancement over the thin-film design, because now you can have an efficiency of 15% in the field.
Would you recommend buying a unit with an external battery? Or just going with an external battery instead of a solar charger?
It is really smart to have the battery integrated into the design. It's not critical, but when you are buying a system it is important to consider the loads – what are you powering, for how long and when (what time of day). This is the basis of off-grid design. When you are living off the grid the reality is that it's not about living off solar, it's about living off battery. I would recommend getting an integrated system where the battery and panels are matched to each other to cooperate consistently. Then what you really work towards is powering the battery, which becomes the hub that you can pull energy from when needed.
In many cases you can size an external battery to suit your needs instead. I carry around a lithium ion battery that can charge my phone three times, and it only weighs a pound. So I can power that up during the day with a 10 watt solar panel, and charge my phone off of that.
In our testing, we found that some of the ratings did not correlate with the actual power output. Why is that?
The misleading thing with solar panels is that they will create voltage very easily and under minimal light conditions. When manufacturers are rating panels they might have more emphasis on flash testing, which will produce misleading results. Testing devices can measure how much voltage is created by the cells, and then the watt rating is determined by multiplying it by the amperage, or current, but if the amperage is over estimated then the overall rating will be skewed.
The panel might create a high enough voltage to charge your phone, but there might not actually be enough current to make that happen due to the small size of the unit and also the efficiency of the panel. So it's easy for manufacturers to convince folks based on their testing procedures that a panel produces 8 watts when in reality it never makes that much.
How important is it to properly orient your panel and what's the best way to do so?
It is really important to get the right orientation. You have to make sure that you are perpendicular to the sun within plus or minus 20 degrees, and that's called the tilt angle. The other angle is east to west, called azimuth, which is equally important. Both of these angles are hard to achieve when you are travelling and moving. Getting the right angle is a critical issue when winter camping, as you have to really get a steep tilt angle in order to capture sunlight. It is less of an issue in summertime travel or tropical locations, when orienting it horizontally is just fine, as you will likely fall into that 20 degree window or so.
You rarely want to put the panel in a vertical position, say hanging off a table or a backpack. You almost always want to put it horizontally, except in winter months when the sun angle is super low.
One design feature is that a panel will have hooks that you can use to attach it to your pack when hiking. Are you realistically going to get much charge from that?
Probably not much. Maybe if you have a smart battery that can handle constant changes in voltages. I think you are better off putting it on the brain of the backpack, on the very top where it's mostly flat. In all honesty, I'm not really feeling this whole wearable solar trend. The production is just so minimal.
What sort of maintenance do you need to do to increase the charging performance and longevity of the panel?
Keeping the panel clean is very important, particularly on the surface that's collecting sunlight, and to do that you should use a non-abrasive cloth and cleaning solution. A little dust might only give a 5% reduction in performance, but if it's covered with mud then it's not going to work very well. Dust and dirt are your main maintenance concerns.
There is the potential to have some corrosion on your connectors, and so you want to keep an eye on that. An easy way to deal with corrosion is to use a little sandpaper to clear it out.
Any good solar energy stories you want to share with us?
During my expedition in the Amazon, we ended up at a remote ranger station, called a 'point of vigilance' against illegal logging. The station was being threatened by illegal loggers who were taking old growth trees from very remote parts of a protected area of the jungle, and the rangers were having trouble communicating via radio to their main office. They were worried that they were going to get ambushed and would have to abandon their post for their own safety. When we arrived, we had some tools with us and we took a look at their solar system, and sure enough so much corrosion had built up on all the terminals and all the terminations that it was probably running at only a quarter power. We rewired their system, cleaned it up and got it running, and they maintained their point of vigilance.
History of Solar Chargers
By Andy Wellman
Humans have been trying to harness the power of the sun for millennia. 2700 years ago we were using magnifying glasses to start fires, and the use of passive solar technology has been recorded throughout the ages since. The ability to turn the sun's energy into electricity was first discovered in 1839 by a French scientist name Edmond Becquerel. He found that when he placed two metal electrodes in a conducting solution and then exposed it to light, electricity generation increased, and he dubbed this 'the photovoltaic effect.' It still took over another century for the modern silicon based photovoltaic (PV) cell to come into being, thanks to work done at Bell Labs in the 1950s, and the technology was quickly adopted by the space industry for use on satellites. At that time, it cost around $200 to produce 1watt of power.
The 1970's saw greater use of PV cell technology thanks to a decrease in costs, as well as oil insecurity. The first homes that ran on solar energy were built, and 'thin film' solar cells were developed. In the 80's and 90's the first large scale solar power plants were constructed, and solar panels started to appear all over, from experimental cars and planes to the basic calculator that every kid took to school. As the efficiency of PV cells increased and the per watt cost continued to decrease, household solar arrays became more frequent and some do-it-yourselfers were fashioning their own solar chargers using single panels and car batteries. In fact, keeping a car battery topped off was one of the original consumer demands for this technology, and solar battery chargers are still commonly sold today.
The other demand for portable solar came from the outdoor industry. As our use of electronics in the field increased (such as satellite phones and laptops to update expedition blogs), so too did our need to power them. The first portable commercial solar chargers came on the market a little over a decade ago. Brunton was an early adopter of the technology, though their first chargers were more rudimentary and required a bit of electrical know-how. The first computer laptop solar charger debuted at the Consumer Electronics show in 2008, with a 15 watt panel that could charge a standard laptop in a few hours.
Goal Zero revolutionized the solar charger market when it launched in 2009, with an emphasis on design, ease of use, and humanitarian focus. While solar chargers might be a niche camping or survivalist trend in North America, in the developing world or in disaster relief situations it has lifesaving implications. Goal Zero has donated hundreds of thousands dollars' worth of merchandise to people afflicted by large scale disasters, such as the earthquake in Haiti in 2010, the Japan earthquake and tsunami in 2011, and Hurricane Sandy in 2012.
Today, the use of solar energy continues to grow at an exponential rate. Over the last decade, global production has increased 53 times, from 3.7 gigawatts in 2004 to a staggering 138 gigawatts today. Costs have decreased to less than $1/watt for large scale productions and an average of around $5 per watt for household arrays (however portable costs are still in the $10-20/watt range). Though portable solar is still a small slice of the overall energy production, is does fulfill a critical need in many situations.
We hope that our thorough tests and reviews of these products will be useful to you as you shop around for your new solar charger. If you need further assistance in finding the model that best suits your needs, check out our Buying Advice article.
— Lyra Pierotti
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