With the plummeting price of solar cells, you can buy inexpensive portable solar panels online or at many big-box home-improvement centers. Many foldable solar panels can be bought at roughly $1.00-$2.00 per watt—about half what it would cost to have solar panels installed on your roof. But are they worth it? Let's find out.
How Portable Solar Panels Work
Unlike a solar panel that you might place on your roof, which is set in a fixed, rigid frame and sealed under glass, a typical portable panel is usually encased in a protective sleeve made of mesh fabric or plastic. Small, inexpensive (under $50) panels will generate 5 to 50 watts, while larger ones can generate 300 watts or more—the same as an average rooftop solar panel. Smaller panels are often a single sheet of silicon solar cells, while larger panels might have two or three panels in a foldable case.
The panels come with a simple jack or set of jacks to output power to a variety of devices. You're likely to find a DC output jack and a USB port, allowing users to directly charge phones or laptops. Most often, portable solar panels are paired with a portable lithium-ion battery so that their energy can be used under any conditions. (You can't charge the battery while it is in use, however.) The battery can have a larger range of output devices, from standard household 120-volt AC outlets to DC output jacks.
While the output of some of the larger panels can be equivalent to a regular rooftop solar panel, portable panels are not meant to replace rooftop ones. By design, they lack the structural integrity and voltage regulation of a properly installed rooftop solar system.
On the other hand, setting up a portable solar panel takes minutes, needs no permits or inspections, and there's no worry about damaging your roof.
All solar photovoltaic (PV) panels are made of crystalline silicon wafers that absorb sunlight. The light (photons) from the sun knocks electrons loose from the silicon material, creating a current along the electrical conductors in the cells (thus the term “photovoltaic”). The current flows in one direction—direct current, or DC—out from the cells, either directly into a device that accepts DC electricity (such as a battery) or indirectly through an inverter to create alternating current (AC) for most household uses.
Top Uses for Portable Solar Panels
Because these panels are portable, they are often used by campers, travelers, or anyone who needs a supply of electricity when unable to access grid electricity. But because they come in so many different sizes and costs, there are a variety of other uses as well.
Treehugger Tip
Read the manual carefully, and only use the solar panel with approved devices. Depending on the capabilities of the solar panel or solar-powered battery, you may not be able to power electronic devices, household appliances, delicate medical equipment, or electric vehicle batteries, which require voltage waveforms that are less variable than the output from a solar panel or battery.
Camping
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Camping and hiking are perhaps the most common uses of portable solar panels. You can fasten larger panels to the top of your van or RV to provide an alternative to a portable generator. Unlike a noisy, smelly generator burning fossil fuels, a battery charged by solar panels is clean, quiet, and odorless. Since even the larger panels are portable, you can place them in the sun while your tent, camper, or RV stays cool in the shade.
If you're on a week-long hiking trip into the back country and want to keep your phone charged for GPS or emergency purposes, a small solar panel that slips into your backpack can keep you in contact with civilization. Larger panels can weigh 25 pounds or more, so they are better suited for car camping than hiking the entire length of the Appalachian Trail.
Boating
Place solar panels on the deck or other flat surface of your boat and you can run an electric motor with the power stored in a battery. The panel can also act as a canopy to protect you from the sun when you are out at sea. When paired with a solar battery, solar panels allow you to sail without the the need for wind or the noise and smell of a gas-powered motor. And as long as the sun shines, you can sail nearly infinitely without needing to make refueling stops.
Special portable marine solar panels are available for solar boating, since they need to withstand corrosive salt water and fiercer weather conditions than a camper may experience.
Warning
If your panel is exposed to light, it's generating electricity, so to avoid electric shock, above all, use common sense. Do not immerse it in water, bend, pierce, or break it, expose it to heat or flame, or disassemble it. If it needs cleaning, use a slightly damp cloth without soap. Read the user manual for other safety warnings.
Apartment Living
If you live in an apartment and your landlord isn't willing to install solar panels on the roof, you can either consider a community solar farm or set up portable solar panels on a balcony to generate your own electricity. When you move out, you can take your panels with you.
Power Outages
If you work from home and your power goes out, your modem and router go out as well, so if you don't have access to a wifi hotspot, you have no access to the Internet. With a solar-charged battery backup, however, you can continue to run your modem, router, and laptop until the power comes back on. There are also portable solar panels that are designed specifically as solar laptop chargers. Depending on the size of the battery, you also may be able to run a small dorm room-sized refrigerator to keep food or medicines from spoiling.
Think Outside the House
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You can keep an outdoor structure such as a greenhouse or hot tub warm, light up a patio or backyard play area, run the pump on a fountain or bird bath, or power outdoor holiday decorations without having to run electricity from your home.
Reduce Your Carbon Footprint
If you get your electricity from a grid that doesn't run on 100% clean, renewable electricity, you can reduce your carbon footprint by using your solar panels to run some of things in your home that require electricity. You can cut down on your electricity bill and assure yourself that you are using carbon-free energy.
What To Look For When Buying Portable Solar Panels
When shopping for portable solar panels, here's what to look for. Treehugger has reviewed some of the best of them.
Efficiency
If space or weight is a concern, such as in backpacking, compare the efficiency of various solar panels. The efficiency of a solar panel is measured by how well it converts sunlight into electricity. A panel with an efficiency over 20% is a quality product. A more efficient panel needs less room to generate the same electricity as a larger, less efficient one, but it may cost more. If space or weight is not a concern, don't waste your money on a highly efficient panel if a lower-cost, less efficient panel will get the job done.
Buy What You Need, Not What You Want
Know what you'll need and don't buy more than that. You can calculate how much energy you need with a simple energy calculator which tells you how many watts different appliances use. Check the voltage requirements of any gadget. Most laptops, for example, require 19 volts of constant power.
Know Your Watts and Watt-Hours
A watt is a unit of power. It measures how much energy a device will consume or produce at a single moment in time. You'll need a solar panel (or battery) that can produce 100 watts to light up two 50-watt light bulbs.
A watt-hour is a measure of how much energy is used over the course of an hour. If you want to keep your two 50-watt light bulbs lit for 10 hours, you'll need a solar panel (or more likely a battery) that can produce 1,000 watt-hours, or 1 kilowatt hour (kWh). There's not necessarily a one-to-one correspondence between the watts and the number of watt-hours that a device can output. For example, the 2000-watt Goal Zero Yeti solar-powered generator can deliver 1500 watt-hours.
Treehugger Tip
Even with a solar-charged battery, a portable solar panel cannot produce enough electricity to meet the demands of an American household, which uses on average 30 kWh (or 30,000 watt-hours) of electricity per day, nor can most truly portable battery generators generate enough power to run a full-size refrigerator or heat pump. For that, you'll need a home battery storage system.
Weight
Weight is not only a factor in terms of a panel's portability but in also terms of the amount of electricity it might generate, if only for the practical reason that you are more likely to move around a lighter solar panel than a heavier one if you want it to follow the path of the sun throughout the day, allowing it to generate more electricity.
Other Considerations
A portable solar panel is certainly a cleaner source of electricity compared to most alternatives, but to make it worth the investment, consider its financial worth as well as its convenience.
How often will you use it? Will it save you money over the alternative? Given the wide variety in size, capacity, and cost of all the different portable solar panels on the market today, you'll probably be able to find a good use case for one.
