Don’t buy a portable solar panel unless you know you’ll use it for thousands of hours. Mini solar panels are a waste of money and they’re bad for the environment.
If being “eco-friendly” is the main motivation for selection of a power source, then the most important measures are EPBT (Energy Pay Back Time) and EROI (Energy Return on Energy Invested). These measures are based on the concept of embodied energy and they help us ensure that we’re not spending more energy than get back.
A solar photovoltaic panel needs to operate for at least 3000 hours under ideal conditions just to pay back the energy that was used to manufacture it.
A miniature solar panel, such as the one shown above, can generate about 7 Watts under ideal conditions. Manufacturing the PV panel alone (not including any of the accessories, cloth, or packaging) would have consumed about 21 kWh of energy as input to the industrial process.
As a rough average, the embodied energy of a PV panel is close to 3000 Wh/WP. This means that a solar photovoltaic panel needs to operate for at least 3000 hours under ideal conditions just to pay back the energy that was used to manufacture it. Let’s be honest: almost nobody who buys a portable solar panel like this one will put it to use for 3000 hours under ideal conditions, and that means it will never produce as much energy as was used to manufacture it.
Small panels aren’t inherently bad; the real problem is that they’re going to be used with an extremely low capacity factor. Solar panels are only a good choice when they spend most of their lifetime outdoors in the sun and producing energy, just as they were designed to do. But a portable panel that spends most of its life unused in storage can never be a good choice.
Photovoltaic panels only make environmental sense as part of a permanent installation where they generate electricity for every day of their product lifetime.
Oh, and let’s quickly talk about cost. If you spend $50 on a 7-watt panel and you pay $0.20/kWh for electricity, you would have to operate the panel for over 35,000 hours under ideal conditions to produce enough savings to pay off the device. Obviously that’s just not happening.
What should an eco-conscious person do instead?
- If you’re on a quick trip, just turn off your phone. Your phone can easily hold a charge for days if you use it sparingly and turn it off when you’re outside cell service.
- Bring a spare battery. Charge it up at home while you’re still on the grid. For bonus points this also works for charging at night or in bad weather, and charges much faster than a solar panel would.
- If you’ll be spending a long time off the grid with no place to charge up, a solar panel might make sense for you. Just don’t pretend that going off-grid like this is environmentally friendly.