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Solar power technology is becoming more accessible thanks to developments like portable solar panels you can use to power your devices. That's why solar-powered phone cases sound compelling. Not only would they provide a clean energy source for the gadget you use most, they'd also mean you pretty much always have a way to charge your phone — no more carrying around cables or portable chargers.

There are various projects in the works, including one from iPowerUp that claims to be the "world's first intelligent solar case." However, a study published in The International Journal of Life Cycle Assessment indicates that solar power isn't going to make traditional phone chargers obsolete in the near future. Researchers from the University of Klagenfurt in Austria compared the two charging methods and found "the power bank performs significantly better than the solar charger." That's based on cumulative energy demand (CED), which calculates how much energy a product consumes throughout its life, from the time resources are extracted until the user throws it away.

In terms of efficiency, the power bank is also the clear winner with a charging efficiency of 64.77%. That may sound low, but it's normal for energy to be lost during the conversion and transmission process, and it's far better than solar chargers. The researchers found panel efficiency was around 10%, with the efficiency of a single cell registering at about 12%. On top of that, solar panels are (of course) impacted by weather conditions, so solar chargers are significantly less useful when it's cloudy or dark.

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Of course, one of the major draws of a solar phone case is clean energy, which is a noble goal. However, by the Austrian researchers' calculations, it would take nearly 10years for a solar charger to reach energy payback time (EPBT), the point at which the device's power production exceeds the amount of energy required to produce it. Both types of chargers are resource-intensive to produce, but solar chargers have a similar, if not higher, environmental impact than power banks, which seems counterintuitive.

This doesn't mean that iPowerUp's case won't work when it releases. However, one of the major issues, and the reason why solar panels took over calculators and not much else, is that panel size correlates to how much energy it can produce. Creating one small enough to fit on a smartphone that's also powerful enough to keep the device running long-term would be incredibly impressive.

Solar technology is advancing as researchers discover new ways to make panels more efficient and cheaper to produce. A recently published study shows solar power isn't weak, but rather being ruined by fossil fuels, indicating that solar performance could actually improve by transitioning to more green energy sources — and away from coal and oil — overall. Still, even if the kind of micro-solar panels iPowerUp says it's developed are possible to produce now or in the near future, the numbers make it clear that solar power isn't good enough yet to completely replace phone chargers.