Product Reviews

Solar panels rely on efficiency and surface area, and while the former is improving all the time, you still need a healthy dose of the latter to power larger devices. The E-Sun takes 104 x 54cm to provide 25W, more than is available on even the largest window sill, although the panel is made of rubber and can fold up into a pouch smaller than an A4 document, making it very portable.

Its power output falls somewhere between small, handheld solar chargers and permanent installations, but offers greater convenience. You could easily take this camping, but it serves equally well in a garden or balcony. But the 25W measurement, as with so many marketing claims in the electronics industry, is a theoretical maximum and not what it will provide on an average day. We managed to squeeze enough power out of a day's sunshine to run a laptop for a couple of hours. And while this energy may be free, at £319 it will take some time to pay for itself.