Well, it's still a 5 volt source. I haven't timed it, but it didn't -feel- like it took longer that using the wall charger.

But -- what does take time is charging the solio device. The solio has it's own battery that charges from the sun, this battery is what charges the N800. That's why it's not slow to charge the N800. But it takes 24 hours (*) of light to charge the solio, from dead to full. (And it can be charged from the USB port of a computer, that's much faster.)

(* I don't have the manual in front of me, I'm typing from memory.)