Nepal is the second richest country in term of water resource in the world. However Nepal has load shedding(power cut) since many years. The recent good news is Nepal is free from load shedding now days. Trekkers can charge their device easily all the time. You can bring 2 pin round or 3 pin round/universal chargers would be great. If you are also traveling country side then it would be better to have power bank too.