It is, in fact, extremely hard, even in theory and more so in practice, for most countries to replace most energy use with energy from renewable sources, unless we go with nuclear energy. See e.g. [1].

With world wide effort, electrical connections spanning the globe, tropical countries selling solar power to colder regions, huge and cheap energy storage facilities, we could maybe achieve that, though I'm really rather rooting for fusion, which should be economically available in only a few decades.

[1] - http://www.withouthotair.com/