OK

Your options were Coal, Nuclear, Natural Gas and Renewable Energy. You also asked to mention environmental effect. Fair enough, if you really are asking to understand not just argue.

Coal and Natural Gas are fossil fuels. A typical coal and natural gas plant costs hundreds of millions dollar (here in US, a clean coal plant could cost 1.8 billion). Even if we get investment to build them, where are you gonna get Coals and gas from? We don't have any credible coal or gas mine that has been explored. US does. So are you suggesting we buy them? Add this operational cost with the plant building cost. A typical coal plant would cost 1300 per KW hour. Nepal, w/o any such natural resources would be costly place to venture in these plants.

Nuclear. A good clean energy. First of all a nuclear plant is more expensive to build, costs billions of dollars. Second, we don't have source of enriched fuels. The cost per KW hour would be as high as coal if not higher. What about the spent fuel and proliferation fears?

Renewable energy is a good bet. Solar and wind power are the only ones we can harness at this time practically, maybe even geothermal. But their output is limited and unreliable and cannot be sole means of providing a building nation's power. They are, however, an essential factor to supplement hydro.

So why hydro? It is not out of fashion, these things are not a matter of envogue or not. Nepal is the second most powerful nation in the world, in terms of hydroelectricity capabilities. Hydro is one of the renewable source of energy and the running type (unlike dams) are the best way to harness them without any ill effect.

So my friend, say you already own a car and you are running late for office. Would you rather drive your car to work or go buy a jet, a concord or a rocket instead to get to work?