My view is that solar electric power is the most important item to develop. Although there is a good argument for diversity in the base energy source, solar really is the source of it all. Nuclear and geothermal are not immediate products of solar energy, but were in the distant past. I thought this article useful for showing us the possible and the cost:

New Jersey Utility Approved to Install 80MW of Solar for $515M

This scheme is using many photovoltaic panels atop power supply poles as well as in some places on he ground. As can be seen the installation cost is $6.5 per Watt. That Watt is supplied every second the sun is shining so that upfront cost of $6.5 will provide maybe 5,000 kWh over a year; this is not any new technology it tacks onto existing infrastructure.