I did a back-of the-napkin calculation for geothermal power, which goes as follows:
1MW * 24H * 365 D = 8760 MWH per year. I expect this power to pay 10c/KWH in the future, so the Revenue per MW is ~$876k/yr. After a five year payoff on the physical plant, I would expect to see ~$0.5M/yr earnings per MW.
Given a simple P/E of ten, which is very low right now, each MW of resource should translate eventually to $5M of market cap.
If we were looking at an even longer term, eventually I would expect a 3% dividend to be paid (30% of net revenue), based on projected earnings and market cap. Of course this would be after all projects were build out, which I currently expect to take ten to fifteen years.
With Raft River #1 at 15WM, and 62.01M share outstanding, the market cap should be about $75M or $1.20 per share based on this project alone.
Since there is additional geothermal resource available there (110 megawatts according to the estimate on their website) and more at Neil hot springs (26 megawatts again on their website), and another 40 MW from San Emidio, the total MW is much higher.
Given these numbers, if they produce 176MW, the market cap should be around 800M, or $14.00 per current share.
All of this is off the top of my head, and so should be looked at sceptically. Also, it is probably only worth what you paid for it.