I don't completely buy into the notion that conservatives here are conservationists. I think there definitely are some that are, but I think larger contributing factors are that we have an abundance of renewable energy (hydro, wind, and sun), low population, and a ton of federally-owned land.
We have so much hydro power that some of our dams aren't even owned by Idaho Power. For example, Lucky Peak Dam, which provides flood control for the Boise River and Boise, has a power plant there that is actually owned by Seattle City Light that provides 4% of Seattle's power (1).
Also, Idaho doesn't have a lot of fossil fuels to harvest (2), so this likely plays into lack of desire for coal. Mining in the north and agriculture in the south are our primary economic drivers.
In terms of the politics, our legislature this year just barely formed a committee to discuss climate change, but our governor did say it exists and is a problem, so who knows? I suppose I tend to think that our population's demand for electricity is no where near greater than our supply, which is why demand for coal isn't really there.
However, if someone from the outside wanted to install a coal power plant, I think conservatives here would easily support it. That may be my cynicism coming through, but I could easily see Trump advocating for it and then the freedom trucks with their freedom flags and freedom coal rolling exhausts would rally to support this.
Yeah, I'm a tad cynical.
1. http://www.seattle.gov/light/history/brief.asp 2. https://www.eia.gov/state/analysis.php?sid=ID