Find meaningful power plant varieties, don't put them in the game only for "realism". Given the obvious baseline of "whatever power plant type is appropriate for a planet and its resources", making the player decide what power plant to build, or even explicitly giving details of what the actual power plant types are, should bring some value to the game:

• There could be important "side effects" beyond energy. For example, a fission power plant can produce weapon-grade plutonium in addition to energy, which matters a lot if nukes are an important weapon, geothermal plants can make cold planets habitable, and exotic ultra-tech power plants could be high performance but easy to blow up.
• There can be ties to the story and world settings. For example there could be a choice between mundane power plants and advanced alien technology-based power plants that perform much better, can be obtained as a favor from a certain faction, and can be remotely disabled by the aliens in case you cease to be their friend.
• There can be a thematic relevance; for example, fission and fusion power plants, with their opportunity for radiation and accidents, are appropriate (excluding other less dangerous types) if the game is about mitigation of widespread radiation and contamination from nuclear weapons, radioactive materials, space phenomena etc.