The very idea of a galactic energy mix makes very little sense, in no small part because it is impossible to share energy production between planets or star systems. While it would be technically possible to produce galactic statistics pertaining to energy production on human planets, the sheer variety of planetary settlement types and power needs would make this endeavour absolutely meaningless. What can be done, however, is to identify various types, or profiles, of planetary energy mixes in human space.

The single largest energy mix is to be found on Earth, home to the vast majority of humankind. The terran energy mix (fig.1) is the result of a long and complex history, marked by the collapse and subsequent reconstruction of human power networks in the Low Age. Though nuclear power sources (fusion and fission) represent up to 40% of this mix, the relative political fragmentation of the Earth and the bottom-up communal structure of its superpowers have prevented these complex, centralized power sources from becoming prevalent. Fusion and fission thus play a crucial support role, providing a centralized baseline of power that acts as a safety net for the wide variety of renewable energy sources that power the Earth's communities. The key word, as usual with everything Earthbound, is diversity. No other planet relies on such a complex energy mix profile.

Energy mixes built from the ground up on recently settled worlds are on average much less diverse, and skewed towards specific technological choices made by the first colonists. Elora is a very good example of this phenomenon (fig. 2). Fission is virtually absent on Elora, with the planet's very strong baseline of permanent power relying on fusion plants (often deriving from space-based cores) backed by geothermal and orbital solar stations. The rest of the energy mix is adapted to the planet's oceanic nature, with one fifth of local power generation coming from Elora's strong currents and tides. This is the young prosperous colony type.

Large stations like Irenia's capital of Phi Clio (fig. 3) have very stereotypical energy mixes, with an over-prevalence of fusion power, often built in two waves -- one at the initial station deployment (station cores) and one later down the line (additional cores). The rest of the baseline is covered by Lagrange-stabilized orbital solar stations, especially in the energy-rich Pleiades region. This is the station type.

While fusion/fission baselines are present in most energy mixes, some of them have decided not to include them, the most interesting one being Mundis and its purposefully lower-tech energy mix (fig.4), that almost exclusively relies on intermittent power sources that balance each other all year long. Wind power on Mundis is used both to generate electricity, or to provide mechanical energy to factories and devices directly -- effectively replicating the 18th century windmill economy. The local gas giant of Iteren also provides a small amount of beamed power to top off the planetary energy mix when needed. This could be considered as the full intermittent type.

The snowball type is found on cold planets and often shows a prevalence of fusion/fission and geothermal power sources. Smyrnia (fig.5) is the largest planet with this subtype, though its anarchic nature makes fission deployment impractical, while geothermal power only requires to drill through the ice. If Smyrnia was more stable, the ratio would probably be reversed. 

On the other end of the spectrum, tidally-locked planets follow the renewable baseline type, as the presence of a permanent terminator between the night and day sides effectively mean otherwise intermittent power sources become permanent -- hence the somewhat surprising prevalence of wind power in the energy mix of Ishtar, backed by fusion and a puny quantity of solar power, struggling under the local red dwarf. 

Waterworlds obey to a similar logic, with the ocean world type of energy mixes, relying on thermoelectrical devices leveraging the temperature differences between the surface and the abyssal regions as well as tidal power, both being extremely reliable and almost permanent power sources on waterworlds.