Steampunk is both science and speculative fiction set in a real or fictional era or world where steam power is still used, typically the 19th century (1801 – 1900) and Victorian era (1837 - 1901). Elements of fantasy are frequently used as well as fictional technological inventions and real technological developments like the computer occurring at an earlier date. Alternate history-style presentations of such technology as dirigibles, analog computers, or digital mechanical computers are also used and presented in an idealized light or with a presumption of functionality.
Dieselpunk is both science and speculative fiction set in a real or fictional era or world where diesel-based technology is the primary power source. It is typically set somewhere between 1918 to the 1950s with retro-futuristic aesthetics with postmodern sensibilities. Dieselpunk is sometimes divided into two themes or styles: Ottensian and Piecraftian. "Piecraftian" focuses on the aesthetics of the world wars and speculates on how human culture could cease to evolve due to constant, widespread warfare. "Ottensian" has a positive vision of technology, where humans continues to evolve unhindered by war or economic collapse.
Solarpunk envisions an optimistic future for humanity in which the primary power source is renewable energy and technology; although, it also embraces less advanced ways to reduce carbon emissions, like gardening. It uses nature motifs and is highly ornamental, ecological, and sustainable. Whereas similar genre's tend to emphasize how things can go wrong, solarpunk imagines how things can get better.