So, I just started up a sci-fi game, and each player got to declare something, and one of them declared that energy was expensive and scarce, so we came up with a really simple outline for how to track how much energy your spaceship has, and how much energy things cost. So as not to confuse spaceship energy with ENERGY effort, we call it YU for “yog units” (thank you skuk). Here’s the basics:
A basic small ship starts with one of YU. An FTL hop from one destination to the next uses 1d6 energy.
Recharging small devices/light weapons is 1 YU. Large devices, light vehicles, and heavy weapons is 2 YU.
Escaping the gravity well (leaving a planet’s surface, or moving away from the center of a solar system uses 2 YT; traveling from the outer part of a system to the inner goldilocks zone costs 1 YT.
Stargates can save energy on interstellar travel, and space elevators and skyhooks can save energy leaving planets and traveling to the outer end of a system respectively.
From there you can apply this simple economy to all sorts of things pretty easily.