For what it's worth I prefer simple re power and fuel. Not quite as rigidly simple as some the rules but not as involved as others either.
Basically there are two big power users on a starship. The jump drive and the maneuver drive.
Jump drive - Power plant must match or exceed the rating of the jump drive and be providing that level of power throughout the jump. Yes, that is what keeps jumpspace from ending your trip before you reach the exit. Loose the power plant while in jump, you die. Run out of power plant fuel while in jump, you die. In MTU at least. The only fuel savings available in this area is if for example you have a P2 and J2 but engage in a J1 allowing you to throttle back the power plant to a P1 at a like reduced fuel consumption for that trip.
Maneuver drive - Power plant must match or exceed the rating of the maneuver drive and be providing that level of power while in normal space for the safety and comfort of the ship, even if not under acceleration. The M drive also includes/incorporates the inertial compensation (automatically dampens all drive thrust*) and the (magic
) shielding that protects from background radiation and small mass impact collisions. A ship may save fuel by throttling back the power plant to match the currently engaged maneuver drive level, for example a J3, M1, P3 ship exiting jump space can drop from the P3 level of fuel burn used during its 3 parsec jump to just P1 for maneuvering safely in normal space.
* note - does not dampen all acceleration from outside the hull, such as local gravity or impacts, these still act on the hull and may be felt inside the hull, a hit by a missile or debris will be felt, landing of a world will transfer the local gravity to within the hull but may be compensated by the artificial gravity
A few other significant power users are:
Artificial gravity - minimum P1 to maintain (P = G) but feeds off the flow to Maneuver or Jump (as long as the appropriate drive is functional, and at up to the current operational level).
Energy weapons - requirements vary and are in addition to Maneuver drive.
Defensive screens - requirements vary and are in addition to Maneuver drive.
Electronics - advanced computers/electronics also require additional energy.
By applying points to the power systems one can permit some management choices, like forgoing energy weapons fire to divert power to shields.
And because I like my space sci-fi with a submarine warfare quality (yes, there is no stealth in space, but... ) I also allow silent running. The power plant is shut down and the ship runs minimal systems on battery power. The power plant provides for/includes battery backup for minimal systems to operate for 1 week per rating, or 1 turn per rating at full power (though that creates the same signature as running at full power). Minimal systems are low life support (minimal heating and air) and low lighting. There is no power for maneuver or jump naturally. Nor artificial gravity, inertial compensation, protective shielding, energy weapons, defensive screens, or advanced electronics. All excepting the surprise use of full draw on the battery/capacitors, which not only fully drains but damages them. It is a handy surprise tactic though, or a last ditch save option in a crash for example.
Two minor flaws (features
) in this method are:
The introduction of J0, aka microjumps. I'm not really comfortable with the idea (it doesn't always fit my take) but it has been there for ages. Treating it as a short plotted J1 works, which is the usual method.
Misjumps. Being hurled into level 12 jumpspace when you only have the protection of a P2 is bad. Of course that's the risk one takes for cutting corners. Jumpspace bleeds through the insufficient protection but because there is some protection you might not die. Maybe you just get badly "burned", like going to the beach with SPF-5 on a day when the UV rating would call for SPF-30. Only this burns your mind too.
