[Spaceships] Reasonable numbers for Refinery Systems / 'Artificial' Fuel?

[vicky_molokh]

Greetings, all!

Okay, the official refinery rates are weird, producing (at SM+5) a half-tonne of rocket fuel per hour, which is way more than is required to run the refinery using same fuel.

But! While this used to be a fuzzy area, I'm planning to officially declare that my setting has a common practice of synthesising a fuel from ubiquitous components when there's abundant energy.

Perhaps the simplest way to make sure it doesn't run out of control is to see how much energy can be gained from the given amount of fuel, and declare that it takes twice as much energy to synthesise it. That means that if a fuel cell (1 Power Point) can work for 24 hours on a tank of fuel, then it takes 2 Power Points to produce one fuel tank of said fuel (over same duration; 1 PP if working over 48 hours etc.). But perhaps there is some reason these numbers don't make sense.

My intent is to make sure that fuels are an option, not a must-have, when pitted against batteries. (TL6+3^ batteries; can provide up to 2 Power Points over up to 6 hours, and can recharge from any power source, with no spontaneous discharge, no risk of explosion, and ability to be safely recharged thousands of times at the very least.)
At those numbers, IMO, fuel-powered (motorised) yachts still make more economic sense than battery-powered ones (because you need more endurance), but ornithopters and semi-reactionless* (0.5G per PP) aircraft can easily get by on batteries, since those are easy to recharge and rarely, if ever, need to stay in the air for more than 6 hours at a time.

So, cost of fuel seems like a prime balancing factor. Making fuel requires a refinery module, a power source, access to raw materials (cheap, you still need to have them right here now), and of course a place to store fuel and refuel the clients. Logistically, fuelwork seems pretty complicated compared to essentially reselling electricity.
So, what are reasonable price ranges for a fuel that is synthesised from ubiquitous components in a manner described above? How are they likely to compare to prices of raw power?

Another issue is the balance of jets against MPDs. But since a single fueltank is enough for 1 hour of jet flight, while a single battery can power two MPDs for 3 hours, things seem okay. (Jets are still better in terms of maximum acceleration per unit mass.)

Thanks in advance!

* == Mono-Polarised Displacer. Essentially, a more expensive variant of a unidirectional magnetic planetary drive, but with no side effects whatsoever. Also works in space, somewhat.