In the Auran Empire campaign setting, we presume the existence of a "psychic energy" which is used to channel and fuel spells. Clerics and mages use their personal psychic energies to initiate and channel spells, while the actual psychic energy to fuel the spell comes from gods (clerics) or latent elemental energy (mages) respectively. The system ties into the Divine Power section in Chapter 7 of ACKS, which shows how much "psychic energy" a person generates when sacrificed, or per week of devotion.
On this basis, I was able to put together a spell point system for ACKS, for those of you who enjoy such things:
Spell Level: Cost in Spell Points
1st Level: 1 point
2nd Level: 3 points
3rd Level: 6 points
4th Level: 10 points
5th Level: 15 points
6th Level: 21 points
Cleric Spell Points Per Level
Mage Spell Points Per Level
If any of you test the system, let me know.