Power Casting

Power Casting is a leveled perk found on page 29 of GURPS Thaumatology: Magical Styles
Given its sole use is to add to Magery for a single missile spell for the sole purpose of depending how much energy can be pumped into it for damage, it can be compared to Magery (One Spell Only -80% see One-Spell Magery) which costs twice as much, but has the benefit of higher spell level which in addition to Power Casting:
:1) makes the spell more likely to succeed (particulary in low or very low mana, or when suffering penalties from shock)
:2) allows reduced Ritual requirements, allowing it to be cast without gestures or with FP reductions
GURPS Magical Styles: Dungeon Magic (pg 17) made this a key component of the Order of the Sun's Thaumatergetics style. Since their key focus is on big booms (but they like to shout loudly) buying up the energy that can go into it instead of buying up the magery makes more sense for them.
MS:DM also added something absent in T:MS: the Energy Orbs on pg 19. Since the energy they store depends on how much can be pumped in, Power Casting would help with this new option.
Unlike MAGERY however, it wouldn't help buy off the expensive skill penalties.
Category:Perks