If combined with an Attunement, using this glyph to cast a spell costing 15 or more energy will result in a net gain of energy.
If preceded by Auspicious Incantation, you will gain energy proportional to the original spell cost. This can net 40 energy or more at high ranks of Inspiration Magic.
The only way to take full advantage of this skill at Energy Storage higher than 9 is to be under the influence of Quickening Zephyr and/or the environment effect Veiled Nightmare.