Earth Shock: which rank to use

Shaman · Nature · 7 ranks, 4 learned by level 30.

At level 30 with 45 spell power, Earth Shock rank 1 gets the most damage per mana; rank 4 does the most damage per second.

Most mana-efficient rank by gear: rank 2 up to 9, rank 1 from 10 spell power.

Every rank at level 30 with 45 spell power

Rank	Damage per cast	Mana	Damage per mana	DPS	Mana lasts
Rank 1 (level 4)	38 (37–39)	30	1.26	25.2	5 min
Rank 2 (level 8)	54 (53–55)	50	1.08	35.9	3 min
Rank 3 (level 14)	71 (69–73)	85	0.83	47.2	1 min 46 s
Rank 4 (level 24)	104 (101–107)	145	0.72	69.2	1 min 2 s

DPS counts the global cooldown. Mana lasts: casting only that rank from 1,500 mana.

Rank 1: 38 damage for 30 mana in Forever instead of 27 for 30 in Classic Era (spell power share 0.386 instead of 0.154).
Rank 2: 54 damage for 50 mana in Forever instead of 46 for 50 in Classic Era (spell power share 0.386 instead of 0.212).
Rank 3: 71 damage for 85 mana in Forever instead of 80 for 85 in Classic Era (spell power share 0.386 instead of 0.299).
Rank 4: 104 damage for 145 mana in Forever instead of 147 for 145 in Classic Era (spell power share 0.386 instead of 0.386).

From the client, for each rank: base damage or healing and its range (SpellEffect base points and variance), the extra per level up to the rank's max level, the spell power share (coefficient), mana cost, cast time, duration, global cooldown and cooldown.
No downrank penalty in the Forever client. Classic Era's client puts a penalty for spells learned before level 20 inside the coefficient (Shadow Bolt rank 1: 0.14); Forever's client gives the full share (0.486), for 80 low-level ranks across the classes. Anything else would be on Blizzard's servers, so the calculator shows Classic's rules only as Speculation.
Speculation: crits count only on direct hits, at 150%, as in Classic; the example gear (1.5 spell power per level) is not client data.