Solar Power
Increases Special Attack to 1.5× but costs 1/8 max HP after each turn during strong sunlight.
Full effect
During strong sunlight, this Pokémon has 1.5× its Special Attack but takes 1/8 of its maximum HP in damage after each turn.
In game description
In harsh sunlight, the Pokémon's Sp. Atk stat is boosted, but its HP decreases every turn.
Pokemon with Solar Power
Using Solar Power in Cobblemon
Abilities are passive and always active, so Solar Power costs you nothing to run. If it is marked hidden on a species above, expect it to be harder to obtain: servers differ in whether hidden abilities come from breeding, an Ability Patch, or events.
See the Pokedex for which abilities each species can have, and IVs, EVs and breeding for how to actually pass one down.