Pokemon attack powers

Question

If I had an electric Pokemon knowing Thunderbolt (pwr: 90) and Ancient Power (pwr:60) and was facing against any pokemon except where electric does x0 damage, would Thunderbolt "always" be the better move unless I can get x4 damage with the rock move? (Ancient Power is a Special rock type move)

My logic is: Thunderbolt gives STAB so the effective power is 180, so even if I was fighting a Pokemon who is weak against rock, that would only bring the power to 120 where as the Thunderbolt would still be 180.

Are my calculations correct? Thus making it so Thunderbolt is the preferred move at all times unless facing ground types or where rock can do x4 damage?

Answer 1

Well, as discussed in the comments, the first thing to consider is that STAB brings thunderbolt to 135 rather than 180.

Second, there are more type combinations to consider than just those that result would give rock a x4 multiplier. Especially considering rock and electric share a x2 against flying.

Times when using Ancient Power is more effective than Thunderbolt (used by an electric type):

Immune to electric (x0)

Ground or Ground/anything also Lightning Rod

While rock isn't good offensively against ground either (x0.5) - ground is completely immune to electric. As is any Pokemon with the Lightning Rod ability. Lightning rod may also affect your usage of Thunderbolt in double or triple battles, if one opposing Pokemon has Lightning Rod, you do not want to use electric against either target.

Super resistant to electric (x0.25)

Dual types of consisting of two of (Dragon/Electric/Grass)

This category is rare. As there are no Dragon/Grass Pokemon, the list here is made up entirely by Mega Ampharos, Zekrom, and Rotom(Mow). Although rare, these three would effectively reduce Thunderbolt's power to ~33.75

Resistant to Electric (x0.5) and weak to Rock (x2)

Any dual types that combine one of (Dragon/Electric/Grass) with one of (Bug/Fire/Ice)

Paras, Parasect, Wormadam(grass), Sewaddle, Swadloon, Leavanny, Joltik, Galvantula, Mega Charizard X, Rotom(heat), Rechiram, Snowver, Abomasnow, Rotom(frost), Kyurem.

In this Category, Tunderbolt's power would be 67.5 vs Ancient Power's 120.

Double effective Rock (x4) and neutral to electric (x1)

Dual types of consisting of two of (Bug/Fire/Ice)

Larvesta, Volcarona.

Another rare category, made up entirely by the two Bug/Fire types. Here Ancient Power would do 240 vs Tunderbolt's 135. This category does not include the Flying type, as flying is also weak to electric which would cause thunderbolt to jump to 270.

Answer 2

To answer the base question, by multiplying the Base Power (BP) of a move you can determine when a move will be more effective than another based on type effectiveness.

Simply compare the BP of two moves then consider whether you get Same Type Attribute Bonus (STAB) (x1.5), whether the opponent resists or is weak to the move (x.25 for double resist, .5 for resist, x2 for single super effective, x4 for double super effective). Due to STAB you do indeed want to mostly pack moves that cover types that your STAB type(s) aren't super effective against.

So generally if a move is going to hit for neutral damage, a non-STAB move will have to have a base power over 1.5x the BP of your STAB attack. More relevantly, you should generally keep one of eacH STAB attack and then non-STAB moves that are SE or neutral against types that your STAB moves aren't.

You can use this calculator to see your type coverage.

Of course, this ignores secondary effects; sometimes those will be relevant over the base power. So you might prefer a priority move like Quick Attack to get in a weak attack to KO a faster opponent before they can get in one last hit.