The Creating New Races rules are quite comprehensive and I think trouble in trying to value something like being able to summon a weapon is expecting an ability to appear almost exactly like that as a Racial Trait. What you describe sounds more like a spell which you can have as a Racial Trait, I'll point you to the Magical Racial Trait, Standard "Spell-Like Ability, Lesser" of the Creating New Races rules that were linked above:
Spell-Like Ability, Lesser (Variable, see Special)
Prerequisites: None. Benefit: Choose a 2nd-level or lower spell that
does not attack a creature or deal damage. Members of this race can
use this spell as a spell-like ability once per day. The caster level
of the spell is equal to the user's character level.
Special: This trait costs as many RP as the level of the spell chosen (minimum
1RP). This trait can be taken up to three times. Each time you take an
additional spell, adjust the RP cost of this trait appropriately.
This is how you should calculate such a racial ability LIKE summoning some sort of energy based weapon. Look through all the spells of all the caster classes and look for any spell which replicates close enough the effect you had in mind. And the rules for duration of that spell and how much this spell-like-ability costs will tell you how it is balanced.
I don't know what spell that might be, perhaps Umbral Weapon? This ability could just exist exactly as the rules say it is, as a spell-like-ability.
Remember, spell-like-abilities still lack most of the qualities of a spell such as somatic/verbal/material components or armour % fail chance, you just have to make a concentration check and they provoke to cast.