Searching around, people say that the saving throw DC of a wand is based on the minimum stats required to cast the spell, but I can't find such a statement in the SRD. Can someone confirm?
Wands follow the general rules for Saving Throws Against Magic Item Powers on the page on magic items (emphasis mine):
Saving Throws Against Magic Item Powers
Magic items produce spells or spell-like effects. For a saving throw against a spell or spell-like effect from a magic item, the DC is 10 + the level of the spell or effect + the ability modifier of the minimum ability score needed to cast that level of spell.
Staves are an exception to the rule. Treat the saving throw as if the wielder cast the spell, including caster level and all modifiers to save DCs.
Most item descriptions give saving throw DCs for various effects, particularly when the effect has no exact spell equivalent (making its level otherwise difficult to determine quickly).
Staves are explicitly called out as an exception to this rule, but wands are not.
The saving throw for a Wand is 10 + Spell level + the Minimum ability score modifier necessary to cast that spell.
So if you're working with a Wand of Fireball, Fireball is a 3rd level spell, which requires a 5th level Wizard to cast with an ability score of at least 13. The modifier for a score of 13 is +1. So the save of a Wand of Fireball will be (10 + 3 + 1) for a total of DC14.
This can be found in the section speaking about Magic items, under where it mentions saving throws for magic items.