Resist energy question

[Blake Duffey]

Per the SRD:

This abjuration grants a creature limited protection from damage of whichever one of five energy types you select: acid, cold, electricity, fire, or sonic. The subject gains resist energy 10 against the energy type chosen, meaning that each time the creature is subjected to such damage (whether from a natural or magical source), that damage is reduced by 10 points before being applied to the creature's hit points. The value of the energy resistance granted increases to 20 points at 7th level and to a maximum of 30 points at 11th level. The spell protects the recipient's equipment as well.

Is the energy type (acid, cold, etc.) chosen at memorize time? Or at casting time?

[Remco Sommeling]

It is chosen at the time you cast the spell, though I have seen it houseruled otherwise in low magic settings specifically.

[Blake Duffey]

Remco Sommeling wrote:

It is chosen at the time you cast the spell, though I have seen it houseruled otherwise in low magic settings specifically.

Based on the description, I tend to agree. I think it may have been different in a previous edition of D&D?

Thanks for your input.