In an old campaign of mine, we sacrificed Power for specific runes from the god worshipped and those runes could then be used to call for rune magic, see snippet below from the rules we used. What I liked about this solution was that it made sense to seek out a larger site if possible for increased chance of success, improved for a holy day and even more for the high holy day, and also with additional bonus possible for a critical, or penalty for a fumble!
The day following use, or later, Rune-power can be restored by the god that provided that particular Rune.
An initiate can once per season attempt to regain his Rune-power used to cast reusable Rune spells by attending a successful Worship Ceremony. A priest (i.e. a character with full investiture) can in a sanctified location on any day following the use attempt to regain a single Rune-power used to cast reusable Rune magic spells, through the successful use of the Ceremony ritual, only one attempt to regain a Rune can be made per day.
If the attempt to regain a Rune-power used to power a reusable Rune magic spell fails, a new attempt can be made next day for a priest or next season for an initiate.