The Wizard Edge reduces the cost of a power by one point for each raise. Does this reduce the Power Points per round used, if you roll a Raise or Two Raises using their Arcane Skill roll?
I was curious about this, and did a search on the official PEG forums. Since I didn't find anything I posted the same question and came up with this offical response from Clint. Basically, it only affects the cost of the initial casting.
In Mass Battles I believe the answer using the rules as written would be that the Wizard Edge does not affect the Power Points used because of the battle rules' abstract nature. This would make sense because the battle rules don't allow for use of specific spells for example.
It is similar to questions about whether a character's healing skill can be used in each round or not, and there are a number of discussions/questions about this on the official forums. Whenever this type of thing comes up the answer is usually that it is up to the GM to make a call. You might allow the character a different roll for the overall number of power points used per round so that the average number of points used is less; how about 2d6-d4, where the d4 represents how many raises they rolled over the duration of a particular round?
You need to be careful with the idea of giving a 'discount' for having the Wizards Edge though. For example, if it applies here, then why shouldn't shooters with Marksman get a discount to the number of bullets used? Or take it even further - the higher the shooting skill, the less bullets you need to take someone down. What I'm trying to say is that I would be careful to try and retain the abstract nature of the Mass Battle rules if at all possible.