Quite a bit, I’d say. To understand why, check Richard J. Evans' In Defense of History (http://www.amazon.com/Defense-History-Richard-J-Evans/dp/0393319598/ref=sr_1_1?s=books&ie=UTF8&qid=1457932994&sr=1-1&keywords=in+defense+of+history)

While historians, concerned as we are with a rigorous devotion to what a given piece of evidence says about the past “as it actually was,” might not be willing to go as far as Foucault’s criticism of history itself as an exercise of power (Evans 169), his insights have certainly left a lasting impact on our field. As Evans went on to say, “the Foucauldian linkage of power and knowledge went together in the 1970s and above all the 1980s with the rise of explicitly politically committed forms of historical writing and research…the point of historical discourse, [the argument went], was to empower people—specifically, to empower the particular group or groups of people [the historian] represented.” (170)

The amount of emphasis placed on this approach has changed as time has gone by, of course, but Foucault did encourage historians to think about the relationship between power, historical truth, and how oppressed groups (in terms of race, gender, economics, etc.) might not be justly represented in what used to be commonly considered proper history. It is advice we have generally kept in mind.