It has been suggested by my contractor (they don't install them) that a PFC would save on energy costs associated with heating/air conditioning systems and other household, motor driven appliances.
Information on the web is highly technical so I couldn't get too good of a grasp on their workings.
Basically, as I understood it, PFCs tend to deal with the reactive component of current, rather than the resistive part.
Other than that, I'm kind of in the dark.
Hoping the PROs can address this in terms of savings, effect on startup vs continuous run, and degree of surge protection (if any).