Adding a fan will not increase anything in power related except the minor amount of additional current it is going to be needing from the battery to run it. I typically do not like running fans on my RC's because they are prone to failing at the worst times and they are $5 to replace at the cheapest I've seen. They will, however, help keep electronics within safe operating temperatures in summer heat waves. If you need a fan to keep your electronics cool in the winter then you need to change your gearing.
I believe it is a mistake to say heat creates resistance but that's another thread topic entirely.