Hi Terry D - I'm out east in Manitoba and out here a heater/defroster is required to defrost front windows, however there is a caveat that states open cockpit vehicles do not need one. Essentially you are at the mercy of the interpretation of your inspector. I installed one and have actually had to use the defroster a couple of times and yes it does make a difference.
Probably not the clear answer you are looking for but just thought I'd throw it out there.