Reka, thanks. I was talking cheaper relatively. At the airport P51 has parking charges of 78CHF per week. I was not able to find out on Balexert's website if their charges will be any better. I certainly need a covered, guarder parking, esp in this weather.  

Dear Funinsun,

Can you find a friend to drop you off at the airport? That would solve your problem. Or get a taxi?

If these are not options, then it would probably be a better idea to find parking on the french side. Reka is right in saying that there is no such thing as cheap parking in Geneva LOL.

Try parking in the Ferney area - like the shopping areas in Ferney Carrefour market or near the Ferney-Voltaire Mairie (at the school carpark - school holidays will start soon). They are free..!

Then take the Y Bus, this is the schedule:

http://www.tpg.ch/en/horaires/rechercher?p_p_id=PlansReseaux_WAR_PlansReseauxportlet&p_p_lifecycle=0&p_p_state=normal&p_p_mode=view&p_p_col_id=column-1&p_p_col_count=2&_PlansReseaux_WAR_PlansReseauxportlet_jspPage=%2Fhtml%2F_thermometre.jsp&_PlansReseaux_WAR_PlansReseauxportlet_req=thermometre&_PlansReseaux_WAR_PlansReseauxportlet_ligne=Y

I'm not sure if you can park at the underground parking at carrefour though since they also close their gates at night and might notice your car there especially when it will be there for 3 weeks.

But please, I can't guarantee your car will be safe, it's just like leaving it in any other place really (whether its paid parking or not).

Something for you to consider... Good luck!