cook stove gas pipe

I need a new stove. Kitchenaid cooktop with a grill calls for 3/4" gas pipe, but what I have is 1/2" and repipe will require breaking some slab.
This stove has 20, 10, 5K btu burners and 18K grill. With 1/2" gas pipe, do I get less btu (smaller flame?) or one or more burner or grill just not working?
Thank you in advance.