There’s a secret “stealth mode” which allows Prius owners to put their cars in all-electric mode. While it’s not functional in the USA, it does work in Japan and Europe. Some Prius hackers have already enabled the button and added an extra battery. There’s a bit about it here and you can order the kit here ($45). If you’re willing and able to do this on a 2004-2005 Prius, please let us know- we want to feature this in an upcoming issue of Make! email, AIM/iChat or Skype me.