This is a very interesting
This is a very interesting story. I am glad that you are saving money and helping to contribute to a cleaner planet. Since you mention you are paying $.19 per kilowatt you might want to look into getting solar installed. You should be able to cut your electric bill almost in half with solar. Here in California solar can be installed for $.10 per kilowatt and you get to keep the 30% federal tax credit.
I also recommend switching to LED lighting and checking out your appliances before switching to solar. It sounds like you are already well on your way to energy efficiency with passive solar. If you do install solar you might want to look into a Volt to get the most bang for your buck.