Our one year experiment of living and driving on sunshine is over!

The idea is a simple one.

"Harvest endless sunshine from a small portion of a roof to provide 100% of the energy needed to power a home and the two cars in the garage, with zero utility cost, and zero gasoline cost."

On May 15th, 2015 we concluded our year long Driving to Net Zero Energy Challenge.  It's hard to believe that our two BMW i3's are already a year old and boy did time fly!  I'll have an overall wrap up post about the year on June 1st.

Before then,  I'll carve out a couple of sections and focus a little more in depth on various parts of the effort.

We believe we are the first household in the world to attempt this with full documentation.  We also believe that there are dozens, perhaps hundreds of other households who have accomplished the exact same thing without going though the painstaking detail and very public process of sharing private and personal information.

Thank you to BMWi, ChargePoint, Stellar Solar and SDG&E, for following us and supporting us during this past year.  It is because of a very efficient home, a great Solar PV system (installed in 2007) and the BMW i3's, the most efficient cars sold in the USA, that we were able to attempt this effort.

We have also documented this effort at every turn, with our utility, our Solar PV generation, and with the ChargePoint CT 4000 charging station in the greatest detail possible. With the ChargePoint CT 4000, we are able to account for every kWh taken from the wall and used for the BMW i3's.

Data is king,  ChargePoint with the CT 4000 and soon their residential home charger the ChargePoint Home, allows the owner to see data on each charging session in detail, just like checking up on your bank account or your friends on Facebook.

A focus on the BMW i3's powered by Solar PV. 

Our BMW i3's in the garage

We're loving our BMW i3's and they have been a joy to drive all year.  They have been trouble and maintenance free with the exception of one service visit for each car to update the software and replace the KLE.

The cars are a blast and spirited to drive, especially off the line,  and are very practical for our semi-urban lifestyle.  Every morning they await us with a full charge ready for the days adventure.  One detail in particular that has been very impressive is that we have no door dings, dents or scratches after a year of duty on the roads.  Typically for us we collect a few door dings and the occasional scratch every year.  The carbon fiber construction and thermo-plastic skin appear to be a great advance in not only lightweight construction, but also in durability and appearance.

Just one funny anecdote.  Of course we race our cars against each other! Julie and I both have the BMW i3 bev model, so we have to see who's got the fastest car.  In the first race Julie beat me by a long shot and  I was sure that BMW had made her car just a little faster than mine.  We swapped cars and did the same race again...and Julie beat me by a long shot.   I have concluded that my extra 150lbs was the difference in both races :)  Julie may be able to go 0-60 in 6.5 seconds, but it takes me a few ticks longer.

Using our stats we collected every month for the past year, here is in detail how our cars performed powered by Solar Energy. That's the beauty of the challenge. These are all actual and real world numbers, not estimates or calculations.
Location is Carlsbad Ca. 

• A total of 5061 kWh of electricity was used to drive 21,477 miles in two BMW i3’s.

• Julie averages 4.3  miles per kwh  11,862 miles / 2717kWh

• Peder averages 4.1 miles per kwh  9615 miles / 2344 kWh

• Our 8.5kw Solar PV system generated 13,546 kWh for the year. This equals 1593 kWh per kw system size

• A 3.18 kw Solar PV system (3.18 times 1593) would provide the 5061 kwh of power for both BMW i3s driven 21,477 miles.

• 37% of our overall solar generation was used by our BMW i3’s,  63% was used by our home

• It would cost $9540 to provide the solar supplied energy to drive both BMW i3's and subsequent cars, for 25 years (536,925 miles) 

• Two gas cars @25mpg (average fleet mpg) would use 859 gallons of gasoline to drive 21,477 miles

• Current cost of gasoline in San Diego Ca is $3.93 a gallon using 859 gallons of gasoline  is $3375

• The total cost of the PV System is equal to buying gasoline for 2.82 years.  An ROI of 35.4%

• Driving the BMW i3’s powered by Solar PV, the cost per mile is $0.017  cents per mile.  

• If advantageous TOU rates are factored in,  the Solar PV system size and cost would be reduced by 22%, the cost per mile would be $0.013 per mile.

• Driving on Solar PV supplied electricity is 1/10^th the cost of driving on gasoline.

Average price of gasoline on 5/22/15

You can live and drive on Sunshine :)

Cheers and thanks for reading and commenting.