BMW i3 Driving to Net Zero Energy – Powered By Sunshine – Month 3 Update


Update Month Three – We’re killing it!

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 two cars with zero utility cost, and zero gasoline cost.

BMW i3s

BMW i3s


  • 1/4 of the way through the year, -167 kWh and a $468 credit.
  • Stats, Stats, Graphs, Graphs.
  • We’re killing it! Ready to make a projection!
  • Our French import
We estimate that we will be -$800 by Oct/Nov

We estimate that we will be -$800 by Oct/Nov

Solar PV production holding steady at 1326 kWh

Solar PV production holding steady at 1326 kWh

Electricity use for the two BMW i3's rose to 478 kWh for the month

Electricity use for the two BMW i3’s rose to 478 kWh for the month

We have a credit of $315 for the first seven months of the year

We have a credit of $315 for the first seven months of the year

1/4 of the way into our “Driving to Net Zero Energy” challenge and as they say in political election coverage:

“I am ready to make a projection and call this race.”


Projection Says It’s a Done Deal

We will be below zero in utility cost and gasoline cost providing the energy for our home and guest house, and the two cars in the garage driven a total of 24,000 miles a year. In fact we are so far ahead we will accomplish this goal four months earlier than planed with the January 2015 true-up bill from our utility.

Our natural gas cost for a year is $301.27

Our natural gas cost for a year is $301.27

We estimate at the true-up bill that we will have a credit of $400 to $450 for our electrical use and a cost of natural gas of $301 for the year thus -$100 to -$150 in total energy cost for the year.

How about total cost?

As I mentioned in my first post in May, an asterisk is required regarding the cost of energy as our utility does not let us carry over our electricity credit to our natural gas cost. Essentially our valuable peak hour electricity that we do not consume will be a gift to our utility. As the years go by we will most likely convert one or two of the natural gas appliances at the end of their useful life to electric in order to reduce the natural gas bill by using our excess electricity credit.

Where are we with energy usage and gasoline cost now compared to 2007 when we began this path to energy independence?

In 2007 our energy cost were:

  • $3,800 a year in electricity
  • $ 300 a year in natural gas
  • $2,800 a year for Julie’s Infinity G35 gasoline
  • $2,400 a year for my Volvo S60R gasoline
  • Total: $9300 a year in energy cost. ($792 per month)

This is not far off the statistical norm for a US family which uses an average of 11,000 kWh per year ($3,060 at SDG&E rates) and $2912 for gasoline according to the 2012 EPA statistics.

In 2014 our energy cost are:

  • $ 0 a year in electricity*
  • $ 300 a year in natural gas
  • $ 0 a year in fuel cost for Julie’s BMW i3
  • $ 0 a year in fuel cost for my BMW i3

Total $300 a year in energy cost. ($25 per month)
* we donate $450 worth of electricity back to SDG&E.

You can see how quickly that $9000 a year in energy cost savings will pay off a $30K Solar PV system, $15k in extra construction cost for a thick well insulated home, efficient appliances and led lights and $1000 for a EV charging station in the garage. We have calculated from the installation in January of 2007 we reached the payoff point in April of 2012.

From April 2012 and for the next few decades, we will have essentially zero or de minimus cost for energy saving us $200k to 300K in energy cost with escalating utility and gasoline cost.

How about total usage?

Julie and I live normal lives, things come up and situations change. The interesting part of our Drive To Net Zero Energy challenge is that we are real people with a real life and not some demonstration house with nobody living in it.

We have been doing really great using a net total of -167 kWh of electricity (generation vs consumption) for the first three months of the challenge. We can extrapolate the prior four months of usage pre i’3s, assuming we had the efficient BMW i3’s and the extra 1kw of solar pv production which would have saved us 225 kWh per month. We estimate that by May of next year we will be very close to a net of 0 total kWh used, +- 250 kWh per year which is a normal usage and weather variable.

The French Import.

I bet you thought it was a car 🙂

Julie and I have decided to make an impact on two young adults lives. We are hosting through Rotary Youth Exchange, a 17 year old French student named Peroline for a one year exchange. By doing so, an American young man is traveling to France to begin his year as an exchange student in France living with Peroline’s family.

Our household has now risen to four and the extra electricity that our 17 year old exchange student will use will most likely push us into the positive use territory.

Hosting a 17 year old young lady French exchange student for a year was not contemplated and is not a very good idea for the Drive To Net Zero Energy Challenge!

But life is life, unpredictable, wonderful and real. We are very happy to have Peroline as part of our family for the next year and we’re looking forward to driving her everywhere, using lots of electrons, to see the sights of our great nation.

Our goal remains Net Zero Energy usage as well as Net Zero Energy cost.  We’ll see how the the next 3/4 of the year goes.

Imagine a better future and your participation in it.

Next Month:

  • Charging stations and what’s on the horizon.
  • Our CHG emissions
  • Our version of GHG offsets

Thanks for reading and commenting.

(Past “Driving To Net Zero” articles)

Energy Challenge Introductory Article
Mid Month Article: The Energy Grid
Update Month 1
Mid Month Article: Does your Gas Station Pay you to fill’er up?
Update Month 2

*Editor’s Note: Peder is the Chairman of the San Diego County Planning Commission. His wife Julie is Director of Curriculum and Instruction at the Solana Beach School District. They have been Field Trial drivers for BMW for five years. Together since 2009, they have driven 100,000 EV miles powered from roof top solar.

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17 Comments on "BMW i3 Driving to Net Zero Energy – Powered By Sunshine – Month 3 Update"

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So does your electric only charge you per kWh?

My electric provider in NY state includes a “base charge” each month that I cannot offset with my solar production.

So while my home is closed to net zero electricity use, I still have an ~$20.00 charge every month that I cannot avoid.

For me in PG&E territory, they charge a ~$5/month ‘distribution’ fee. And that seems fair enough. And I’ll be able to cover that cost with excess PV energy generated even if sold at a measly 4 cents per KWH. $20/month is annoyingly high.

Yes, it is. The charge used to be about $16 (still high) and recently the PUC approved a rate increase corresponding to a per kWh decrease, but a base charge increase.

Which really annoys me, because in addition to making solar and alternative energy less attractive, it also takes away from low income people’s ability to manage their basic costs like electricity.

Frustrating all around.

Really wonderful. I wish i could do the same…but i am thankful that pioneers like you are ultimately going to be responsible for reducing the costs of solar cells and electric cars for rest of us….thank you so much.


I think are a little premature in calling it for such great numbers.

You started this in May (April?) at the start of the “really sunny season” here in California when you get nice full days out of your solar panels, and you only started charging the i3s during that time.

Over the winter, your solar output will go down drastically as those winter storms (we hope!) start rolling in, but your kWh will stay has as you continue to charge. You may still end up at zero, but not with the large bank you’re expecting on a one year cycle.

I was going to go to the store today. But then I saw my electric bill and it was for $105.00! And I got all panicky and called BMW to try to arrange for them to tow away my 2 $200 per month EV’s and fix me up with a couple of swell i3’s and a $40K solar outfit.

But then I looked closer and found out that the 105 bucks was for two houses and two EV’s then I was all happy and stuff and told my kids to walk to school.

Those are some sweet numbers…of course I think I burned somewhere between 3000 and 4000 kWhs just last month…welcome to Texas Summers and two A/C units.


You may want to look into so-called mini-split units, that have a SEER of ~26-27, and they use far less energy for A/C.

Nice numbers. It is difficult to extend this type of lifestyle more widely, as few have the incentive and resources to invest. But comparing apples to apples (doing what you’re doing vs. doing nothing) it is impressive to see the yearly savings stack up. I’ve done a similar accounting of changes at my house since 2010. I did a PV system and two electric cars like you, but also got rid of propane heat and we are using a ground source geothermal heat-pump instead. Overall we’re saving over $3,000/year (about $2k of that is the reduction in gasoline and electric). This is real money. Yes, there were some big initial investments, but over time this long term, positive cash flow investment will have returns better than putting money into most investments one could find, with relatively low risk and some positive social/economic impacts as well.

I’m seriously looking at buying some solar panels when I build my dream home or dream metal garage. In that unlike a lot of other silly things out there I could buy at least the solar panels would in theory feed back into the house’s expenses and off set some of them money spent on the more sillier things in the house like a 10,000 gallon fish tank and a room devoted to a giant train set.

In that if the solar panels are on the roof of the house and covering the cost of a $200 to $300 electric bill. Then in theory you could budget $80 or $100 dollars saved by these systems to go towards the cost of the train room or the large cement fish tank.

Great work Peder.. World needs more Peder 🙂