The BMW i3 & Light Bulbs. A Connection In Watts.

In modern homes, there can be well over 100 light bulbs inside and outside.  Gone are the days of one light bulb in the middle of the room, or one lamp fixture with one light bulb, or one porch light.   Today’s new homes feature architectural recessed lighting with several fixtures in a room and  lamp fixtures with multiple light bulbs.   Outdoor areas can become lighting masterpieces with dozens of lights in both the front and back yards set on timers illuminating for 2-6 hours per night. 

For kicks I counted the fixtures just in our homes master bath.  2 sets of vanity lights with 4 bulbs each over each sink, 4 recessed can lights, 2 recessed cans over the tub,  1 recessed can in the shower, 2 recessed cans in the lavatory, 1 light fixture in the lavatory fan fixture and 4 in the walk in closet. That’s 22 light bulbs in our master bath area alone!

Now shifting gears (that’s a bad metaphor because you don’t shift gears in an electric car) to the new BMW i3.  The BMW i3 is an extremely efficient, beautiful and fast electric car that Julie and I will be driving in several short months following on the heels of our great four year experience as field test pilots with the BMW Mini-E and the BMW ActiveE electric cars.

The BMW i3 will be highly optimized for efficiency by utilizing light weight aluminum and carbon fiber in its manufacture.  This optimization will result in an average of around 5 miles traveled per kilowatt of electricity used or 5 mpk.   If an average driver in the i3 drove 12,000 miles a year, they will use approximately  2,400 KWh per year.

The BMW i3  will use exclusively LED lighting both for interior lighting as well as for exterior headlights, brake lights and turn signals.  Which brings my thoughts back to the home.  What if like the BMW i3, a home used exclusively LED lighting  both inside and out?  How much energy could be saved?

Using a modern home and our lifestyle as an example, I would estimate that a 1/3 of those 100 light bulbs are on 4 hours a day,  1/3 are on 2 hours a day  and 1/3 are seldom or never on.   For an average of all the bulbs, I would say two hours per bulb is fair estimate (your family or home may vary.)   That gives us 200 bulb hours per day.   Assuming an average bulb rating of 60 watts,  We consume  12kwh a day, 360kwh a month, or 4300kwh per year in lighting  a modern well appointed home.

What if we switched those to LED like in the BMW i3?

The 60 watts that an incandescent bulb used would be reduced to 8 watts using an LED.  The 200 bulb hours a day for our modern house would now be reduced from 12kwh per day to to 1.6kwh per day, 48 KWh per month, or 585kwh per year.   That’s a savings of 3,715kwh a year switching from 60 watt  incandescent to LED.  

Needless to say the savings of 3,715 kwh a year is more than 150% greater than the usage of the 2,400 kwh a year used by the BMW i3 to drive 12,000 miles a year.    

The bottom line….. change the most used incandescent light bulbs in your home and save more than enough energy to power your BMW i3 electric car…forever.

My advise……Only change the bulbs that you use most often.  No need to change the bulbs that you seldom or never use.  Appliances, TV’s. DVR’s and cooling are other areas that you can save additional electricity. 

Drive for  less total energy after changing out your light bulbs...That’s a bright idea.


Authors note, (older, smaller homes or apartments will use considerable less lighting than this example.  Larger homes and estates can easily use triple this amount of energy for lighting, so results may vary,  If you have already made the switch to LED’s thank you.   Modern LED’s are available at your local hardware store and Costco in many popular sizes for $7 to $25 a bulb.)