Saturday, August 14, 2010

How many light bulbs does it take to plug in an electric car?

I’m having a blast driving Mini-E # 183 now in my 14th month with almost 19,000 miles on the odometer.
The car has been rock solid with no mechanical problems and the fun factor of driving the little electric pocket rocket continues every time I fasten the seatbelt. Overnight trips are becoming common to favorite hotels and destinations where charging infrastructure exist. Gas cars are starting to resemble the steam locomotives of the late 1800s.

So I got to thinking last night, how many light bulbs does it take to plug in an electric car?

Think for a moment of the power required to move a 3,000lbs car like the Mini-E, or Nissan Leaf through the urban and suburban jungles of the big city for 12,000 miles a year. Freeways, parkways city streets and parking lots, all traveled in the normal course of a year’s driving for most Americans.

If powered by traditional gasoline engines we could all do the math fairly easily. For a 20mpg car it would burn 600 gallons of gasoline weighing 4,800lbs costing $1,800 a year. For a 30mpg car it would burn 400 gallons of gas weighing 3,200lbs costing $1,200 a year.

For most typical drivers, that car in your garage ignites, explodes, burns and exhausts its way through 4,800lbs of refined gasoline (most of it imported) every year in order to power the car for 12,000 miles.

Simple (or incredibly complex) enough so far.

But how about the electric car?

Driving around Newport Beach the other night at 0- dark hour and seeing all the light bulbs on in storefronts, art galleries, light poles, signage, and parking lots and just about everywhere, I thought to myself, those light bulbs run on the same octane as my electric car. I wonder how many light bulbs does it take to plug in an electric car? Or more accurately stated, How many light bulbs will the electric power needed to drive my Mini-E for 12,000 miles illuminate?

The answer I came up with was shocking! Please double check my math and tell me I’m wrong because even I don’t believe it!

Drining Mini-E #183 for 12,000 miles requires the same energy to Illuminate exactly four standard 100 watt light bulbs for a year. Or stated another way, it takes four light bulbs to plug in an electric car.
Four light bulbs!

The math works like this,

Four 100 watt light bulbs illuminated for 24 hours would use 9.6 kwhs of electricity. This multiplied by 365 days a year equals 3,504kwhs a year to illuminate those four light bulbs.
The Mini-E gets 3.5 miles per kwh. 3.5 miles multiplied by the same 3,504kwh used by the four lightbulbs equals 12,264 miles. For the Nissan Leaf which gets 4 miles per KWH the miles climb to just over 14,000 miles.

If 100 watt light bulbs were just illuminated for 1hour a day the power needed to drive an electric car 12,000 miles a year would equal the electricity used by 96 light bulbs.
Four, 100 watt light bulbs illuminated for the year, or 96, 100 watt lightbulbs illuminated for one hour a day for a year.

Think how many billions of high wattage incandescent bulbs that we are shifting to CFL and LED lighting saving 70% to 80% in energy usage.

Lighting Four light bulbs uses the same power as driving an electric car for 12,000 miles.

The future is indeed getting brighter, and much cleaner.
Oh, and the answer is zero, Light bulbs don't plug in electric cars.
Ha Ha!

Mini-E #183, 18,875 miles.


  1. Great Post Peder! It's something when you break it down like that. How many people waste electricity by leaving a light on unnecessarily because "It's just one light bulb". It would be easy to save enough energy to power your EV just by paying more attention to your home energy usage. However you really can't "cut down on your gasoline use" unless you drive less. I like the topic, I think I'll do a blog post on this in the future. Thanks for the idea!

  2. Tom,

    Thanks for backing me up in the comments section of the examiner interview!

    I'm pretty sure most people could pay for their electric car energy use just by being a bit more energy aware at home.

    3 years ago we changed out about 70, 50 watt halogen bulbs in recessed 4in cans with a completly dimmable 8 watt ccfl bulb from litetronics.

    These bulbs are working great and I have only replaced 4 out of 70 in 3 years.

    That savings alone (42 watts times 70= 2.94KW per hour. averaging 4 hours a day thats more energy saved than I use in the Mini-E.

    When you get into appliances the savings can be even more dramatic.


  3. Very interesting analogy! While every light bulb matters, and people absolutely should be turning off lights they leave on for no reason at home, and elsewhere, for most American homeowners, there are three areas where doing just a little, could save a lot of electricity (and money) which could then be used to power and electric car.

    1. Reducing the use of home central AC (turning up the temperature a few degrees), and/or "toughing" it out a bit (go ahead, live dangerously and try to survive with an in-house temp of 77, 78, 79, or, gulp, 80) in order to truly minimize how often you turn it on, can save you a ton of kWh, which could be better used for an EV.
    2. If you have an electric dryer, hanging out some of your clothes to dry can save also save you a lot of kWh for your EV.
    3. Buying a highly efficient fridge and doing the right things (keeping the freezer full, vacuuming the dust from the coils regularly)

    I'm not going to do the specific math on Central AC, electric dryers, and fridges -- but for most people they are primary electric energy hogs in the house.

    It's worth it to save the kWh for an EV. That's because, comparatively speaking, a kWh is much more valuable as a source of fuel for an EV than for a central AC unit -- at least for most of us. 5 to 6 kWh replaces a gallon of gasoline for most of us, or about $3. Compare this to the 50 to 60 cents it would cost me (in Xcel territory in Colorado) to pay for those kWh to run our central AC for about one hour.

    Basically, 50 cents of AC = to $3 worth of gasoline -- and imagine if gasoline prices pushed to $4 or even $5 per gallon!