The Role of Electric Cars in a Sustainable Way of Life

The Role of Electric Cars in a
Sustainable Way of Life
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My main interest in electric cars lies in their role in moving us
toward a sustainable way of life. The biggest barrier to this goal is
its perceived cost. Yet my back-of-the-envelope calculations below
indicate that a net-zero energy house and net-zero energy
automobile combination would be much cheaper over 35 years for
a household than our current use of energy. All costs assume
*NO* subsidies.
Specifically, a typical household today will spend over
$140,000 in energy over the next 35 years for house and
cars, whereas a net-zero energy house and car combination would
cost about $100,000 for the same time period. Below are the
calculations, references, and data for such a conclusion.
Here is the list of my estimates for various costs, as well as
references that I use in my calculations. Note that all cost
estimates are in *TODAY'S* dollars as I exclude inflation from the
Estimates for energy cost for a
conventional house-car scenario
My estimate for annual household energy costs: $2350/yr. Average
electrical costs: $1200/yr:
Average household heating costs ($769-$2349):
Estimates for energy cost for a
conventional house-car scenario
My (conservative) estimate for current
MPG: 30.
Ref: current MPG
My (conservative) estimate for the cost of
a gallon of gas in today's dollars: $2.50.
National average cost/gallon as of
10/26/2009 was $2.67.
Ref: National average cost/gallon>
Estimates For Energy Cost …
My estimate for household miles driven
per year: 21,000 (based on usually more
than one car per household).
Ref: 21,000 miles
So, the energy cost for the conventional
house-car scenario over 35 years is:
( $2350 + (21000/30)*$2.5) ) * 35 =
Estimates for net-zero energy
house as of 2009
The European passive house: my estimate is that building
to this standard would increase the cost of a house by an
average of 10%.
They are called passive houses because they do not require
active systems such as ground-source heat pumps or solar
PV arrays. The only active element is forced air ventilation
through heat exchangers.
Note that the "European passive house" is not at all the
same as the term "passive house" that is used in the US: it
is a very specific and advanced technology that reduces
energy costs far more than is achieved by passive or even
most active solar houses in this country.
Estimates for Net-Zero …
Thousands of these houses have been built across Europe.
They look like ordinary houses, apartments, condominiums,
etc. They tend to be more comfortable, much quieter, have
healthier indoor air quality, require less maintenance,
reduce heating/cooling costs by a factor of 5 or 10,
eliminate the need for a central heating/cooling system,
and use 4 times less energy overall.
Here are other estimates for the additional cost of a
European passive house design:
Ref: 5-7% in Germany
Ref: 4-5%
Ref: up to 14%
And here is reference to the savings in energy use: Ref:
75% less energy
Estimates for Net-Zero …
Comparison of Standard House w/
Passive House
Heat Exchanger for Passive House
75% Reduction in Energy Use
Estimate for Net-Zero …
My estimate for the cost of an average house in the US as of
2009: $240,000. This is a high estimate based on combining 3
regional estimates for Western, Eastern, and Southern houses in
the US.
Ref: House costs
My estimate for the cost of a home energy monitor: $500.
Ref: $200 - $600
My estimate for the cost of solar hot water heating: $10,000.
Ref: 4000 Euro/$5600
Ref: $10,000 - $18,000
Ref: $9000 - $15,100 for *cold* Northern states as per "Solar
Today", June 2009, page 40. Solar heaters in "average" locations
in the US should be cheaper than in Northern states.
Estimate for Net-Zero …
My estimate for *current* PV solar cost is $8/watt.
Ref: $7.6-$8.10
My (conservative) estimate for PV degradation is
Ref: appears to be less at 0.75%/yr
My (conservative) estimate is that in an average location in
the US, over a 35 year lifetime, a 1 KW PV array will
generate an average of 1100 KWH/yr. This is based on the
average 1st year output of 1300 KWH/yr for a 1 KW PV
array, degrading over 35 years at 1%/yr to 900 KWH/yr:
(1300 + 900)/2 = 1100 KWH/YR.
Ref: PV watts per state
Estimate for Net-Zero …
Currently, the average house in the US consumes about 11,000
KWH/year of electricity.
Ref: 936 KWH/mo
and a similar dollar amount in natural gas or oil heat.
By combining the efficiency of a European passive house plus an
energy monitor plus solar hot water heating we should reduce the
TOTAL amount of energy needed by the house to 5000
So a 5 KW solar PV array, which produces an average of 5500
KWH/year for 35 years will convert this house into a net-zero
energy house. It is still connected to the electrical grid, but it
simply uses the grid as a giant storage battery, sending as much
energy back to the grid as it consumes, running the house electric
meter backwards, and so the average annual energy cost for this
house is $0.00 for the next 35 years.
Estimate for Net-Zero …
So the total cost of this upgrade is as
- European passive house design:
10% of $240,000 =
- Energy monitor:
$ 500
- Solar hot water system: $10,000
- 5 KW PV array at $8/watt: $40,000
Estimates for the energy cost for
electric cars
We will give this family 3 electric cars: one full size full
function 5-6 passenger, high performance electric car, and
two tiny 8x5 foot 900 lbs. electric micro cars limited to 35
The high performance family electric car is superior to a gas
equivalent car in almost every way, except for range and
recharging time, due to the qualities of electric motors and
the architectural design freedom of electric drive trains. If
designed from scratch it should get 4.5 miles/KWH.
Ref: the 2850 lb. EV1 got 5.5 miles/KWH
Ref: the 3000+ lb Chevy Volt gets 40 miles on 55% of its
16 KWH battery, and so gets 4.5 miles/KWH.
Energy … Electric Cars
There are a number of cultural, safety and other reasons why Americans do not like
micro cars, such as the SMART car. However, some of these reasons are due to the
fact that downsizing a gas engine car makes it uglier, noisier, dirtier, less efficient,
and much more cramped.
This is because gas engines are such obnoxious devices that they must be
surrounded by all sorts of other things to make them acceptable, such as mufflers,
catalytic converters, variable speed transmissions, fuel, cooling, and oil distribution
systems, pumps, belts, hoses, filters, etc. And it is these very things that get heavily
compromised when the car is greatly downsized.
But electric motors are always quiet, clean, smooth, and efficient regardless of their
size; and limited performance (say, 35 MPH) lightweight cars can be designed where
the drive train takes up zero space: the battery, charger, and inverter can be a
long, wide, but thin pack that makes up the floor of the vehicle (taking up no space),
and the 4 motors are inside the wheels.
Thus a tiny 8x5 foot car that is 10 inches shorter than a SMART car and 1 inch
narrower may still be able to hold 4 adults. So there is reason to believe that a tiny
electric car may be more acceptable to the American public.
Eneryg … Electric Cars
Each of the two micro cars is assumed to get 12 miles/KWH
(this compares with the Aptera which is almost twice as
heavy and far more powerful and which gets 10
Aptera 2E
If the micro cars drive a combined total of 13,000
miles/year, and the full size car drives 8000 miles/year,
then the theoretical annual KWH/year is (8000/4.5) +
(13,000/12) = 2860 KWH/year.
However, there are various losses of efficiency, such as wall
plug-to-battery and other losses. So we build in another
25% loss in efficiency, to get to 3575 KWH/year.
Energy costs for the net-zero
energy house and car
So a 3.5 KW solar PV array will generate an average
of 3850 KWH per year, and will more than cover all of
the energy costs for all 3 cars for 35 years. This adds
$28,000 to the overall cost of the house. So the total
cost of energy for the net-zero energy house and netzero energy cars is:
- Passive house + 5 KW solar PV:
- 3.5 KW PV solar for the 3 cars:
$ 74,500
$ 28,000
- TOTAL energy costs for 35 years:
Thus we have $102,500 for the net-zero energy
house/car combination versus $143,000 for the
conventional house/car combination.
Current situation versus the near
However, there is a problem right now: the only
real electric car in mass production is the
$109,000 super-high performance Tesla Roadster,
which at 0-60 in 3.9 seconds leaves most
Corvettes, Dodge Vipers, and Ferraries in the
Ref: Tesla Motors
But all that is about to change. In 3 years, by
2012, there should be a sizable number of
electric vehicles available (Nissan, Aptera, TH!NK,
iMiev, Chevy Volt, Tesla White Star).
Ref: Nissan Leaf
Tesla Roadster
Nissan Leaf
Current Situation Versus …
In addition, in 3 years the cost of solar PV will significantly
decline. My (conservative) estimate for PV solar in 2012 is
$5.60/watt. Until 4 or 5 years ago, PV costs were declining until
they hit a plateau determined by the supply of purified silicon (the
supply was set by the electronics industry, not PV). But that has
changed and the supply is growing so that the cost of purified
silicon is dropping by a factor of ten. This, as well as many other
reasons, is why the cost of PV will plunge. My estimate assumes a
reduction of 30% by 2012, but others predict a steeper decline.
Ref: $1/watt cell ~ $4/watt for PV
The current cost of the 8.5 (5 + 3.5) KW solar array for the house
and cars is 8500*8 = $68,000. But in three years this should drop
by (5.6/8) *$68,000 = $47,600. So then the total energy cost of
the net-zero energy house and car combination should be $24,000
+ $500 + $10,000 + $47,600 = $82,100, compared with
$143,000 for the conventional house/car combination.
Current Situation Versus …
Note: all of these calculations are for an average house in an average
location in the US. However, there is about a 35% variation, plus or minus,
in solar intensity in the contiguous states. For example, in Tucson, a 1 KW
PV array produces 1663 KWH/year, whereas in Seattle (where I live) it
produces 970 KWH/year.
So, looking at the cost of solar PV, the PV cost of $47,600 should be
modified by +/- %35. So in Tucson, the 8.5 KW PV should cost about
$31,000, whereas in Seattle, it would cost about 64,300. This would yield
total costs as follows:
- Tucson: $24,000 + %500 + $10,000 + $31,000 =
- Seattle: $24,000 + %500 + $10,000 + $64,300 =
So even in Seattle, the cost is much less than for a conventional house.
The Energy Efficiency of Electric
There is a myth that Electric cars (EVs)merely shift the emissions from the car to the
power plant. This is based on the following data:
If an electric car gets ALL of its energy from a coal power plant (the dirtiest kind), it
only reduces the total emissions by 30% compared with regular gasoline cars. So an
EV would produce about 70% of the emissions of a gas engine car.
But a hybrid car reduces emissions by 40%, and so a pure electric car produces
somewhat more emissions than a hybrid car
However, this assumes that we get ALL of our electricity from coal. In fact, as the
chart below shows, we only get about half of our electricity from coal. Of the
remaining 50%, 20% comes from natural gas, which produces only 1/2 the
emissions of coal, and 27% of the remaining 30% (nuclear, hydro, wind, solar,
geothermal, ...) produce almost 0 emissions.
So, if EVs produce 70% of the emissions as gas engine cars when they get their
electricity from coal, and the current electrical grid produces only 60-70% of the
emissions from coal, EVs would produce only (0.6 * 0.7 = 42%) to (0.7 * 0.7 =
49%) of the emissions of gas engine cars which makes them cleaning even then
The Energy Efficiency …
The Energy Efficiency …
So EVs would produce ½ the emissions and would be twice as
energy efficient as gas engine cars. However, there is much more
to the story than that. As was demonstrated above, getting the
electricity from your rooftop PV array makes very good economic
sense and exceptionally good environmental sense. Consider this
Your EV gets 4.5 miles/KWH, which is reduced to 3.6 miles/KWH
when all inefficiencies are counted in
You drive 12000 miles/year, and so you use 3333 KWH/year
A 3.1 KW PV array will generate in excess of 3400 KWH/year, and
at $8/watt, will cost $24,800. Add, say, $2200 for maintenance
over 35 years (mainly the inverter) and your cost is $27,000.
The Energy Efficiency …
At $2.50/gallon, and at 30 MPG, your gasoline cost will be
$35,000 over 35 years. So the EV is 22% less expensive to
But PV arrays produce at least 10 times as much electricity
as is required to build them. So, not only does running
your car off of your own PV array make sense, but it
reduces the overall emissions by a factor of 20 compared
with a gasoline engine car.
In fact some PV arrays, based on thin film cells which are
now becoming competitive with silicon PV cells, produce
nearly 30 times as much energy as required to build them,
thus reducing overall energy and emissions by a factor of
50 to 60.
The Energy Efficiency …
The Energy Efficiency …
So now we are talking about really huge differences between EV and gasoline engine
cars. But the difference does not even stop there. A factor that is seldom considered
is the energy needed to extract, refine, and distribute oil/gas to the transportation
sector. For example, in California, 4.5% of all the electricity and 9% of all the natural
gas is used just for the extraction and refining of oil. This was based on the URL:
which appears to be no longer valid.
A study by Nissan indicates that it takes 7.5 KWH to refine one gallon of gasoline. At
3.6 miles/KWH, that will take an EV 27 miles, about the same distance that a gallon
will drive a gas engine car. So in fact, we see that gas cars use as much
electricity/mile as EVs, but in addition consume huge amounts of gasoline. It may
turn out that if we were all driving EVs, we would actually reduce the amount of
electricity we use, as well as radically reducing the use of fossil fuels.
This probably does not even include the amounts of energy needed for the
exploration, transport, and distribution of oil and its products.
So EVs are enormously more efficient that gas engine cars, not to mention the huge
savings in materials and energy needed for maintenance.
The Energy Efficiency …
So EVs are enormously more efficient that gas engine cars, not to mention the huge savings in
materials and energy needed for maintenance.
But we are not done yet: within the next 10 years we will likely see V2G: vehicle to grid technology
in place. Ref:
By far the weakest part of our energy system is energy storage, which has always been too
expensive. But if we use the batteries in EVs, for grid storage, the batteries are already paid for.
Making use of this storage would not be a problem for an EV owner. Lets assume that their battery
gives them a range of, say, 150 miles on a charge. Since the average trip per day is less than 40
miles, the EV owner could use a “smart” phone to tell the car to allow for, say, 50 miles of energy
to be sent to the grid. If they need a longer range, they could turn off the energy sharing feature
for a day.
It is estimated that if we were all driving EVs, the energy stored in the car’s batteries would equal 5
times the total electrical generating capacity of the USA, and that it could earn each EV user up tp
$4000 per year by selling electricity to the grid. Ref:
Better Ways to Finance
However, there are two problems with costs that
we have not considered:
The costs are all up front. The net-zero energy
house/car combination may cost $40,000 less
than a conventional house/car combination, but
the $100,000 cost is all up front.
And we have not included the costs of the electric
car itself, which may be very high due to the high
cost of batteries.
Better Ways to Finance
To answer the first problem, several companies have
created a different financing model for the most expensive
part of the net-zero energy system: the solar PV arrays.
They install the PV arrays for a small up front fee, say
$1000, and then charge you for the electricity that you use.
SolarCity, a California firm is one such example. They will
install a PV array for $1000 to $3000, depending on the
size of the array, and then charge you for the electricity
they make. Customers who use a substantial amount of
electricity will save money compared with their current
electric bills. But since the net-zero energy houses
descibed in previous slides will dramatically cut all energy
costs, this financing should lower the cost for all users.
Better Ways to Finance
To handle the 2nd problem, some EV firms plan to sell you the car, but only
lease the batteries.
The reason for this, is that an EV is extremely simple, and ultimately
should be much less expensive to produce than a gas engine car, but the
batteries are very expensive.
However, the batteries have the potential for a long life as energy storage
devices after they are used in a car. So by selling you the car, but leasing
the batteries, the firm can reclaim the batteries after they no longer
provide sufficient power for the car, but can serve for decades as energy
storage devices.
He Nissan Leaf is one such example: the car will sell for only 1-2% more
than a gas engine car with comparable performance, safety, convenience,
and passenger/cargo size, but you will be charged a monthly battery fee
based on the number of miles you drive. That fee, however, should be
less than the operating cost of a gas engine car.
Other Advantages
So we see that the net-zero energy house/car combination
actually costs less than conventional house/car combinations. But
that is only one of the advantages. Here is the list of advantages:
Much lower cost over 35 years
Fixed energy costs as opposed to highly volatile costs
Energy security: even if the grid goes down for extended periods
of time, you will always have enough energy for vital services
Much lower maintenance cost for both house and cars
Quieter and more comfortable house and cars.
-- Larry
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