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Posted by Grant Beuchel on July 24, 2003, 3:25 am
Saw an interesting article on steve spences web page about electric cars.  I
was wondering, how many kwh would it take to drive 200 miles?

Now I know there are a multitude of factors that go into this, but I was
just wondering about approximates.

The reason I ask is because I drive 200 miles a day to and from work, and I
was wondering if generating that kind of electricity was at all feasible.

Posted by Anthony Matonak on July 24, 2003, 3:36 am
Grant Beuchel wrote:

The EV1 and various other cars of similar level of technology seem to
run about 3 miles per kwh. Most EV car conversions, where you take a
normal small car and convert it to electric, seem to run about 1 mile
per kwh. 200 miles would require between 67 to 200 kwh.


Posted by JeroenH on July 24, 2003, 8:31 am
You'd be hard pressed to find an affordable E-car that you can drive for 200
miles in real-world conditions (i.e. at highway speeds, and some stop&go on
both ends of the journey). Even the GM EV1, which was supposedly as good an
electric car as possible with current technology, only has an 80 mile range,
and that is while driving very conservatively. Real-world drivers reported
ranges of about 50 miles. Running your batteries completely flat is bad for

The EV1 uses about 26 kWh/100 miles on lead-acid batteries, and about 32
kWh/ 100 miles with a NiMH-pack. Not sure why there is a difference.

Driving 200 miles/day for about 200 days/year would use about 10MWh of
electricity per year. This would require about 13000 square meters of PV to

Would it be better, energy-wise, than burning gasoline? Maybe, but it would
require huge investments which most people can't afford.

Posted by Eric on July 25, 2003, 8:10 pm
that sounds right.

',397wh/day (365 days per year to collect).
 /4 avg sun hours per day = 6,849watts needed.  at 100w/m2, wouldn't
that be 68.5 m2 of PV req'd?

somebody check my math please.

Posted by Anthony Matonak on July 26, 2003, 3:43 am
 Eric wrote:

I would round the numbers to about 3 miles per kWh because it's easier
on my brain than 32 kWh/100 miles. Figuring 50 weeks of work a year,
a couple of weeks off for vacation, and 5 days a week then that seems
to come out to some 250 days/year commuting. 200 Miles a day x 250 days
would then be 50,000 miles a year. At 3 miles per kWh this would come
out to 16,667 kWh/year. I can't remember if the figures from the EV1
were from the outlet or from the battery. To be on the safe side, I
would figure an addition 20% for charging losses. That would come out
to some 20,000 kWh/year.

Now, if we figure a grid tied solar PV system to generate this amount
of energy over the year then it would partly depend on where you are
located. For the majority of the United States you get around 4.5 sun
hours a day on average. 20,0000 kWh/year would come out to about 54.8
kWh/day. At 4.5 sun hours a day this is (54.8 / 4.5) 12.18 kW of PV.
PV panels really only produce about 80% of their STC rating in the real
world and the inverter is usually only 90% efficient. This means that to
generate 12.18 kW you would need (12.18 / .80 / .90) 16.92 kW of PV at
the STC rating (which is how they are sold).

PV panels run about 12% efficient at their STC rating so this would
come out to about 120 watts/m^2. So 16,920 watts would measure some
141 m^2.

I've seen grid tied PV packages (all the parts, none of the labor) being
advertised at around $5,000 for 3,000 watts STC or about 10 kWh/day
into the grid. This is roughly $/watt so an array of 17,000 watts would
cost roughly $5,000. Probably more if you include labor, less if you
have some kind of government hand out. Some places will pay as much as
50% of the cost of your PV system.

Well, let's consider... Gasoline costs about $.70/gallon. An average
car gets around 20 mpg. 50,000 miles a year would require 2,500 gallons
costing around $,250 at current prices. For 20 years of driving, the
same amount of time a PV system could be expected to last, this would
total up to $5,000. Seems like it would cost about the same either way.

The cheapest solution may be simply to move closer to work. Or work
closer to home.


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