<VV> Electric costs for electric cars?

Frank DuVal corvairduval at cox.net
Wed Nov 30 07:40:55 EST 2011


Charlie:

My electrical rates here in central VA were $0.116 in August (summer 
rates) and $0.101 in October (winter rates). Another reason not to live 
in Southern CA. Well, make that one reason. I used to say earthquakes, 
but then we got damage in the August one here.....

JR,

Your math is right. I was just showing what maximum watts a charger 
could draw from a receptacle. Due to efficiency of the charger these 
days, there is probably no difference in operating cost between 120 or 
240 volt chargers. The 240 would be quicker, as more watts are possible, 
so cost per hour goes up, but time goes down. Should balance out. In 
theory, the chargers are smart and will only run to replenish the lost 
charge in the battery pack, so actual used kwh should be the same for 
both chargers.

This math was more to dispel rumors that charging at home could cost 
$5.00 a day.

Wait, with Charlie's $0.33 per khw, it is possible for the 240 volt 
charger to use $1.27 an hour x  3 hours is $3.81. This took into the mix 
the 80% of 4800 watts maximum pull from the 240v 20a receptacle. This is 
3 times what it would cost me....

Then if everyone in Southern CA came home to plug their car in at the 
same time everyday, the power company fear is they need more 
infrastructure for that load. Hence delayed /timed charging and smart 
meters on the horizon.

You were right to run 240 to the garage, as you can get more watts for 
more heat then a 120 volt circuit with the same amps. The cost, 120 vs 
240 for the same watt heater, would be the same with electric resistance 
heat, as there is no reactance part of the math. Electric motors have 
different calculations.

Frank DuVal

On 11/30/2011 1:27 AM, J R Read wrote:
> Hey Frank,
>
> I forgot all that electric stuff long ago, but I did not forget that 
> 1800 watts/4800 watts = .375
>
> I also know that 8 hours X .375 = 3 hours.  Please let me know if I 
> missed something on that calc.
>
> I don't know about the rest of the calcs that were in there, but it 
> seems to me that if 8 hours for 110/120 volts is correct then 3 hours 
> for 220/240 volts would also be correct.  Using (your) .48/hr cost for 
> the "overnight" charge on 220, the total would be less than a buck and 
> a half for as well. 3 X .48 = $1.44
>
> Did I forget to take another factor into consideration?  I'm not 
> trying to be a smart axx, I'm trying to understand why it would not be 
> cheaper (at least quicker) to use 220 VS 110 to charge up.  The 220 
> would also give room for extra charge time - if needed.
>
> Really, I'm still trying to justify (convince myself that I was right) 
> about the cost of running 220 to my detached garage in order to heat 
> it (when I'm in it) during winter months.
>
> Later, JR
>


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