Smart Car of America Forum banner

1 - 20 of 27 Posts

·
Registered
Joined
·
491 Posts
Discussion Starter #1 (Edited)
How much does it cost you a day to drive your ED to your work?
Tier 1 = 1-13 cents
Tier 2 = 2-16 cents
Tier 3 = 3-31 cents
Tier 4 = 4-34 cents
I averaged 0.20 cents per kWh last month.

I drive about 33 miles per day and come back home with 65% of charge left. I spend about 6 kWh a day about $ 1.20 (6kWh x 0.20).
Many times I charge for free :)
So compared with fuel expense of Hydrogen, natural gas, diesel, gasoline, or other fuel, this little car drives for free:D
 

·
Registered
Joined
·
54 Posts
Mine was 10.8¢ per kWhr last month
56.8 mi round trip commute (weekdays only)
I charge at work for free so by the time I leave from work I have a full charge.
28.4 mi return trip from work leaves me with between 50 and 60% SOC.

If I over-estimate a 3hr daily charge at 3.3kWhr rate I have 9.9kWhrs x 10.8¢ per kWhr = $1.07 per day.

With approx. 22 average number of weekdays per month, my monthly energy bill has increased approx. $23.54

:D
 

·
Registered
Joined
·
462 Posts
As soon as I get my smart, I should be paying 5.9-6.9 cents per kwh depending on the season. Yay cheap Ohio electric prices!
 

·
Registered
Joined
·
527 Posts
Ontario overnight rate is $0.075/KWh. Add in the various transmission, debt retirement and other charges and I am just under $0.13/KWh. On top of that, I pay $30 per month to obtain 100% renewable electricity via BullFrog Power for my total monthly electricity usage (not just the car).

That puts me at $0.15/KWh all in for running my car on community wind and small scale run of the river hydro.

I travel 30km/day 6 days per week and average 20 KWh/100km, so that means I am paying $21/month. That compares to $120/month on my old gas car the ED replaced.

My insurance is $30/mo cheaper too.
Making out like a bandit. Keep those savings comin'!!
 

·
Registered
Joined
·
527 Posts
What is the kW/h rate for the slow charge at 12A?
Watts are watts where I live. Doesn't matter how fast you consume them.

I use the 12A charger to charge my ED. Never failed me once.

Comparisons to the EVSE and charger efficiency have been done by electric car owners of Smart, Leaf and others, and it has been generally found that the 220V 16A is a few percent more efficient than charging at 120V 12A. Most of this is due to charging time being reduced, thereby reducing the amount of time the battery is being exercised and producing heat (waste electricity). The difference is so negligible that no owner should buy a higher power EVSE unless they need to charge faster.

Personally, I want the slower charge time, as I can plug in when I get home, and let it work for >10 hours, making full use of the overnight cheaper electricity.
 

·
Registered
Joined
·
116 Posts
Watts are watts where I live. Doesn't matter how fast you consume them.
Well, the Smart's internal charger limits the charge rate to a maximum of 3.3kWh per hour, doesn't it? If I use the slow charger at 12A and 120V how many kWh does the Smart battery get charged with per hour?
 

·
Registered
Joined
·
832 Posts
120V * 12A = 1.44kW/hr
Why is it so hard to use proper units for power and energy?

power: Volts * Amperes = Watts, once you have 1000 of them, divide by 1000 and call them kilo-Watts.

Energy: apply power for a period of time: kW * h = kWh

I cringe when I see kWh used for power and vice versa, but Schorschis kWh per hour is the best yet! Why not just cancel out the hours and say kW?

btw, the maximum charge rate is 240V * 16A = 3.8kW (or 3.8kWh/h if you prefer) The often repeated 3.3 kW must be a misprint that just kept going...
 

·
Registered
Joined
·
54 Posts
I think you're just taking the UoM way too serious... I work with UoM on a daily basis with a degree in mathematics as a tech writer for the aerospace industry. I realize that V*A = W... what we're discussing is W/hr or kWh or kW/hr in relation to charging time. Hence, why I included the /hr UoM with the calculated result.

I don't know about others, but for me when I see 1440W... I naturally see 1.44 kW. The 1440W/1000 = 1.44 kW isn't necessary... as is the correlation of kW to kWh (or kW/hr) as a unit of measure over a period of time. I understand that not everyone on the forum has a mathematical background, but this level of math and understanding should be basic enough for anyone to draw their own conclusions. :wink:
 

·
Registered
Joined
·
23 Posts
LA DWP averages 15 cents per kwh between Tier 1 and Tier 2

I use about 25% per day so it's less than a buck for me in daily commute
 

·
Registered
Joined
·
1,135 Posts
The often repeated 3.3 kW must be a misprint that just kept going...
The 3.3 kW spec is listed in several places on the smart site, and at the parts manufacturer that makes the charging board (and alternatives, like the DC fast charger). The extra you're seeing is likely waste current, being consumed by the EVSE, the cooling system, the monitor, and/or simply heat loss. That's not even mentioning that often the spec on a given charger board has it's own tollerances that are factored to be off by up to 10% to deal with current changes at these levels. (220 ±10% being "acceptable" for most devices).

There are several factors that could throw off a wattage test by 5 to 10% in this case. One or two readings or computations being off a bit isn't enough to start doubting specs. (This is the EV equivalent of the ">8 gallon gas tank".) >:D
 

·
Registered
Joined
·
1,135 Posts
120V * 12A = 1.44kW/hr
Technically, most people have somewhere between 107 and 127. The "official" spec in the US is 117/234 believe it or not, with a ±10% volt tolerance. Some get higher, some lower, based on a number of factors. I generally do the math at 110, since it's a "worst case" for most people.

As for the OP:

The easiest way (IMO) is to figure out your cost per mile. That makes things much simpler and gives you a far better comparison in the end.

My 2008 smart over the past year averaged $3.98/gallon and 37 MPG, making my operating cost about 10.4¢/mile. The 2013 EV averaged about 2.9 miles/kW, and my average cost for a kW was a hair over 10¢, making the operational cost about 3.3¢/mile. Both values miss a good amount of waste in the process (charging waste, idle/heat waste, etc), but most of that washes out in the averages over a year.

Specifically: I used about ~3300 kW (~$345) and traveled 9690 miles in the 2013 EV in it's first year. The 2008 smart consumed $988 (248 gallons) in gas, and traveled 9456 miles (~37MPG) in roughly the same time frame. I track both car in a spreadsheet, and have for the 2008 ICE since day 1 of ownership. So real world results pan out the ~1/3 cost measurements. I've posted a couple graphs of results based on the data here over the years.
 

·
Registered
Joined
·
74 Posts
I am using the stock EVSE running on a dedicated 120v, 20A circuit.

My power provider shows a rate of 4.4 cents/kWh (not Time related) for anything over 500 kWh used--and we are always over 500. However, when looking at my bills, I could not get the math to add up. I called the power company and got a breakdown of all the costs and found there is a FUEL charge of 2.18 cents/kWh, as well, to cover the expense of the fuel needed to create the power. That seems very deceiving to me because the actual cost of a kWh jumps to 6.58 cents/kWh, and why is fuel cost not already in the standard hourly rate? Is it so they can sound better with their charges? Of course, this also does not include taxes and fees.

I have decided to base my usage calculations for my car on 6.6 cents/kWh to more accurate, and for my first week of driving my car 20 miles to and from work (only 4 days), I used just over kWh (per my kill-a-watt meter) making my daily cost just over $.50 a day. Even with lower gas prices now, my ICE car would have still cost me over $2.00 a day. Once gasoline climbs back up, the disparity will be even greater and my smile larger! :)
 

·
Registered
Joined
·
456 Posts
Personally, I want the slower charge time, as I can plug in when I get home, and let it work for >10 hours, making full use of the overnight cheaper electricity.
I agreed with everything you wrote until you got to this. Many L2 EVSE's, including mine, allow the user to delay charging for a specific number of hours. By doing this, ALL of my charging is done off-peak, not just a portion of it.

My local utility currently doesn't offer competitive off-peak rates so this feature doesn't help me get a lower rate, but it does allow me to help the local utility load-level the demand on their power plants.
 

·
Registered
Joined
·
456 Posts
Since we're all venting, I have to weigh in on one of my pet peeves: Electric power in an sinusoidal AC circuit is volts * amps * power factor (PF). The PF is the cosine of the angle between the voltage and current which largely depends on how inductive the load is. Only a pure resistor or a power supply with a very good PFC (power factor corrector) have a PF of 1.

Everybody keeps assuming that the power factor of an EV charger is 1 when that is not necessarily, and probably is not true. I'd love to know what the PF is for the 3.3KW on-board charger in the ED. Has anybody measured it?
 

·
Registered
Joined
·
456 Posts
So, it doesn't cost me anything to charge my ED.
I applaud your decision to install solar, but as an engineer that has worked in the PV solar industry in the past I can assure you that charging your EV is not free. While the incremental cost of charging your EV may be zero, you either paid handsomely up-front for a solar installation or you're leasing the PV equipment. Either way it is costing you something to charge your EV even if that "something" is a reduction in the amount you get back each month from your local utility.

In any case, you are entitled to brag.
 
1 - 20 of 27 Posts
Top