Calculating electricity expense

[GIBBER]

Yes Donald but regardless of generation source we are still zero emission at point of use. Without having to mention that no serviceman will ever shed blood to secure a oil supply for my LEAF. 100% electric also means 100% domestic energy production. That makes me feel great.

Depends where the electricity comes from.

 

[KJD]

Can someone give me a formula to calculate the electricity costs to charge the batteries? I called my electric company and they gave me this calculation, which if this is correct, I will be spending $150-$200 a month for electricity.
watts x hours charged per day x days per month x rate (my rate is .09 cents for winter and .11 cents for summer)
I contacted Nissan and they told me to use this formula. (I have the 2013 SL with the 6.6kW on board charger)
6.6 x hours per day charged x electricity rate
Based on these two formulas this is what I would pay for electricity.
6.6 x 8 hours on charge x 30 days x .09(winter rate)=$142.56
I am using the 110-volt charger.
With these figures it isn't any more economical than an economy gasoline car. I am reading that people are paying $20-$60 a month to charge so I don't think these formulas are correct. Any help you can give me will be appreciated. Thank you!

There is a problem with your calculations.
The 120 volt charger only draws about 12 amps.
120 volts * 12 amps = 1440 watts = 1.4kw
I really doubt you will charge 8 hours every day but if you did.

1.4 * 8 * 30 * .09 = $30.24

 

[slcleaf]

Can someone give me a formula to calculate the electricity costs to charge the batteries? I called my electric company and they gave me this calculation, which if this is correct, I will be spending $150-$200 a month for electricity.
watts x hours charged per day x days per month x rate (my rate is .09 cents for winter and .11 cents for summer)
I contacted Nissan and they told me to use this formula. (I have the 2013 SL with the 6.6kW on board charger)
6.6 x hours per day charged x electricity rate
Based on these two formulas this is what I would pay for electricity.
6.6 x 8 hours on charge x 30 days x .09(winter rate)=$142.56
I am using the 110-volt charger.
With these figures it isn't any more economical than an economy gasoline car. I am reading that people are paying $20-$60 a month to charge so I don't think these formulas are correct. Any help you can give me will be appreciated. Thank you!

There is a problem with your calculations.
The 120 volt charger only draws about 12 amps.
120 volts * 12 amps = 1440 watts = 1.4kw
I really doubt you will charge 8 hours every day but if you did.

1.4 * 8 * 30 * .09 = $30.24

Thank you! That sounds more like the estimates I have been hearing. My car is only 3 days old so I imagine the batteries have a break in period. The carwings app is saying it will take 14 hours to charge at 30% capacity right now. That can't be right.

Can I use the kw/mile to calculate the cost it takes to drive the vehcile, similar to a miles per gallon reading on gasoline cars? My dashboard is saying average kw/mile is 4.2.

Thanks!

 

[KJD]

There are some calculations floating around this forum that will get you pretty close. You need to add in the losses for the cooling pump and stuff and I do not remember how much that is right now.

Instead of calculating it, why not just measure it and use real numbers. Take a look at what dgpcolorado built at his place. Very well done.

http://www.mynissanleaf.com/viewtopic.php?f=15&t=13581#p309806" onclick="window.open(this.href);return false;

 

[mbender]

[...]
Based on these two formulas this is what I would pay for electricity.

6.6 x 8 hours on charge x 30 days x .09(winter rate)=$142.56

I am using the 110-volt charger.

With these figures it isn't any more economical than an economy gasoline car.
[...]

Just to reiterate and point out why the above formula is wrong, the 6.6 refers to using the 240V 6.6kW EVSE, but that doesn't apply to you because as you say you're using the 110V EVSE. If you were using the 6.6kW EVSE, you'd probably only charge for 1-2 hours a day (not 8 as you used). So,

minimum (1 hour or 20-25 miles per day in winter): 6.6 x 1 hour x 30 days x $0.09 = $17.82
maximum (2 hours or 40-50 miles per day in summer): 6.6 x 2 hours x 30 days x $0.11 = $43.56

Split the difference for a rough and conservative estimate, and I'd call it $30 a month for 33 miles per day. [ Year round, YMMV :-]

ps. I wish my electricity rates were 9 and 11 cents!

 

[ksnogas2112]

@scleaf....those are the same prices I have for electricity in KS...you'll spend $20-$30/month depending on how many miles you drive and how often you use free public charging.

 

[ERG4ALL]

Leasing appealed to us because we then have no worry about obsolescence or battery life. We get about $200 per month savings in gas, oil, filters, etc. over an ICE car (we have rooftop PV). But there is one other factor. If I purchased a comparable ICE car for say $35,000 and kept it for the same amount of time, i.e. 39 months, and traded for a new car, I would be losing easily another $200 per month and probably more. You can extend the lease vs. purchase time period which will lower the lease payment and also lower the trade in value. Thus, for us anyway, the EV LEAF lease is a fantastic deal.

 

[DarkStar]

My car is only 3 days old so I imagine the batteries have a break in period. The carwings app is saying it will take 14 hours to charge at 30% capacity right now. That can't be right.

That's probably fairly close, my guess is that it will take between 10-12 hours charging at Level 1 to get fully charged.

Since you say you are starting at 30% SOC (estimated, could be a bit off), then to go to 100% would take about 18.5 KWh of electricity (inefficiencies kinda throw this around a bit). If you multiply 18.5 KW, by the rate of $0.09 per KWh, then your cost per day is about $1.67 or about $50.78 per month (if you drive the same mileage everyday and don't use public charging).

Since you're Level 1 charging anyhow, I would recommend picking up a Kill-a-Watt meter as it will automatically calculate the expense based on the usage: http://amzn.com/B000RGF29Q

 

[SanDust]

Can someone give me a formula to calculate the electricity costs to charge the batteries?

Using time and watts and rates is overly complicated. Much simpler to use miles. You'll get about 3 miles per kWh. If you drive 1000 miles a month you'll use 333 kWh which will cost you $37 in the summer and $30 in the winter. Should be a bit better because you'll get more miles per kWh in the summer when the rate is higher. If you find you get more miles per kWh then use the larger number. I think this is the way the EPA does it.

So the formula would be: Miles/3 Miles per kWh X Miles driven X $/kWh = $. You can use miles per day or per month or per year, whatever time frame you want to use.

 

[dgpcolorado]

Thank you! That sounds more like the estimates I have been hearing. My car is only 3 days old so I imagine the batteries have a break in period. The carwings app is saying it will take 14 hours to charge at 30% capacity right now. That can't be right.

Can I use the kw/mile to calculate the cost it takes to drive the vehcile, similar to a miles per gallon reading on gasoline cars? My dashboard is saying average kw/mile is 4.2.

Thanks!

There is no "break in period" for the batteries. They do start to lose capacity from the date of manufacture. You may see the battery holding more or less charge depending on temperature; in winter temperatures the battery capacity will be reduced somewhat compared to summer. But, overall, it is heat that kills the battery so cooler is better for longer life.

If your dash mileage of 4.2 reflects your typical trip you can use that to get an idea of your electricity cost. You can reset that meter for each trip; I reset that one monthly and the one on the console (energy screen) daily to get an idea of how I am doing.

Charging at Level 1, 120 Volts, is about 75% efficient [charging at Level 2 is 86% to 90% efficient, depending on the amperage of the EVSE (charge station)]. So:

4.2 miles/kWh x 0.75 = 3.15 miles/kWh "from the wall" or 0.3175 kWh per mile.

If you drove 50 miles per day then that would be about 16 kWh per day or $1.44 at your 9¢/kWh rate. If you drove 30 miles a day that would cost about 86¢ per day. You can adjust the numbers depending on how far you drive and a more accurate dash mileage if you reset it periodically.

Please bear in mind that your mileage will drop in winter and go up in summer (I am assuming that "slc" in your user name is for Salt Lake City, a place with real winters). If you use the heater that will lower the mileage. (Preheating won't lower the displayed dash mileage but it will increase the electricity used from the "wall"; however, preheating doesn't work very well in very cold weather on Level 1, 120 Volt, charging.) Unlike an ICE car there is no "free" waste heat to use to heat the car. But it is still way cheaper than buying gasoline!

 

[planet4ever]

The carwings app is saying it will take 14 hours to charge at 30% capacity right now. That can't be right.

That's probably fairly close, my guess is that it will take between 10-12 hours charging at Level 1 to get fully charged.

10-12 hours sounds quite low to me. Level 1 charging puts just over one kilowatt (actually about 1.1kW) into the battery. 70% of 21kWh would be 14.7kWh. 14.7kWh/1.1kW = 13.4 hours.

Since you say you are starting at 30% SOC (estimated, could be a bit off), then to go to 100% would take about 18.5 KWh of electricity (inefficiencies kinda throw this around a bit).

A bit more than you seem to be assuming. As dgpcolorado said, L1 charging is about 75% efficient. That 14.7kWh to the battery I calculated above would become 19.6kWh at the wall.

Since you're Level 1 charging anyhow, I would recommend picking up a Kill-a-Watt meter as it will automatically calculate the expense based on the usage

Be careful about that. I suggest you look at this thread: is it safe to use Kill A Watt with EVSE ?

Ray

 

[slcleaf]

Thank you for all the helpful information from everyone! I was a bit worried when I found out how long the level 1 charging was taking and I didn't know how to accurately calculate the electricity costs. I am confident now that I know how many kw the batteries take to charge.

What I have determined this week is that the level 1 charging takes way too long to really make it convenient and you want to be able to charge in home at level 2. For example, my daily commute will be 50 miles round trip. When I get home I should have around 25-35% remaining. If I need to drive the vehicle for other errands I will be extremely limited on where I can drive it. And then to make sure I have an almost full charge for the next day's commute I will need to charge it for another 14-17 hours. I don't sleep for 17 hours a night. At this rate I will not be able to keep up with the charge and unless I can get it to a level 2 charging station or limp into the weekend I am going to run out of battery power.

Level 1 is going to give you about 6-8 miles per hour of charge, while level 2 if going to be about 4 times that. The Nissan dealers here have level 2 stations that we can use free of charge anytime. I plugged into their station and in 1 hour and 10 minutes of charging I went from 29 miles remaining to 65 miles remaining. I think level 1 is ok for people that don't have long commutes and can leave the car on the trickle charger all day. Unless you have a way to charge while the car is sitting at your place of employment then level 1 is going to be a a huge inconvenience!

I am interested in what others have found works for them and what their experiences have been. I will probably have an electrician run a 220 line into my garage and purchase either the charging station from EV solutions that Nissan recommends or retrofit my trickle charge cord to handle the 220 volts that EVSE upgrade will do. There is a salesman that works at the Nissan dealership that did the retrofit and he said it works perfect. The EV solutions charging station requires a 40 amp breaker installed which can mean pulling a permit and adding extra installation costs. You don't want to spend all of your savings in gasoline on EVSE purchases. Thanks!

 

[Boourns]

Keep in mind that while the Nissan dealer offers you free charge any time, most dealers block off their lots when they're closed. Not sure where you're located, but here in Texas that means every night after 9 p.m. and all day Sunday.

You are probably right on the border for whether L1 charging will work for you, depending on how long you're at home. I used just L1 charging for the first 6 weeks I had the Leaf. While my commute is only 32-35 miles each way, as long as I plugged in the car right when I got home (5:45 p.m. or so) and left it plugged in until I left at around 8:00, I had enough to get me to 80% with time to spare. You might not sleep 14 hours, but you could be home for 14-15.

That being said, L2 is MUCH more convenient. You are free on weekends to run around and do 30 miles of errands in the morning, charge, then be ready to go out for a matinee movie in the afternoon.

 

[slcleaf]

Keep in mind that while the Nissan dealer offers you free charge any time, most dealers block off their lots when they're closed. Not sure where you're located, but here in Texas that means every night after 9 p.m. and all day Sunday.

You are probably right on the border for whether L1 charging will work for you, depending on how long you're at home. I used just L1 charging for the first 6 weeks I had the Leaf. While my commute is only 32-35 miles each way, as long as I plugged in the car right when I got home (5:45 p.m. or so) and left it plugged in until I left at around 8:00, I had enough to get me to 80% with time to spare. You might not sleep 14 hours, but you could be home for 14-15.

That being said, L2 is MUCH more convenient. You are free on weekends to run around and do 30 miles of errands in the morning, charge, then be ready to go out for a matinee movie in the afternoon.

Luckily the dealer close to my home leaves their lot unlocked 24/7 and they said I can use it anytime. They are building a brand new facility which will open in 2014 and they will have the first DC quick charge station in Utah.

 

[KJD]

Luckily the dealer close to my home leaves their lot unlocked 24/7 and they said I can use it anytime. They are building a brand new facility which will open in 2014 and they will have the first DC quick charge station in Utah.

Dealer name and location please.

 

[slcleaf]

Luckily the dealer close to my home leaves their lot unlocked 24/7 and they said I can use it anytime. They are building a brand new facility which will open in 2014 and they will have the first DC quick charge station in Utah.

Dealer name and location please.

Tim Dahle Nissan
10785 S. Automall Drive in Sandy.

Also the American Bush on 2630 S. 300 W. in South Salt Lake has free public 240 and 110 charging stations open 24/7. :mrgreen:

 

[planet4ever]

Level 1 is going to give you about 6-8 miles per hour of charge, while level 2 if going to be about 4 times that.

Just so we don't leave incorrect information lying around here, L1 will not give you anywhere close to 6-8 miles per hour of charge. How far you can go depends on your driving efficiency, of course, but for most people 4 miles per hour of charge is a good estimate. For L2, reasonable estimates for most people are 12-13 miles at 16A or 22 miles at 27A. To get 27A you need to have a 30A EVSE and a 6kW charger in the car.

L1 is not practical for a 50 mile round trip commute unless you can also reliably charge at work.

Ray