jpa2825
Posts: 112
Joined: Wed May 23, 2012 5:16 am
Delivery Date: 25 Aug 2012
Leaf Number: 022029
Location: NKy (Greater Cincinnati)

How to calculate electric usage & cost?

Thu Aug 02, 2012 8:10 am

DISCLAIMER: Considering leasing, so I don't have full access or understanding yet.

A - How do I get "wall to wheels" electric consumption to charge the LEAF? I assume you can use the Avg. kWh/mile reported by LEAF to determine how many kWh have been consumed. E.g., if LEAF is reporting 4.5 kWh/mile since last reset AND I have traveled 100 miles, I could argue I have consumed 45 kWh, right? However, I have read there is efficiency loss such that if I pulled 45 kWh from my utility company, I would not get 45 kWh in my LEAF. What is that inefficiency loss? Assume it is larger at L1 rather than L2 charging.

Alternatively, do L2 chargers tell you how much has been pulled from the utility company?

B - Once I am able to calculate the amount of kWhs I have put into a LEAF, I need to know how much I am paying for those kWhs. In reading my electric bill, I am not sure I understand the full cost. (I realize my electric rates are probably low. I am in KY and we produce and use a lot of coal.)

I can't post the screen capture of my most recent 3 electric bills (if there is a way to do this, please let me know), but here is the data I can gather from it:

APR - Eff. Rate was $.0893/kWh ($99.39 / 1,113kWh used) (incl. $4.60 Customer Charge, rate of $0.077366, 3 "riders" and 1 "adjustment" to achieve the total of $99.39)
MAY - Eff. Rate is $.0863/kWh ($134.98 / 1,564kWh used) (rate for 1 "rider" and the "adjustment" changed)
JUN - Eff. Rate is $.0857/kWh ($151.92 / 1,773kWh used) (rate for "riders" was same as in MAY, but "adjustment" changed)


Help, Help -- I'm being repressed!
2012 Cayenne Red SL
ODO: 46 upon pickup; ~23k in AUG 2014

drees
Moderator
Posts: 5637
Joined: Fri Apr 23, 2010 3:51 pm
Delivery Date: 07 Jun 2011
Leaf Number: 002448
Location: San Diego

Re: How to calculate electric usage & cost?

Thu Aug 02, 2012 10:06 am

To get wall-to-wheels most people have some sort of dedicated meter on the line that feeds their home EVSE. Obviously, this won't track any electricity used when charging away from home. There are a number of solutions from a refurb utility meters (buy a regular meter socket and the meter online - meter is around $35, socket about the same) - EKM Metering also has utility grade meters at a reasonable cost with remote monitoring features.

Failing that - the dash/center console readouts are generally slightly higher than what the wall-to-wheel measurement and dosn't include charging losses. L1 charging is less efficient than L2 charging. L1 is generally around high 70% to low 80% efficient, while L2 charging is mid-high 80% efficient. The center console tends to read 0.1 mi/kWh higher than the dash - they can be reset individually and many people reset one (typically the dash) after each charge to watch efficiency.

To calculate cost to charge, simply take your incremental cost of electrcity (which can be different than your average cost shown on your bill if your plan is not a flat-rate plan) and multiply by your estimated wall-to-wheels efficiency and miles driven. Most people typically get from 3.0-4.0 mi/kWh from the wall. So 100 miles will use between 25-33 kWh.

Looks like your rate is less than $0.09/kWh - say you drive 1,000 miles/month at 3.3 mi/kWh will cost you about $27/month or less than 3c/mile!

Your mileage may vary!
2011 LEAF SL delivered Jun 2011
Stats: Jun 2015: 40k 49.9Ah 214/176 GID - 11th bar lost: 11/11/14 @ 51.56Ah 220/181 GID, 12th lost: 9/23/13 @ 55.25Ah 228/194 GID
3.24 kW Enphase PV System

neal77
Posts: 31
Joined: Mon Mar 19, 2012 10:16 pm
Delivery Date: 21 Jul 2012
Leaf Number: 021484
Location: Norwalk CA

Re: How to calculate electric usage & cost?

Thu Aug 02, 2012 10:30 am

I was wondering the same thing. I am using the cars evse and I am going to upgrade it with Phils evseupgrade. It would be nice to know how many kw I am putting into the car. I am planning on installing an L6-20 socket to plug in the upgraded evse. I understand that I can multiply the dash kw per mile (dash says 4.2 carwings says 5.0) but that only gives you what the car has used, not what you put in it.
2012 Nissan Leaf Blue Ocean
Leased 07/21/2012
100 mile club 09/07/12
11 bars 02/05/14

BrainDonor
Posts: 178
Joined: Sun Aug 28, 2011 7:53 pm
Delivery Date: 30 Nov 2011
Leaf Number: 15727
Location: Lake Worth, FL

Re: How to calculate electric usage & cost?

Thu Aug 02, 2012 10:45 am

jpa2825 wrote:... E.g., if LEAF is reporting 4.5 kWh/mile since last reset AND I have traveled 100 miles, I could argue I have consumed 45 kWh, right? However, I have read there is efficiency loss such that if I pulled 45 kWh from my utility company, I would not get 45 kWh in my LEAF. What is that inefficiency loss? Assume it is larger at L1 rather than L2 charging.


jpa, I think you meant to say 4.5 miles/kWh. In this case, for 100 miles you would use up 100/4.5 = 22.2 kWh of electricity. At a rate of $0.09/kWh, your cost would be exactly $2 to drive 100 miles! For comparison, a Prius would use up about 2 gallons of gasoline to drive 100 miles, which would cost somewhere between $7 and $8 at today's gas prices. So driving electric for you would be at least 3 times cheaper than the most efficient ICE on the market. Note that 4.5 miles/kWh is pretty good "electric mileage".

P.S.: I live in South Florida where our electricity costs $0.11/kWh. We've put over 10,000 miles in 8 months, and I have not seen any increase in my electric bill at all! Some months it's actually cheaper than the same month in the prior year.
2012 SL Glacier Pearl
As of 10/15/2014: [34.5 months][40,020 miles][8 bars]
Reserved: May 25, 2010
Ordered: Aug 30, 2011
Delivered: Nov 30, 2011

BrainDonor
Posts: 178
Joined: Sun Aug 28, 2011 7:53 pm
Delivery Date: 30 Nov 2011
Leaf Number: 15727
Location: Lake Worth, FL

Re: How to calculate electric usage & cost?

Thu Aug 02, 2012 10:48 am

neal77 wrote:I was wondering the same thing. I am using the cars evse and I am going to upgrade it with Phils evseupgrade. It would be nice to know how many kw I am putting into the car. I am planning on installing an L6-20 socket to plug in the upgraded evse. I understand that I can multiply the dash kw per mile (dash says 4.2 carwings says 5.0) but that only gives you what the car has used, not what you put in it.

Neal, you may want to update your delivery date, otherwise you have the oldest LEAF around! :D
2012 SL Glacier Pearl
As of 10/15/2014: [34.5 months][40,020 miles][8 bars]
Reserved: May 25, 2010
Ordered: Aug 30, 2011
Delivered: Nov 30, 2011

neal77
Posts: 31
Joined: Mon Mar 19, 2012 10:16 pm
Delivery Date: 21 Jul 2012
Leaf Number: 021484
Location: Norwalk CA

Re: How to calculate electric usage & cost?

Thu Aug 02, 2012 11:04 am

LOL I just saw that. Thanks. Yes I have been waiting a long time for my Leaf.
2012 Nissan Leaf Blue Ocean
Leased 07/21/2012
100 mile club 09/07/12
11 bars 02/05/14

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dgpcolorado
Forum Supporter
Posts: 2629
Joined: Sat Aug 20, 2011 1:56 pm
Delivery Date: 15 Dec 2011
Leaf Number: 15889
Location: The Western Slope, Colorado

Re: How to calculate electric usage & cost?

Thu Aug 02, 2012 11:12 am

neal77 wrote:I was wondering the same thing. I am using the cars evse and I am going to upgrade it with Phils evseupgrade. It would be nice to know how many kw I am putting into the car. I am planning on installing an L6-20 socket to plug in the upgraded evse. I understand that I can multiply the dash kw per mile (dash says 4.2 carwings says 5.0) but that only gives you what the car has used, not what you put in it.
I installed a refurb utility meter like the one DaveinOlyWA describes here:
blog.php?u=291&b=92

Inexpensive and fairly easy as a DIY project if one is comfortable in working with electric lines. My version:
Image
Image
6-28-15: 27,500 miles, Battery Capacity: 55.93 Ah [from LeafDD] 229 Gids at 100%
Lost first CB 6-3-15, 55.75 Ahr, 26,939 miles
Blue 2012 SV ordered 8-30-11 (Colvin Auto Ctr, McMinnville, OR), Delivered: 12-15-11

grommet
Posts: 349
Joined: Wed Aug 11, 2010 9:57 am
Delivery Date: 03 Jun 2011
Leaf Number: 3612
Location: Silicon Valley

Re: How to calculate electric usage & cost?

Thu Aug 02, 2012 11:21 am

neal77 wrote:(dash says 4.2 carwings says 5.0)
You possibly have a bug. It should really match. viewtopic.php?f=31&t=9237 is one thread that mentions it. But your newer car shouldn't have this bug...

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dgpcolorado
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Posts: 2629
Joined: Sat Aug 20, 2011 1:56 pm
Delivery Date: 15 Dec 2011
Leaf Number: 15889
Location: The Western Slope, Colorado

Re: How to calculate electric usage & cost?

Thu Aug 02, 2012 11:30 am

grommet wrote:
neal77 wrote:(dash says 4.2 carwings says 5.0)
You possibly have a bug. It should really match. viewtopic.php?f=31&t=9237 is one thread that mentions it. But your newer car shouldn't have this bug...
Depends on when each meter was last reset. Yes, a simple-minded possible explanation of the difference, just sayin'... [My meters don't match because I set the dash one monthly and the console one daily.]
6-28-15: 27,500 miles, Battery Capacity: 55.93 Ah [from LeafDD] 229 Gids at 100%
Lost first CB 6-3-15, 55.75 Ahr, 26,939 miles
Blue 2012 SV ordered 8-30-11 (Colvin Auto Ctr, McMinnville, OR), Delivered: 12-15-11

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Boomer23
Posts: 3434
Joined: Sun May 23, 2010 9:57 pm
Delivery Date: 30 Mar 2011
Location: Orange County, CA

Re: How to calculate electric usage & cost?

Thu Aug 02, 2012 11:35 am

For L2 charging, use 85% efficiency as a reasonable estimate.

As an option to the utility meter and socket, you might consider a TED monitoring system. It'll be more expensive than the dedicated utility meter option but it provides data archiving and can help you to understand your other power draws better. TED can be finicky to set up , though.
Black 2013 SL Premium Max Gids 263, 60.34 A
2014 BMW i3 with Range Extender
Blog: http://drivingelectric.blogspot.com

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