How to calculate electric usage & cost?

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jpa2825

Well-known member
Joined
May 23, 2012
Messages
124
Location
NKy (Greater Cincinnati)
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!
 
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!
 
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.
 
jpa2825 said:
... 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.
 
neal77 said:
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
 
neal77 said:
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:
http://www.mynissanleaf.com/blog.php?u=291&b=92" onclick="window.open(this.href);return false;

Inexpensive and fairly easy as a DIY project if one is comfortable in working with electric lines. My version:
l620outletandmeter0286s.jpg

evseoutletandmeter0288s.jpg
 
neal77 said:
(dash says 4.2 carwings says 5.0)
You possibly have a bug. It should really match. http://www.mynissanleaf.com/viewtopic.php?f=31&t=9237" onclick="window.open(this.href);return false; is one thread that mentions it. But your newer car shouldn't have this bug...
 
grommet said:
neal77 said:
(dash says 4.2 carwings says 5.0)
You possibly have a bug. It should really match. http://www.mynissanleaf.com/viewtopic.php?f=31&t=9237" onclick="window.open(this.href);return false; 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.]
 
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.
 
Boomer23 said:
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.

What efficiency % might one expect from L1? What about EVSE upgrade into a 240V outlet?
 
jpa2825 said:
Boomer23 said:
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.

What efficiency % might one expect from L1? What about EVSE upgrade into a 240V outlet?

73.5% and 85%
 
"actually", i think it better that for

120 volt 12 amp=75%
240 volt 12 amp=85%
240 volt 16 amp=88%

at least that is my observation
 
dgpcolorado said:
grommet said:
neal77 said:
(dash says 4.2 carwings says 5.0)
You possibly have a bug. It should really match. http://www.mynissanleaf.com/viewtopic.php?f=31&t=9237" onclick="window.open(this.href);return false; 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
Sure. But then why would one compare them directly? :roll:
 
Sorry, please keep in mind I have only had the car for 10 days. I did reset the console (carwings?) once so the 5.0 must be since I reset it. I don't know how to reset the dash so that must be since i have been driving the car.

Thanks for the meter idea. Looks like a good idea and not expensive. I'll keep that in mind.

I was reading on evseupgrade today about how 240 is more efficent than 120. Nice to know that it will use less electricty when I upgrade. Just had a guy come over tonight and install the 240 outlet.
I'm in LA, any idea on total time it will take to send the evse in and get it back? If it is only 3 or 4 days I think I can do it on one charge. If not Nissan is not far away.
 
neal77 said:
I was reading on evseupgrade today about how 240 is more efficent than 120. Nice to know that it will use less electricty when I upgrade. Just had a guy come over tonight and install the 240 outlet.
I'm in LA, any idea on total time it will take to send the evse in and get it back? If it is only 3 or 4 days I think I can do it on one charge. If not Nissan is not far away.
There is an FAQ on the evseupgrade.com website (bottom of the first page) that should answer your questions. If the turnaround time is a problem you can do an "Advanced Replacement" in which you pay a deposit and they send you an upgraded unit first. Then you send them your unmodified one and get your deposit back if it is in like new condition. There is a $75 extra charge for this service:
In a situation where the Nissan EVSE is your only charger?! We offer the advanced replacement option. You pay us an additional $75 handling fee and a deposit of $800, we ship out an already upgraded unit to your specs.
($800 Deposit is fully refunded upon receipt of your original EVSE in like-new condition within a week of receipt of new unit. Units returned scuffed, scratched, etc, may incur a housing replacement charge.)
If you can get by for a few days with other charging options you can just do the exchange the usual way but you might want to call first and ask how long it will take. Vacations can happen this time of the year.
 
BrainDonor said:
jpa2825 said:
... 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.

Do you guys have the option of separate EV rates? A new report shows only 6% of utilities offer EV rates and was wondering if anyone is actually taking advantage of them given the added costs or lifestyle shifts required. Some even require the second meter.

Interested to see if people are experiencing significant savings.

The article:
http://www.prnewswire.com/news-relea...163384196.html" onclick="window.open(this.href);return false;
 
My utility offers an EV rate that is 66% off the normal rate. They required a separate meter that cost $77 and was installed at the same time as the circuit for the EVSE. Well worth it in my case.
 
PlugWiz said:
Do you guys have the option of separate EV rates? A new report shows only 6% of utilities offer EV rates and was wondering if anyone is actually taking advantage of them given the added costs or lifestyle shifts required. Some even require the second meter.
I do not. Also, no time of use rates. One rate, 24 hours a day.
 
PlugWiz said:
Do you guys have the option of separate EV rates? A new report shows only 6% of utilities offer EV rates and was wondering if anyone is actually taking advantage of them given the added costs or lifestyle shifts required. Some even require the second meter.

Interested to see if people are experiencing significant savings.

The article:
http://www.prnewswire.com/news-relea...163384196.html" onclick="window.open(this.href);return false;

My utility, SCE in Southern Calif, offers two different EV charging rates, plus Time of Use rates and these can be combined with solar (or wind) net metering. One of the EV rate plans requires a second meter for just the EV charging, but there is no charge for the meter, neither up front nor monthly. The other plan, the one I chose, is ideal for a home with solar. It uses a single meter for the entire house and TOU rates. We charge at night during Super Off Peak at a low per kWh rate and we get credit at much higher rates per kWh for generated power during peak hours. The net result for us is no power cost for the entire household including our EV charging for 11,000 miles per year, though we used close to 3,000 kWh more power than we generated for the last net metering year (disclaimer, we don't use air conditioning or other high draw power uses during peak hours).
 
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