electric bill

[minuit3101]

Aloha! I'm hoping that someone can help me figure this out. This is my first month with the Leaf. I share a house with someone and need to figure out what portion extra of the electric bill I am going to need to pay and the obvious calculations are coming out to be way more than I thought I was going to be spending on charging. (Yes, I know that Hawaii has some of the most expensive electric rates in the country, but even so....)

Here are some numbers from the bill to compare:
2/15/14 - 628kwH - $241 - 21.66 kwH/day - $8.32/day
1/17/14 - 409 kwH - $156 - 13.19kwH/day - $5.05/day
2/15/13 - 459kwH - $179 - 15.83kwH/day - $6.18/day

Here's where I'm confused. It looks like the difference is somewhere between $2-3/day, but there were a handful of days I didn't even charge at all and I was usually only charging between 25-30% at home. I got the leaf on 1/21/14, so it wasn't even a full month on this bill and it looks like I'm going to be paying about $60-70 extra on the bill. Is this right?

Is there any way to know how many kwH it takes to charge per percentage? (i.e. if I were at 70% capacity and then charged to 100%, how many kwH would I have consumed?)

Any help is hugely appreciated!

 

[davidcary]

Hawaii I guess.

A kwh is about 5% SOC. It isn't quite right but pretty close. Figure 20kwh available in the battery. It is more like 21 but that is balanced by charging losses.

Charging losses vary based on charging rates so without knowing how you are charging, it is all a guess anyway.

You could spend upwards of $10 charging a completely empty battery in Hawaii. A big question is are you on a tiered rate or just high cost all the time?

Feb diff is 160 kwh which should represent 600+ miles of driving in Hawaii (just based on relatively slow speeds and mild climate). If you are charging somewhere else mostly, then you would have to be driving almost 2000 miles a month to have that make sense. Possible something else using more electricity in the house.

Note 120V charging is the most inefficient. With your rates, it may pay to get a 240 installed just on efficiency alone.

 

[RegGuheert]

Without any information about how far you drove during that period and your driving efficiency, there is no way to know how much electricity you used.

One possibility to help you out is that Carwings records that information if you accept the disclaimer in the car. If you have done that, you may have detailed daily records of how much electricity your car used from the battery. In that case, you will need to adjust the energy values to reflect how much was used from the wall.

Please let us know if you have that information and we can help you get a fairly accurate estimate of how much of your bill was due to the LEAF.

 

[DNAinaGoodWay]

If you really want to be accurate, get an EVSE with a built in meter, or install a meter just before your EVSE.

 

[Pipcecil]

Here is a very easy calculation that will probably fit just about right:

Go to your leaf on the dash and look at your total average miles per kW (4ish is pretty decent).

Take your miles per month (you can do a trip reset every month) and then divide by your kW per mile to get total kilowatts. I think most level 2 EVSEs are around 85-90% efficient so divide by .85-.9 that should give you your total kW usage pretty darn close.

 

[Graycenphil]

If you are using the cord that came with the car (120 volt) you can buy a Kill-a-watt meter and plug into that. It will tell you exactly how many KW you used. It will even tell you the cost if you program it with your rates.

That said, in the interest of domestic harmony, you may just have to pay whatever extra electricity is being used, or the others on the bill will never be comfortable with you charging your car.

 

[Elephanthead]

You should pay whatever your housemates tell you to pay plus your normal share. A separate meter and electric bill would be ideal if you don't want to get screwed.

 

[Randy]

Order one of these bad boys and a socket to install before your charging station and it will tell you exactly how much energy you're using...

http://www.hialeahmeter.com/siphwame.html" onclick="window.open(this.href);return false;

 

[Stanton]

You didn't specify whether you are using L1 or L2, but I know of 2 options (I've used both):
1) Buy something called a Modlet to monitor/record (and calculate) your energy usage for whatever outlet it's plugged into to (they make 110v and 220v versions): http://themodlet.com/" onclick="window.open(this.href);return false;
2) Use CarWings to calculate cost based on the usage estimate (this was recommended above, but you also have to realize that there may be days where it doesn't work--so not a sure thing)

Considering the electric rates are considerably higher there, it's probably worth investing in a piece of equipment that can measure exactly what you're using.

 

[donald]

Take your miles per month (you can do a trip reset every month) and then divide by your kW per mile

That'll give you 'square miles per monthly kW'. (Presume you meant 'miles driven divided by miles/kWh')

Best bet is to buy yourself an economy monitor and log the energy going into the car, then there's no arguments.

 

[minuit3101]

wow, everyone!!!!! Thank you sooooo much! This was really helpful! I'll take the weekend to digest it all and figure out how to piece all of these great ideas together!
Mahalo!!!!!!

another question: On Maui, there is an initiative with Hitachi where they are providing the level 2 charger with free installation to a certain number of us who volunteer and whose houses qualify. I got approved the other day and so at some point they will be installing the level 2 charger. Does anyone have one of these meters or modlets installed on the level 2 charger?

 

[GerryAZ]

Here is a link to a company that offers a variety of digital kWh meters: http://www.ekmmetering.com" onclick="window.open(this.href);return false;

I have used an EKM-25IDS and also an Omnimeter Pulse v.4 with my 240-volt EVSE. The Omnimeter requires separate current transformers so the total cost is a little higher, but it is capable of data logging when connected to a computer.

If you want to estimate your consumption from the dash display, I have found that my 2011 (with 3.3 kW charger) gets about 3 miles per kWh from the wall (measured with either of the above meters) when the dash display is 4.0 miles per kWh. I used to average 4.0 miles per kWh on the dash, but now it is typically a bit lower due to using higher performance tires. A 2013 or 2014 LEAF with the 6.6 kW charger is probably a bit more efficient when charging at Level 2 than my 2011.

Gerry

 

[donald]

so at some point they will be installing the level 2 charger. Does anyone have one of these meters or modlets installed on the level 2 charger?

When I had mine installed, I asked the installer to leave a loop of the live wire so I could put a current monitor around it.

He was happy to oblige and put in a second 'junction box', just under the 'junction-box proper', that the cabling came through and left a loop within that box. So it was all safe and properly installed from the compliance point of view. I could then open that box, put a current clamp on the loop, and put a nick in the lid, before refitting it, to route out the wire to the current clamp to the wireless sender that came with the power monitor I got for doing that.

I actually bough two of the same unit, so the two readouts could both read the same sensor signal. So I have two gauges on my desk reading instant drawn power, and drawn energy over the last day (which is usually the amount of the current charging session).

 

[Mtown0031]

May I suggest that you go on e-bay and purchase a used watt hour meter and its base. Then have it installed in line with the outlet you use. You can read it before and after charging. That should help a lot in figuring out your part of the bill. Good luck