splitting electric bill - how to calc leaf consumption

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minuit3101

Member
Joined
Jan 19, 2014
Messages
7
Hi! I share a house with a housemate and I'm needing to know how much more of the electric bill I should be covering for my extra utility use. I got the leaf last January. Up until now we have been using the very un-scientific method of comparing this year's bill with the previous year's bill for the same month and I pay the difference. I know that this didn't take into account rising cost of electricity, but oh well. So, now I would like to start paying closer to the amount I'm actually consuming. Is there some kind of formula I can use if I keep track of my miles? (I'm obviously not a math person, so please don't judge!) ;-)
 
Sure. You could log your miles and divide by the miles/kwh number the LEAF tracks. You also need to add a fudge factor for power overhead during the charging cycle. Divide by 0.85 for 240v charging and by 0.75 for 120v charging. Be sure to reset the stats in the car fairly often. I'm sure other folks will be happy to make this more complicated, but the above will be much fairer than what you're doing now.

Better would probably be logging the amount of time the LEAF spends charging and multiplying by the charge rate that your EVSE is supplying to the car. The nice thing about that is you might be able to use the Carwings email notifications to log the start and stop times. These are all approximations, however.

What kind of charging arrangement do you have? Some people have added meters to their circuits to keep track of power consumed. This is very precise, and would be the most fair. Here's two examples of people doing that:

http://www.mynissanleaf.com/viewtopic.php?f=6&t=14989&p=338777&hilit=hialeah#p338777" onclick="window.open(this.href);return false;
http://like2bike.myevblog.com/sample-page/adding-a-kwh-meter-to-an-evse/" onclick="window.open(this.href);return false;
 
Get a proper sub meter. Leviton, EKM Metering, others make them. Done.
 
Just use 0.3 kWh/mi you drive and you will be close enough. Round up to 0.4 kwh/mile if you 120V charge. Close enough for roomate math.
 
Here is a spreadsheet I created to answer a similar question, it might be helpful.
knightmb said:
I've created a spreadsheet with ballpark figures that you can give/print for your room-mate. It used the lowest and highest utility rates since 2013, you need simply line up your utility rate with the percentage of charge to 100% and get a ballpark figure of electricity. It's only meant as a quick cheat sheet, doesn't account for charging losses, heat generation, etc. It is just a good way to get people that don't understand how billing from the electric utility works; a quick glance of how much it *may* cost to charge your leaf from say 0% dead or 50% depleted, etc. You can always round up for half-cent cost to get a little more accuracy (round 9.5 cents to 10 cents for example).

If your room mate can accept this, things can be better in the household. Others are welcome to use/print/distribute as well if they see fit.

Link to PDF Here:
http://nissanleaf.guru/forum/viewtopic.php?f=8&t=12
 
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