[hl0m4n]

how would one calculate how much it costs to charge i3 from empty to full based on electricity prices found here: http://www.eia.gov/electricity/month...m?t=epmt_5_6_a

for example ny is 20.88 cents per kilowatthour, do i just multiply by hours needed to charge?

[jadnashuanh]

Under normal circumstances, you can only use about 18.4KwHr of energy from the 22KwHr battery...so assuming it was totally empty (the controller won't let you actually use all of it, nor will it let you charge it all the way up - only 18.4KwHr or so is what you can use)...you'd multiply 18.4Kw x your electrical costs. Note, the conversion isn't perfect...some of the energy will be lost to heat in converting the ACV to DCV to charge the car, so maybe throw in an extra 10%, or say 20KwHr * $0.2088 = $4.18 based on using a 240vac EVSE. It would probably be a bit less, as the conversion is better than that (I think, anyways). Note, if you use the 120vac EVSE that comes with the car, it will take more time and more money to recharge since the conversion to the 400VDC or so it must make to charge the batteries isn't as efficient.

[Kevin_Genius@BMWMtLaurel]

In NJ, it's usually around $3.50-$4.50 to fully charge the i3

[ultraturtle]

According to the EPA, it takes approximately 22 kWh to fully charge the i3's 18.8 kWh useable capacity (internal charger is ~ 85% efficient), so your cost would be ~$4.59 (assuming $0.2088/kWh).

[jadnashuanh]

I think that the EPA used the supplied 120vac EVSE for its measurements...a 240vac one will be more efficient.

[Boatguy]

The amount of power to refill the battery is well established at about 18kWh so with a charge efficiency factor of 80% you would need to buy 22.5kWh. The rate depends on where you live and your rate structure. The optimal rate in northern California (PG&E) is a little less than $0.10 / kWh when charging 11pm - 7am. So that would be $2.20 for a full charge.

Obviously the EPA is using a much higher rate for electricity. Using the optimal PG&E rates and $4/gal of gas would produce an MPGe of around 142. Amazing how far we've come from the Detroit gas guzzlers that got 12mpg and I'm sure all the EV manufacturers think they can do better!

[chrisny]

Ok so if I use a commute I used to have as an example:

70 miles each way to work, chargers at the office (no idea if they were free or not, but lets assume not), I would charge twice a day, once at work, once when I get home. So call that $9 per day and I went in 4 days a week, so $36 a week and let's assume one more charge for weekend driving, call it 40 bucks. I used to spend around $80 - 100 a week on gas when doing that trip in my 335 (@ about 30 mpg, gas around $4/gallon). Not as big of a savings as I was expecting (obviously based only on some rough numbers here, and this is the first I've thought even this much about it…), but still very good and that's with a long commute. Driving around town instead of highway (more the intention of the i3), I would probably get more like 20 mpg in my 335, maybe 22 or 23 tops.

Sound about right?

As a side note, the GW bridge toll each day cost me more than the electric for the i3 would have

[jadnashuanh]

Many, by no means all, ChargePoint EVSEs are free to use (along with some others as well, but some do require registration first - you get a free ChargePoint account with the i3 from BMW), so you may not need to pay for that at work. ANd, if you're lucky, there may be one or more near where you live or shop, and you can top off there. Ideal would be maybe near or at a health club if you use one of those.

I'm averaging about 4.3 miles/kW of use on mine. That's out of the battery..it takes a bit more when trying to replace it (maybe about 10-15%) in losses, battery conditioning, heat.