Cost to charge electric battery

Am I doing the calculations right to figure out how much it will cost charge a car?

So looking at my electric bill we pay $1.3 per therm.
1 therm = 29.3 khw
so 1.3 / 29.3 = 0.044, so 4.4 cents
BMW 530e has a 9.2 khw battery
9.2 x 4.4 = 40 cents to charge

Sounds about right?

L2 charger? You’ll lose some power to the charger in any case but a L1 charger will lose more.

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Sounds too cheap. Who is your provider? I have SCE and I’m on the normal plan, which costs me $.19/kWh for tier1, $.24/kWh for tier 2 and $.42/kWh for high usage.

Electric power is not measured in therms. You pay by KWh.

Your natural gas is measured in therms.


You are absolutely right. My post is totally wrong. Oops. Back to the calculator.

I have Dept of Water in Power in LA.

The prices are set and depend on the usage. Pretty much range from 0.17 - 0.22 cents. So then it is $1.56 to 2.02 to fully charge. If I am understand it right then the car says we are getting 13 miles on the battery (we just got it so maybe it needs a little time to figure out our usage). Overall this isn’t much of a saving over gas. (Not that we were expecting a saving but just trying to figure out if it is even worth charging it).

At those rates it isn’t that great.

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Try this math:
I get 15-17 miles per charge on my 330e and ~37 mpg driving without charging. If you choose the right SCE plan, you can charge between 10pm-8am for 13c per kWh in winter and 12 per in summer. Your ~15 miles will cost about $1.10 then. Without charging ever, using a gallon of gas you’ll go about 37 miles at a cost of $3.75 each gallon (at Costco in SoCal)
37/15x$1.10=$2.71 in electric cost for those 37 miles. If you save 3.75-2.71= ~$1 per 37 miles by charging at home and drive 10000 miles a year that’s 10000/37x$1=$270/year.

If you’re only getting 30 mpg on gas alone, figure $2.20 to charge what will cost $3.75 in gas to go 30 miles, then your annual cost savings (charging with the cheap after-hours plan) is about $517/yr

Costco is saving you about $.60 cents per gallon in SoCal. So greater savings if you go to a regular gas station.

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Another important factor is that at some public locations, you can get free charging. So depending on how many free charges you can get, your savings will be maximized.

You make a few basic mistakes in your calc. Firstly, you need a voltmeter and actually measure what you put in your battery. The ev battery size has 2 numbers…one is the overall size and one is the usable size. Your 9.3 battery is actually 8.
As stated before, L2 has about 10% charging loss while L1 is about 15%…so account for these too. LAWDP has rebates for L2 charger install.
You need to check with your electric provider and see what ev plans they have.

For 10k miles/year…the more you drive the better the savings.
At 17c/kWh with 46kWh/100 miles=> $782
At 22c/kWh => $1012
At $4/gal gas…29mpg => $1379
As you can see, this car is pretty bad for an ev…consumption wise.

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Thanks. Very helpful.
Sorry where is the 46kwh from?

Check the link. That is the ev efficiency.

Combined MPG on Electricity:72mpge
.0 gal/100mi of gas + 46 kWh/100mi

Wife’s Clarity PHEV is a bigger car and gets 31kWh/100mi. Of course, it’s 3s slower on 0-60 mph and not a performance car in any way.

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Try putting the Clarity in sport-mode to activate time-travel and Nascar-like performance.

I’m scared…i heard stories…and all made possible by that back skirt.

That’s how the Clarity generates its’ molecular integrity.


Paying 8.4c/kw in NTX on a recent renewal, free night or weekend plans are $$$ in paid times (20c/kw) considering AC is a fact of life Mar-Nov (varies in use but still)

If I sign up for plan in Nov or Feb sometimes I can snag a plan where 1-1000KW is $30 base rate and 15c/kw after

Also calculate how much $$ extra to INSTALL a fast charger in your garage at home for the BMW 530e? Your electric bill will go up - but how much each month assuming you charge up every day?

The ZAP MAP info is for the UK - prices in UK pounds sterling? Real life mileage range on the 530e looks disappointing.