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Please help me figure out my charging costs

tes-s

Active Member
Oct 6, 2013
2,947
3,991
CT
Yes, that makes sense. Thanks!

Yea, good rate. We have hydro electric running year round. The rate is one of the reasons that got me to take the plunge!
If you want to fine-tune the "4" for your driving habits, or for a Y, S, or X:

Look at your wh/mi in the car. Multiply by 1.15 to add charging overhead, and account for overnight losses. Divide it into 1000 to get your factor. If you do a lot of sentry mode and preheat the car a lot, multiply by 1.2 to account for that.

"Factor" = 1000 / (wh/mi * 1.15)

The "factor" is your miles per kWh. It will never be perfect, but should give you a good idea of your home charging costs.
 
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Your math not mine but I have no idea. Not said to impress our home is over 4,000 sq.ft. and we use a lot of electricity. 3 or 4 bucks a day this time a year is fine by me.
Was just curious. I used your original screen shots for the calculation. It is rounding the amounts and kWh in it so just assumed close to $0.15 (may be $0.145) per kWh.

$6 / 39 kWh = $0.153 per kWh
$9 / 63 kWh = $0.142 per kWh

We're on Cobb EMC in Woodstock and it is a flat rate of 8.5¢ per kWh. I know GA Power charges different rates for different locations though. Wasn't sure how much though.

I saw you mention the timed/tiered rates driving up costs when switching to them. My quick calculations would support that after checking Cobb EMC tiered offering. The heat load during the summer, here in the south, and an increase to 13.5¢per kWh from 1:00 PM to 9:00 PM would likely drive the cost up even though they offer free 400 kWh per month from midnight to 6:00 AM. The free vehicle charging certainly wouldn't offset the increased AC bill (and we like keeping it cold, 72 at most and likely 70 if I am home) for about 4500 sq/ft.
 
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SaintMickey®

Closed
Sep 19, 2021
117
56
USA
Was just curious. I used your original screen shots for the calculation. It is rounding the amounts and kWh in it so just assumed close to $0.15 (may be $0.145) per kWh.

$6 / 39 kWh = $0.153 per kWh
$9 / 63 kWh = $0.142 per kWh

We're on Cobb EMC in Woodstock and it is a flat rate of 8.5¢ per kWh. I know GA Power charges different rates for different locations though. Wasn't sure how much though.

I saw you mention the timed/tiered rates driving up costs when switching to them. My quick calculations would support that after checking Cobb EMC tiered offering. The heat load during the summer, here in the south, and an increase to 13.5¢per kWh from 1:00 PM to 9:00 PM would likely drive the cost up even though they offer free 400 kWh per month from midnight to 6:00 AM. The free vehicle charging certainly wouldn't offset the increased AC bill (and we like keeping it cold, 72 at most and likely 70 if I am home) for about 4500 sq/ft.

You got a bigger brain than me brother! I'm over in Gwinnett County.

Thanks for the info.
 
OP is like a CEO, quarterly bottomline is the only thing that matters. There is nothing wrong with this approach, but not accounting for all the variables give a really false sense of savings (or lack thereof). As many pointed out, OP's monthly increase is not solely for the new Tesla but probably includes other increase in usages such as air conditioning. Looking back at the last few months, I can see I have turned AC on for the house at least 10+ times. That easily translates to 300-400 kWh extra usage.

If I was to believe TeslaMate (self hosted TeslaFi), it took me 104kWh of electricity for the last 302 miles of driving. This assumes all inefficiency, vampire drains, air conditioning, sentry mode, whatever. I am constantly amazed at how often the car is "awake" with some sort of pump running. All those takes energy but contributes nothing to the actual driving. If you use the figure above, I am only getting about 3 miles to each kWh pumped in. This is roughly $0.03 to $0.04 per mile for SDG&E EV-TOU5 rate (not including the monthly $16 charge for the privilege of the $0.09 super off-peak rate). At the end of the day, this is still cheaper than the per mile cost of a Toyota Prius (which roughly doubles/triples to $0.09 / mile @ $4.30/gallon gas for 50MPG).

If OP has to charge the car with higher cost electricity, there may not be any savings. Once again, depending on the SDG&E tariff choice, it can cost as high as $0.56 / kWh for TOU during summer and even without TOU, 900kWh usage may put the cost in the $0.40 range. This is on-par with Super Charger's rate at $0.41 in most San Diego. There is NO SAVINGS if OP keeps pumping in expensive electricity. This is the joy of living in SoCal.

As many has already pointed out, OP needs to dig in just a little bit into the monthly SDG&E statement and see which tariff they have and potentially figure a way to get cheaper electricity consistently. TOU only make sense if you can avoid usage at 4pm to 9pm ($0.56/kWh). Imaging running your AC during those time!
 
Last edited:

jjgg

Member
May 21, 2021
263
323
Vancouver
OP is like a CEO, quarterly bottomline is the only thing that matters. There is nothing wrong with this approach, but not accounting for all the variables give a really false sense of savings (or lack thereof). As many pointed out, OP's monthly increase is not solely for the new Tesla but probably includes other increase in usages such as air conditioning. Looking back at the last few months, I can see I have turned AC on for the house at least 10+ times. That easily translates to 300-400 kWh extra usage.

If I was to believe TeslaMate (self hosted TeslaFi), it took me 104kWh of electricity for the last 302 miles of driving. This assumes all inefficiency, vampire drains, air conditioning, sentry mode, whatever. I am constantly amazed at how often the car is "awake" with some sort of pump running. All those takes energy but contributes nothing to the actual driving. If you use the figure above, I am only getting about 3 miles to each kWh pumped in. This is roughly $0.03 to $0.04 per mile for SDG&E EV-TOU5 rate (not including the monthly $16 charge for the privilege of the $0.09 super off-peak rate). At the end of the day, this is still cheaper than the per mile cost of a Toyota Prius (which roughly doubles/triples to $0.09 / mile @ $4.30/gallon gas for 50MPG).

If OP has to charge the car with higher cost electricity, there may not be any savings. Once again, depending on the SDG&E tariff choice, it can cost as high as $0.56 / kWh for TOU during summer and even without TOU, 900kWh usage may put the cost in the $0.40 range. This is on-par with Super Charger's rate at $0.41 in most San Diego. There is NO SAVINGS if OP keeps pumping in expensive electricity. This is the joy of living in SoCal.

As many has already pointed out, OP needs to dig in just a little bit into the monthly SDG&E statement and see which tariff they have and potentially figure a way to get cheaper electricity consistently. TOU only make sense if you can avoid usage at 4pm to 9pm ($0.56/kWh). Imaging running your AC during those time!
I think at this point, pretty much all of us have a conclusion that this is not about "charging cost" any more. Maybe a moderator should consider making the title of this thread less misleading, something like "figure out high electricity bill".
 
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Sunny5280

Member
Jul 29, 2021
149
96
Colorado
I think at this point, pretty much all of us have a conclusion that this is not about "charging cost" any more. Maybe a moderator should consider making the title of this thread less misleading, something like "figure out high electricity bill".
The title is what a moderator already made it. See the fourth paragraph in this post of theirs:

 

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