cost difference in home outlet and charging station

[divinefavor]

i am a new i3 owner. i charged my i3 using regular home outlet throughout the day to reach full charge for 2 consecutive days now. i can see from my pge (california) account, that usage skyrocketed. i'm afraid my bill may come out to be like $300 if i charge this way. i'd like to know cost comparisons for the following

- using home outlet everyday to fully charge (no charging at the charging station)
- using home charging station for faster charge
- using tier-ed plan from PGE

please share your insights..

 

[alohart]

Any public charging station (EVSE) that is not cost-free will almost certainly cost more than charging at home. If you have time-of-use electricity rates, charging during the high rate period would reduce or possibly eliminate that cost difference, so charging at home during the low rate period would be the most cost-effective.

A Level 2 EVSE (>200 V.) will be slightly more efficient than a Level 1 EVSE (<200 V.).

If you have a tiered plan and charging at home raises you to a higher tier, the cost advantage of charging at home vs. at a public EVSE would be reduced or eliminated, so you need to study your pre-EV usage to determine whether a tiered plan would be advantageous.

But in almost any scenario, charging at home would almost certainly be less costly than buying gasoline for your transportation.

 

[divinefavor]

thanks for info. i just did some reading on PGE website, and i'm not sure if time-of-use plan will save money for my case. i could try to charge during non-peak hours only, but if i continue the usage during peak time, cost may balance out and end up with same result as my current plan. if i take advantage of time-of-use plan, i should be able to save about $50 per month (in theory). but i've had bad experience of using similar plan from PGE ( not for EV though), so it's hard to decide. i guess the best way would be to charge at the free charging station, but that would be quite inconvinient to do as daily routine.

Any public charging station (EVSE) that is not cost-free will almost certainly cost more than charging at home. If you have time-of-use electricity rates, charging during the high rate period would reduce or possibly eliminate that cost difference, so charging at home during the low rate period would be the most cost-effective.

A Level 2 EVSE (>200 V.) will be slightly more efficient than a Level 1 EVSE (<200 V.).

If you have a tiered plan and charging at home raises you to a higher tier, the cost advantage of charging at home vs. at a public EVSE would be reduced or eliminated, so you need to study your pre-EV usage to determine whether a tiered plan would be advantageous.

But in almost any scenario, charging at home would almost certainly be less costly than buying gasoline for your transportation.

 

[Jeffj]

The big variable is how much you are going to drive. If you only drive 15-20 miles a day, then you are never doing a full charge, just the portion of the battery charge that you've used.

The battery capacity of the i3 is 18.8 kWh. Since there is some charging overhead, you can probably assume 20kWh to charge the car from dead empty. Multiply that by your rates to get what it costs per day to charge the car (again assuming dead empty). This would be the maximum increase that you should see.

For most people, however, they rarely use a full charge in a day, so the actual charging is far less than the maximum. You can guesstimate how much you are going to charge the car by looking at the gauge on the control display. Rounding to 20 kWh for a full charge, that implies each bar is ~5 kWh of charge. If you get home and you have 2.5 bars left, then you'll only be charging around 7.5 kWh, substantially less than the maximum.

The other consideration on low-cost charging is that if you only have a level 1 charger, you might not be able to get a full charge during the low cost window (if you are less than 50% charge, it'll take > 10 hours at level 1 to charge, likely longer than the low-cost window). A level 2 charger, though it will cost you to purchase and install, will certainly be able to charge within the low cost window.

One last point (if you exceed the low-cost window) - the charging is not linear. The last 25% that is added to the charge goes in much more slowly than the first 75%. So even if you exceed the low cost window, your charging rate is pretty low and the bulk of the charging probably happened in the low cost window. Once the car is charged, it draws negligible current, so you aren't paying even though it might still be plugged in.

$300 seems awfully high to me for charging at home. Assuming $0.20/kWh (significantly higher than the national average of 12 cents), that translates to 1500 kWh, or 75 full charges from empty. A level 1 charger takes ~20 hours to charge from empty, so you could only do 37 full charges in a month on a level 1. I would guess that the average usage in a month is closer to 200 or 300 kWh, not 1500 kWh. Put another way, 1500 kWh into the i3 would imply nearly 6000 miles of driving per month.

 

[jadnashuanh]

If you use the departure time or setup preconditioning, that could easily consume a few Kw's of energy each time, and depending on when you leave, may often be outside of the low-cost window as well. When all is working right, it will try to charge entirely during the low-cost window, but instead of drawing all the power from the batteries to precondition, it turns on the EVSE again when that needs to start.

 

[divinefavor]

thanks for good info.

i have another question. is there a way for me to set up i3 so that it will stop charging once battery reaches about 75%?? this way i may avoid last 25% of slow charging. i haven't (unfortunately) used i remote app yet, but i guess it should let me check the charging status and remotely disconnect?

i still haven't been able to access i remote app on my phone (posted a diff thread)

 

[jadnashuanh]

As far as I can tell, the only way to stop charging is to have a smart EVSE or, some smart switch connected to it, or unplug your i3. The logic will allow you to delay starting the charge so it can do it in a low-cost window, but once it starts, for the most part, it keeps going until full. Note, once the car does fully charge, it turns off the EVSE, or at least as much as they can be turned off (most of them do not have much of a standby power use - those with a Wi-Fi connection or other smarts probably do use more than the typical one).

 

[divinefavor]

i asked around for those with BEVs and have signed up for time-of-use electricity plan. my conclusion is that it doesn't save you much by switching to this plan. i think you save about $20-$30 (in reality) per month but you also have to be cautious about using electricity during prime time.

good news for me is that i found a free charging station nearby in a mall which i regularly visit at least 3 times a week. hopefully this will save me some money.

btw, is there anyway to stop the active charging using i3 remote app? i didn't see any way to do this.

 

[jadnashuanh]

A few EVSE's out there have remote control (often WiFi) where you can check status at that point and on some, can start or stop charging. Otherwise, the i3 will stop charging only when full, there's a fault detected, or you remove the cable.

 

[NormanF]

Just out of curiosity, if you think your electric bill will be more than $300, what would your bill have been without charging the car?

I remember reading a post somewhere about a woman who moved to California and owned a plug in hybrid. She said that because of low gas prices and high California electric rates she was not going to charge her car until gas prices went back up. I'll see if I can find that article.

 

[jadnashuanh]

FWIW, New England has some of the highest electric rates in the USA, by the time you figure in the fixed costs, distribution, and actual energy, I'm paying about $0.21/kw. Some living elsewhere might find that cheap, but in the USA, that's fairly high. Compared to my ICE, even with the current fuel costs, driving my BEV for energy is about 25% of the cost of driving my ICE, and in the BEV, no oil changes, oil filters, spark plugs, muffler, etc. to degrade each mile of travel and add to the operating costs.