The actual price of charging (at home)

[EVer Hopeful]

Dusting off the Grammar School Physics memories here but if

Watts = Volts x Amps

and I have the HPWC on a 240v circuit set to 30A, which for the 80% rule is really a 24A pull, then I'm drawing

240 x 24 ==> 5760 Watts or 5.76 kW

and if I do that for an hour I will have used 5.76 kWh - might as well call that 6 kWh

and looking at my plan, I'm paying somewhere between 8.6 and 9.1 cents per kWh [1] (and 100% renewable ) so call that 9c per kWh


Therefore it costs me 54 cents an hour to charge my vehicle at home


Now all I need to figure out is how far I go on that amount of charge




[1] I change to a new provider every time the plan expires as the "new customer" rates are always better than the ones for existing customers - sort of a reverse loyalty program

 

[Sophias_dad]

Yes, you have the math right.

 

[Rocky_H]

Now all I need to figure out is how far I go on that amount of charge

And here's how to figure that part. I use some of this to give general ballpark numbers to people.

My old Model S is a bit over 300 watt hours per mile most of the time. Let's say 333 to make the math simple. That's one third of a kWh per mile, or 3 miles per each kWh. If you are Super Efficiency Guy (TM) with a Model 3, then maybe you get close to 250 Wh per mile? That would be 4 miles per kWh. So let's say something like 3.5 average to split the difference.

So let's say someone does 15,000 miles per year. Divided by 3.5 miles per kWh, that is 4,285 kWh for the year. Using your 9 cents number, that's about $386 for the entire year of driving.

People may point out that charging is not 100% efficient, so there is some energy that you pay for from the wall that does not make it into the car and is not in the driving Wh per mile numbers. You can hand-wavingly account for that by just assuming a little closer to 3 miles per kWh than 4.

 

[thecavalry]

I have solar at my house, with net metering. I end up with credits every month beyond my normal electric bill. So I’m not overly concerned when I get my EV next month about the expense.

It will be far cheaper than gasoline with or without solar. But even more so since I already put it on the roof.

 

[boulder.dude]

Dedicate Trip B to “Monthly Total,” and use a reminder to every first of the month put the numbers into a spreadsheet and reset. Then multiply the monthly kWh by your rate to figure out monthly cost (and cost per mile).

 

[SwampNut]

I pay 5.5 cents per kWH, so my effective cost per mile is about 1.4 or 1.5 cents.

 

[jcanoe]

When you look at your utility bill make sure you are including any distribution charge per kWh and not just the power generation charge per kWh. Also include any taxes and fees. I divide the total monthly bill by the kWh consumed to arrive at the cost per kWh. Example: $95 for September 2021 divided by 600 kWh equals $0.158 per kWh.

When charging there are conversion and charging losses. Most data shows that 240V charging is between 90% and 95% efficient. The difference is lost as heat energy in the wires, electronics and the battery. To keep it simple, I use 90% for my estimated charging efficiency. This takes into account any required cooling of the battery while charging in the warmer months and any required heating of the battery while charging in the colder months.

The estimated 5760W you are consuming while charging (~5.8kW per hour; 5.8kWh) is netting approximately 5184W (5.2kW per hour; 5.2kWh) added to the battery each hour.

How far you can travel in the Tesla Model Y on 5kWh? That dependent on your energy consumption (Wh/mile) and that is most impacted by your speed. If you view your Trip A or Trip B energy consumption (some rename Trip B to be Lifetime) efficiency in Wh/mile you may see a number between 240Wh/mi and perhaps 350Wh/mi. For reference 250Wh/mile is 4 miles per kWh. Divide 5kWh/.250kWh/mile and you get 20 miles. 5kWh/.300kWh/mile = 16.7 miles. 5kWh/.350kWh/mile = 14.3 miles.

 

[SwampNut]

We have a bunch of charges that will happen with or without the car, so I don't count those or distribute them into the charging cost. But I do need to take a second look at any taxes that are a multiplier from the kWH used.

I have a Sense whole house energy monitor, so I take the usage and dollars from there.

 

[Johnny Vector]

Dedicate Trip B to “Monthly Total,” and use a reminder to every first of the month put the numbers into a spreadsheet and reset. Then multiply the monthly kWh by your rate to figure out monthly cost (and cost per mile).

NERRRRD!!

That's... not at all what I do. No sir.

In truth I don't, because in my case the cost is all about the nonlinearity when I cross zero at the end of the year. That changes my cost/kWh from about 6 cents (when I'm a net exporter and they pay me only the generation rate) to about 14 cents (when I'm a net importer and they charge me that plus distribution rate, various taxes, and whatever other per-kWh charges they throw on there). Even worse is they true up at the end of April, and my big usage is heating, so I might go negative in March and have to pay for kWh even though I'll then make that up in April.

But aside from that, I totally hear you!

 

[EVer Hopeful]

Dedicate Trip B to “Monthly Total,”

I *think* (but haven't tried it yet) you can rename the trip

Pull up the card for Trip B and tap the three dots and see what happens

Let us know, and I'll try it later. I just can't get to it at the moment

 

[Rice&Curry]

Dusting off the Grammar School Physics memories here but if

Watts = Volts x Amps

and I have the HPWC on a 240v circuit set to 30A, which for the 80% rule is really a 24A pull, then I'm drawing

240 x 24 ==> 5760 Watts or 5.76 kW

and if I do that for an hour I will have used 5.76 kWh - might as well call that 6 kWh

and looking at my plan, I'm paying somewhere between 8.6 and 9.1 cents per kWh [1] (and 100% renewable ) so call that 9c per kWh


Therefore it costs me 54 cents an hour to charge my vehicle at home


Now all I need to figure out is how far I go on that amount of charge




[1] I change to a new provider every time the plan expires as the "new customer" rates are always better than the ones for existing customers - sort of a reverse loyalty program

Just to make things more interesting and more scientific , we need to factor in the efficiency factor for AC to DC conversion for charging the battery. May be a 0.95 or 0.9 efficiency factor should be used as a multiplier.

 

[Sophias_dad]

I *think* (but haven't tried it yet) you can rename the trip

Pull up the card for Trip B and tap the three dots and see what happens

Let us know, and I'll try it later. I just can't get to it at the moment

Yes, you certainly can.

 

[JimmySure]

I thought I was getting a deal here in Seattle paying 10 to 13 cents per kWh (mostly hydro, so 90% renewable), but damn is electricity cheap in TX and AZ.

My overall electric usage is probably up about 25% overall since buying the Tesla, but still peanuts compared to what I was paying for gas in my Range Rover Sport. Just for comparison, I used 1673 kWh from Aug 11 to Oct 11 (got the Tesla on Aug 13) for a total cost of $211.04 so 12.6 cents per kWh with all fees. I have driven the Tesla 2,600 miles to day, so probably 2,000 miles for the above statement.

Even assuming the Tesla has doubled my usage (which it has not) would put me at 5 cents per mile. More realistic is probably something close to 3 to 4 cents per mile. I will gladly pay this all day long...with a smile on my face.

 

[Zer0Her0]

I use Optiwatt to keep track of my charging costs. For 4 hours of charge at $.12/kWh, I paid $3.80. The cost per kWh is standard regardless of time per day. Another example, for a 3 hr 45 min charge at $.12/kWh, I paid $3.48.

Using the 14-50 delivering 32 amp max getting 31 mi/hr

 

[LoudMusic]

I thought I was getting a deal here in Seattle paying 10 to 13 cents per kWh (mostly hydro, so 90% renewable), but damn is electricity cheap in TX and AZ.

My overall electric usage is probably up about 25% overall since buying the Tesla, but still peanuts compared to what I was paying for gas in my Range Rover Sport. Just for comparison, I used 1673 kWh from Aug 11 to Oct 11 (got the Tesla on Aug 13) for a total cost of $211.04 so 12.6 cents per kWh with all fees. I have driven the Tesla 2,600 miles to day, so probably 2,000 miles for the above statement.

Even assuming the Tesla has doubled my usage (which it has not) would put me at 5 cents per mile. More realistic is probably something close to 3 to 4 cents per mile. I will gladly pay this all day long...with a smile on my face.

My electricity is 6.7c in the summer and 4.9c in the winter Yay for co-ops!

I'd really like to install solar on all my families' houses but it's just not worth it when our electricity is already so cheap.

 

[JimmySure]

My electricity is 6.7c in the summer and 4.9c in the winter Yay for co-ops!

I'd really like to install solar on all my families' houses but it's just not worth it when our electricity is already so cheap.

Had I stayed in California, I would have gone solar. The baseline rates were reasonable, but limits were WAY too low, so I was always triggering escalations that would run 30 to 40 cents per kWh once you hit the top tier. The ROI for solar was definitely there. Here in WA, my rates start at 10 cents per kWh and only go to 13 cents no matter how much I use. Totally not worth it when I'm paying about $100 per month for house and car. I can't imagine the ROI being there when your rates are half of that.

 

[ChrisMPK]

Our peak summer rate is $.53 with delivery charges, so yeah, I have solar. Even the evening (summer) rate is I think $.16 with delivery charges in So Cal. Fortunately I have access to commercial rates at my office and pay closer to $.05 most of the time. Effective cost per mile of electricity is I think eclipsed by cost per mile of tires.

 

[LoudMusic]

Our peak summer rate is $.53 with delivery charges, so yeah, I have solar. Even the evening (summer) rate is I think $.16 with delivery charges in So Cal. Fortunately I have access to commercial rates at my office and pay closer to $.05 most of the time. Effective cost per mile of electricity is I think eclipsed by cost per mile of tires.

That honestly hadn't crossed my mind. Tires cost more than electricity. I think maybe I'll try to take better care of the tires now ...

May I ask, what's your home solar setup like?