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I can’t seem to find a true answer.

maverick3n1

Member
Apr 30, 2019
44
27
Oceanside
I’ve seen some posts that power draw while in park is not calculated in your power usage (IE, using the AC in park etc), but it seems people are saying it is calculated in your kWh used while driving. I’m getting conflicting results on my Tesla, and trying to figure out what the deal is.

2019 Model 3 Performance with 22k miles on it. To my understanding, stock is 75kwh battery.

It was charged to 90% at the beginning of my 2 hour venture with AC running 90% of the time. Outside temp was average 90-95 degrees, humid.

End trip, down to 51%, so 39% of battery used. According to miles since last charged: 76.4 miles, 24kwh, 320wh/mile (quite a bit of hill/mountainous terrain)

If 39% of the battery is 24kwh, that means 100% of the battery is only 61.5kwh. This leads me to believe that the reported power draw is not including accessories like headlights, AC, sound system and so on (it was getting dark so the headlights were on the entire time)

Am I correct that it’s not including those accessories, or should I be concerned?
 

Candleflame

Active Member
Mar 9, 2015
3,324
1,794
QLD, Australia
I’ve seen some posts that power draw while in park is not calculated in your power usage (IE, using the AC in park etc), but it seems people are saying it is calculated in your kWh used while driving. I’m getting conflicting results on my Tesla, and trying to figure out what the deal is.

2019 Model 3 Performance with 22k miles on it. To my understanding, stock is 75kwh battery.

It was charged to 90% at the beginning of my 2 hour venture with AC running 90% of the time. Outside temp was average 90-95 degrees, humid.

End trip, down to 51%, so 39% of battery used. According to miles since last charged: 76.4 miles, 24kwh, 320wh/mile (quite a bit of hill/mountainous terrain)

If 39% of the battery is 24kwh, that means 100% of the battery is only 61.5kwh. This leads me to believe that the reported power draw is not including accessories like headlights, AC, sound system and so on (it was getting dark so the headlights were on the entire time)

Am I correct that it’s not including those accessories, or should I be concerned?

Stock is around 78 to 78.5kwh of which 4.5% (3.5kwh) is reserved as a buffer which should be accessable with normal driving sub 0% if the BMS does a good estimate. Rumours has it that there is a 1.5 to 2.5kwh brick protection as well for a 80kwh pack with 4416 cells.

Theres a few people who have obtained the 2170 cells and done some discharging and a cell can do slightly more than 18wh of work when brand new for a total capacity of 4416 x 18wh = 79.5kwh which fits with the 80kwh pack theory.

So that leaves you with around 75kwh from 0 -100% and if the BMS gets it right you can go below 0% to around -4.5%.
Power draw when in park is not calculated into consumption but it is when driving.
The only odd thing with the Model 3 is that the 3's power meter only shows you the energy the motor is pulling, not the energy the car is pulling (unlike the pre-AP Model S which would show you the powerdraw of the whole car even when ideling).
Also heat loss from the battery is not accounted for which is maybe 500W-1kw at 120km/h for a full discharge.

your calculation is a bit weird but tbh if you want to see how many kwh you got in your battery just set your display to distance and see what it is at 100%, either via multiplication or by just going into the app and setting chargelevel to 100%.
You can then multiple kms by 150 to see how many wh the BMS thinks is accessable which is fairly accurate.

The only real way to know how much charge your battery can hold is to do a full charge from i.e. 0 - 100% and see how many kwh you can put in the battery - something like teslafi can monitor that for you.
 

Phlier

Bluebird
Jun 12, 2019
1,976
3,550
Utah
@Candleflame 's post is spot on.

Remember that when you are in percentage of battery remaining mode, the BMS is showing you the percentage of available power remaining, based on what it thinks your battery is capable of holding, NOT based on what the pack was rated at when it was new. That's why you need to have it show you miles remaining. I can't remember what the Wh/m constant is for the Performance Model 3 off the top of my head, but a little digging here will find that figure for you. Once you find that number, you can use it to multiply it by the "Miles Remaining." As @Candleflame said, doing so will give you the capacity that the BMS thinks your battery is capable of holding. Why Tesla doesn't just show us this information is a bit of a head scratcher...I'm sure it would cut down on a ton of calls to their customer support personnel about battery degradation.

I'll do a little digging and find that number for you... I know it's somewhere in my rather long list of "Watched Threads."

I know @AlanSubie4Life has the numbers for all the Model 3's. Maybe we can get him to pop in here and list them for us? :)
 
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camalaio

Active Member
May 28, 2019
1,483
2,181
Vernon, BC, Canada
Trip meter usage absolutely includes auxiliary power while driving like climate control, headlights, 12V battery charging, etc. As far as I can tell, it just measures the power output of the high voltage battery, which includes nearly everything. What it doesn't include averages out over time and is negligible anyways (the difference between the 12V battery being charge and/or supplying power).

This is most obvious in winter conditions. Turn on the heater and watch your Wh/mi soar.

Now, to your numbers. More accurately, the trip meter says it used 24448Wh (distance times efficiency). If and only if you did this trip straight and measured those percentages immediately at the start and end (with no cabin preconditioning) can you conclude that your reported usable capacity is somewhere in the range of 61.1kWh and 64.3kWh (variance due to rounded percentages from the car). As others mentioned, there's about a 4.5% buffer below "0%", making the total capacity somewhere in the range of 64.0kWh and 67.4kWh. This puts you around to 13.1% to 17.5% reported degradation. (rated new total capacity is about 77.5kWh, extrapolating from the car's numbers and the buffer amount).

The best way to confirm what the car is reporting is to switch to range display instead of percent, and drag the slider in the app to 100% and see what it reports. This works best if the battery is somewhat warm, as being below room temp will impact it noticeably. If it puts you between 251mi and 265mi of range at 100%, then the above calculations were correct and you didn't have any significant unexpected energy drain outside your trip meter. If you missed energy, it will report more range and you have less reported degradation, which would be nice. If you missed energy, you probably did something like precondition the cabin?

Stock is around 78 to 78.5kwh of which 4.5% (3.5kwh) is reserved as a buffer which should be accessable with normal driving sub 0% if the BMS does a good estimate. Rumours has it that there is a 1.5 to 2.5kwh brick protection as well for a 80kwh pack with 4416 cells.

Theres a few people who have obtained the 2170 cells and done some discharging and a cell can do slightly more than 18wh of work when brand new for a total capacity of 4416 x 18wh = 79.5kwh which fits with the 80kwh pack theory.

So that leaves you with around 75kwh from 0 -100% and if the BMS gets it right you can go below 0% to around -4.5%.
Power draw when in park is not calculated into consumption but it is when driving.
The only odd thing with the Model 3 is that the 3's power meter only shows you the energy the motor is pulling, not the energy the car is pulling (unlike the pre-AP Model S which would show you the powerdraw of the whole car even when ideling).
Also heat loss from the battery is not accounted for which is maybe 500W-1kw at 120km/h for a full discharge.

your calculation is a bit weird but tbh if you want to see how many kwh you got in your battery just set your display to distance and see what it is at 100%, either via multiplication or by just going into the app and setting chargelevel to 100%.
You can then multiple kms by 150 to see how many wh the BMS thinks is accessable which is fairly accurate.

The only real way to know how much charge your battery can hold is to do a full charge from i.e. 0 - 100% and see how many kwh you can put in the battery - something like teslafi can monitor that for you.

Fantastic post, but a minor correction.

The power meter below the gear indicator does in fact display auxiliary usage. It is usually just dwarfed by locomotive needs. You can see this if you enable the heater on max while in drive and stopped - it'll flicker a small amount of the black bar.

Highway travel, coasting on flat ground, requires somewhere near 15kW of power and still only shows a very small amount of the black bar. This is way, way more than you can pull in normal conditions with anything other than the motors. AC usage settles to about 1kW normally. Idle power of the car (lights on, in drive) is a bit above 500W. These are tiny in comparison.

I'll do a little digging and find that number for you... I know it's somewhere in my rather long list of "Watched Threads."

I just Google "alansubie4life constants", and voila, first result every time.

The thing I'm not certain of is if the numbers changed via updates, especially the max rated range. It's a bit more work to determine.
 

Phlier

Bluebird
Jun 12, 2019
1,976
3,550
Utah
I just Google "alansubie4life constants", and voila, first result every time.
Thank you, thank you, thank you! :)

I went through my Watched Threads list for 20 minutes earlier today, and gave up. Don't know why I didn't think to just Google it.

The knowledge that you and other members here share with us is greatly appreciated.
 

Phlier

Bluebird
Jun 12, 2019
1,976
3,550
Utah
@maverick3n1 This thread is definitely worth taking 20 minutes to look at. Chances are that thread will have an answer to pretty much any battery related question you could come up with.

It should really be a sticky.
 
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Candleflame

Active Member
Mar 9, 2015
3,324
1,794
QLD, Australia
Trip meter usage absolutely includes auxiliary power while driving like climate control, headlights, 12V battery charging, etc. As far as I can tell, it just measures the power output of the high voltage battery, which includes nearly everything. What it doesn't include averages out over time and is negligible anyways (the difference between the 12V battery being charge and/or supplying power).

This is most obvious in winter conditions. Turn on the heater and watch your Wh/mi soar.

Now, to your numbers. More accurately, the trip meter says it used 24448Wh (distance times efficiency). If and only if you did this trip straight and measured those percentages immediately at the start and end (with no cabin preconditioning) can you conclude that your reported usable capacity is somewhere in the range of 61.1kWh and 64.3kWh (variance due to rounded percentages from the car). As others mentioned, there's about a 4.5% buffer below "0%", making the total capacity somewhere in the range of 64.0kWh and 67.4kWh. This puts you around to 13.1% to 17.5% reported degradation. (rated new total capacity is about 77.5kWh, extrapolating from the car's numbers and the buffer amount).

The best way to confirm what the car is reporting is to switch to range display instead of percent, and drag the slider in the app to 100% and see what it reports. This works best if the battery is somewhat warm, as being below room temp will impact it noticeably. If it puts you between 251mi and 265mi of range at 100%, then the above calculations were correct and you didn't have any significant unexpected energy drain outside your trip meter. If you missed energy, it will report more range and you have less reported degradation, which would be nice. If you missed energy, you probably did something like precondition the cabin?



Fantastic post, but a minor correction.

The power meter below the gear indicator does in fact display auxiliary usage. It is usually just dwarfed by locomotive needs. You can see this if you enable the heater on max while in drive and stopped - it'll flicker a small amount of the black bar.

Highway travel, coasting on flat ground, requires somewhere near 15kW of power and still only shows a very small amount of the black bar. This is way, way more than you can pull in normal conditions with anything other than the motors. AC usage settles to about 1kW normally. Idle power of the car (lights on, in drive) is a bit above 500W. These are tiny in comparison.



I just Google "alansubie4life constants", and voila, first result every time.

The thing I'm not certain of is if the numbers changed via updates, especially the max rated range. It's a bit more work to determine.

WHAAAATTTT IM LITERALLY GONNA GO TO MY CAR TO FIND OUT NOW.

edit: Ha, it totally does. I guess it uses a linear scale and not a logarithmic one like the old Model S so its hard to see - and useless anyway without labeling.
 

Candleflame

Active Member
Mar 9, 2015
3,324
1,794
QLD, Australia
You guys are reporting the KWh available usage and size of the battery too high. It's more like 72 to 73KWh out of a 75KWh battery.

Within a few months you will get 1-2% degradation which will leave you with around 73.5kwh of useable wattage. So with 500watt heatloss driving at i.e. 90kmh you should be able to get around 73kwh out of a battery.

A new Model 3 battery has 77.5-78.5kwh with a set 4.5% buffer which you cannot see below 0%.
To get rated range you need to stick to exactly 150w/km which for the 499km range works out to 74.8kwh.

I have done one 5 - 100% charge on my Model 3 when it had like 1% degradation and it amounted to like 74.3kwh dumped into the battery extrapolated for 0 - 100% charge if I remember correctly.
 
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maverick3n1

Member
Apr 30, 2019
44
27
Oceanside
@Candleflame 's post is spot on.

Remember that when you are in percentage of battery remaining mode, the BMS is showing you the percentage of available power remaining, based on what it thinks your battery is capable of holding, NOT based on what the pack was rated at when it was new. That's why you need to have it show you miles remaining. I can't remember what the Wh/m constant is for the Performance Model 3 off the top of my head, but a little digging here will find that figure for you. Once you find that number, you can use it to multiply it by the "Miles Remaining." As @Candleflame said, doing so will give you the capacity that the BMS thinks your battery is capable of holding. Why Tesla doesn't just show us this information is a bit of a head scratcher...I'm sure it would cut down on a ton of calls to their customer support personnel about battery degradation.

I'll do a little digging and find that number for you... I know it's somewhere in my rather long list of "Watched Threads."

I know @AlanSubie4Life has the numbers for all the Model 3's. Maybe we can get him to pop in here and list them for us? :)

Sorry for coming back so late, but I decided to play with settings, jump back and forth between percentage battery remaining and how many miles remaining and so on. So here is my current stats, what I've figured out, and I still think there may be issues, but would love everyone's feedback.

2019 Tesla Model 3 Performance. Current Mileage 26,588.

Always charge to 90% with exception of less than 10 times since purchase of the vehicle for a few long trips. Have supercharged roughly 4 times, and not beyond 90%. Daily charger used is the portable charger it comes with, plugged into a 208v 50 amp outlet.

I've found that 90% charge, when changing settings between percentage and miles left, comes out to 254 miles remaining (per the display, not actual). I've run the battery down to close to 0, then charged it back up. Same results. This seems fairly consistent. That said, each time I drive home, I'm sometimes under 250 Wh/mile and sometimes over. Since the vehicle is rated at 250 Wh/mile, I have been waiting for the "perfect score". Today, when I left my place of business, I was at 90% charge and the vehicle listed a 254 mile range. I drove it 39.3 miles and the report shows, since last charge, I drove 10kWh and was exactly at 250Wh/mi. Remaining range, 209 miles (I didn't change it back to percentage to check that).

So before my trip, I had 254 miles.. subtract 39.3 and I should have 214.7 miles remaining. Instead, I had 209. I was driving during the evening and it was fairly cool out, so I had windows down, no AC on, but it was evening, so headlights were on, music was playing, and I had my cell phone charging on a wireless charge adapter I got for the dock station. No seat heaters or anything else.

From my understanding, my year/model vehicle was rated at 310 mile range going 250Wh/Mile. Based on the range listed of 254 at 90%, that means 100% would be 282 miles. That tells me I have a 9% battery degradation, when everything I'm reading says that Tesla's been reporting a 10% battery degradation at 150k miles. I'm far from there! In addition, where did the 5-6 miles go that I lost when I got an exact 250Wh/mi? That makes the mileage available even less.

Lastly, I'm a bit confused as to how they are calculating the MPGe saying that they are the most energy efficient vehicles...

Sited from: Most of Tesla lineup gets a range boost: up to 353 miles for Model 3, 371 miles for Model X "The Model 3 was already the most energy-efficient passenger vehicle on the United States market, with the Standard Range Plus achieving 141 MPGe combined (148 MPGe city, 132 MPGe highway)."

This vehicle is cost effective when it comes to energy consumption, because I charge it at my restaurant, where I pay around $0.09/Kwh. At my house, electricity is an average of $0.50/kwh. At 10Kwh, for 39.3 miles, I'd pay $5 in electricity if I were the average homeowner. That's 28 miles for $3.56 which is about what a gallon of premium gas costs here in Southern California. I have 110% solar coverage on my house, but you can only utilize the solar plan or the electric vehicle plan. You can't use both, so if I switch, I take a huge loss on the solar and get charged a lot more for usage during the time my solar isn't generating power, in exchange for lower car charging prices from midnight to 6am, as I lose my bonus credit from overgeneration during the day which is currently what 100% offsets my evening usage, so I'm screwed either direction.
 
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jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
10,873
12,592
Riverside Co. CA
you pay 0.50 usd/kwh at your house? wth?

I re read his post, and see he is not on a Time of use plan. Even still i doubt he is "averaging" 50 cents a kWh. That would be the charge for the highest tier, and if he is using enough electricity to have "most" of his usage be at that tier, he should think about switching... but he isnt using the bulk of his electricity at that rate because he has solar with net metering.

TL ; DR the "everage 50 cents a kWh" statement is used as an example but is not what he is paying.
 
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AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
10,918
13,698
San Diego
2019 Tesla Model 3 Performance. Current Mileage 26,588.
I've found that 90% charge, when changing settings between percentage and miles left, comes out to 254 miles remaining (per the display, not actual).

You have 282 rated miles at a full charge, approximately.

Your car has 245Wh/rmi*282rmi = 69.1kWh remaining at 100%. When it was new you had about 78kWh.

So that is 11.5% capacity loss, which is not all that unusual at 26k miles. Not clear exactly how old your vehicle is (could be nearly two years old if it is a 2019).

Since the vehicle is rated at 250 Wh/mile,

It's not. For parity, you need to do about 228-232Wh/mi. This will give mile for mile rolloff. This is because there is a buffer of 4.5%, so your 100% to 0% charge only contains 95.5% of your 69.1kWh, which is 66kWh. 66kWh/282rmi = 234Wh/rmi. The remaining discrepancy (230Wh/rmi vs. 234Wh/rmi) is uncounted loss (heat loss, etc.).

Again: you only have 66kWh between 100% and 0%. When the car was new it had 74.5kWh there. And about 78kWh total.

I was at 90% charge and the vehicle listed a 254 mile range. I drove it 39.3 miles and the report shows, since last charge, I drove 10kWh and was exactly at 250Wh/mi. Remaining range, 209 miles (I didn't change it back to percentage to check that).
So before my trip, I had 254 miles.. subtract 39.3 and I should have 214.7 miles remaining. Instead, I had 209. I

This is the wrong calculation. Taking your numbers at face value: 250Wh/mi*39.3mi = 9.8kWh

9.8kWh/230Wh/rmi = 42.6rmi

254rmi-42.6rmi = 211.4rmi.

You say you had 209rmi. There are rounding errors here which can easily explain the remaining 2 mile discrepancy, as well as losses while sitting stationary (which are not counted on the trip meter). It's a combination of both. Inherently, the "230Wh/rmi" value for discharge is just a close approximation (the 245Wh/rmi is NOT an approximation). There are a lot of factors on a given drive than can lead to a somewhat different calculated value (generally you can calculate 228Wh/rmi to 232Wh/rmi if you're careful about the data gathering).

This info is all in the 2020, 2019, 2018 Model 3 Battery Capacities & Charging Constants thread. (It's a sticky.)

You can't use both, so if I switch, I take a huge loss on the solar and get charged a lot more for usage during the time my solar isn't generating power, in exchange for lower car charging prices from midnight to 6am, as I lose my bonus credit from overgeneration during the day which is currently what 100% offsets my evening usage, so I'm screwed either direction.

I'm not really following. I live in San Diego, so I have SDG&E. I think you do as well. It is definitely true that if your home energy use is already high, even with solar, the marginal cost of charging your vehicle can get extremely high.

But there are TONS of tariffs/rate plans. In the end there is no getting around using a lot of energy. If you do use a lot of energy (for AC and for the car), it is going to cost you. You can pay for a plan ($6 per month?) that gives you about 10 cents per kWh at night. But rates will still be very high during the day if you exceed your solar generation. And they have changed the highest hours to make the payback of solar less beneficial.

If you're doing net metering, yet you get into the highest marginal bracket due to enormous consumption, yes, charging your car is going to get very expensive. Also AC will be expensive in this case (in marginal terms).

I have solar, and use a plan which gives me 18 cents per kWh at night, and caps my daytime usage charges at 28 cents per kWh. Unless I exceed about 450kWh in a month - at that point the rates go way up during the day to the ~50 cents/kWh.

Anyway, the car is one of the most efficient on the road in terms of energy usage, not necessarily cost. The cost depends on your rates.
 
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maverick3n1

Member
Apr 30, 2019
44
27
Oceanside
You have 282 rated miles at a full charge, approximately.

Your car has 245Wh/rmi*282rmi = 69.1kWh remaining at 100%. When it was new you had about 78kWh.

So that is 11.5% capacity loss, which is not all that unusual at 26k miles. Not clear exactly how old your vehicle is (could be nearly two years old if it is a 2019).



It's not. For parity, you need to do about 228-232Wh/mi. This will give mile for mile rolloff. This is because there is a buffer of 4.5%, so your 100% to 0% charge only contains 95.5% of your 69.1kWh, which is 66kWh. 66kWh/282rmi = 234Wh/rmi. The remaining discrepancy (230Wh/rmi vs. 234Wh/rmi) is uncounted loss (heat loss, etc.).

Again: you only have 66kWh between 100% and 0%. When the car was new it had 74.5kWh there. And about 78kWh total.




This is the wrong calculation. Taking your numbers at face value: 250Wh/mi*39.3mi = 9.8kWh

9.8kWh/230Wh/rmi = 42.6rmi

254rmi-42.6rmi = 211.4rmi.

You say you had 209rmi. There are rounding errors here which can easily explain the remaining 2 mile discrepancy, as well as losses while sitting stationary (which are not counted on the trip meter). It's a combination of both. Inherently, the "230Wh/rmi" value for discharge is just a close approximation (the 245Wh/rmi is NOT an approximation). There are a lot of factors on a given drive than can lead to a somewhat different calculated value (generally you can calculate 228Wh/rmi to 232Wh/rmi if you're careful about the data gathering).

This info is all in the 2020, 2019, 2018 Model 3 Battery Capacities & Charging Constants thread. (It's a sticky.)



I'm not really following. I live in San Diego, so I have SDG&E. I think you do as well. It is definitely true that if your home energy use is already high, even with solar, the marginal cost of charging your vehicle can get extremely high.

But there are TONS of tariffs/rate plans. In the end there is no getting around using a lot of energy. If you do use a lot of energy (for AC and for the car), it is going to cost you. You can pay for a plan ($6 per month?) that gives you about 10 cents per kWh at night. But rates will still be very high during the day if you exceed your solar generation. And they have changed the highest hours to make the payback of solar less beneficial.

If you're doing net metering, yet you get into the highest marginal bracket due to enormous consumption, yes, charging your car is going to get very expensive. Also AC will be expensive in this case (in marginal terms).

I have solar, and use a plan which gives me 18 cents per kWh at night, and caps my daytime usage charges at 28 cents per kWh. Unless I exceed about 450kWh in a month - at that point the rates go way up during the day to the ~50 cents/kWh.

Anyway, the car is one of the most efficient on the road in terms of energy usage, not necessarily cost. The cost depends on your rates.


So to clarify a few things. First, the electricity usage graph in the vehicle lists "rated" Wh, and it's highlighted at 250. If I go below 250, the line drops below the rated. Above, and it goes above the rated, which is why I was under the impression that 250kwh is the "goal" to get the rated full range of the vehicle. It doesn't make sense, if you need to be closer to 240wh to get what they are showing as 250...

As for SDGE, yes, I'm with SDGE. The plan I'm on is designed with solar in mind. YTD, I've over generated 761 Kwh (I don't currently charge my vehicle at home). My rate is $0.31/kwh for the power, and $0.19/kwh for delivery for a total of $0.50/kwh. If I switch to the EV-TOU5 you are speaking of, I get the lower rate from midnight to 6am, however, my overgenerated power is washed out as I've been informed by SDGE. I can have one or the other. Not both. Currently, it's Kwh for Kwh. So if I use an excess of 250kwh one month during peak time, but generate an excess of 250kwh during non peak time, the two wash eachother out. If however, I go to the EV-TOU5 plan, with those same details, I pay the price of the 250kwh during peak time ($0.50/kwh or $125), and then I get credit of something along the lines of $0.03/kwh for the overgenerated power or $7.50 credit, so my bill is $117.50 not including the electricity used from 12am-6am charging the car, and the $16 plan charge. I am in a TOU plan as well, but even with the ToU plan, and on the bill I'm referencing, I only used an excess of 203kwh during peak time, my off peak time is $0.05/kwh for the electricity, and $0.19/kwh for delivery. Still expensive if I overdraw whatever I generate, as you know they will apply my overgeneration to the cheapest Kwh first, so I'll be stuck paying for the peak Kwh rather than the super off peak.
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
10,918
13,698
San Diego
and it's highlighted at 250.

It doesn't make sense, if you need to be closer to 240wh to get what they are showing as 250...

That’s correct, it does not make sense. The line is always 5Wh/mi above the charging constant. I do not know why. But it doesn’t matter. It does work out to 77.5kWh which is about what you start with, but remember that includes the 4.5% of your energy which exists below 0%. And that relationship falls apart once you start to lose capacity. In any case, the line position is hard to rationalize.

My numbers are correct. If you don’t believe me, measure it. You’ve already effectively done this, of course! You’ll find that the 228-232Wh/rmi value works really well as long as you measure carefully and minimize rounding error.



As for SDGE, yes, I'm with SDGE. The plan I'm on is designed with solar in mind.

Yeah; if you are not planning to change your use habits, I would use the billing simulator options from SDG&E and pick whatever one they say is cheapest for you.

But probably what you have is optimal for your current use. If you started charging at home a different plan might be optimal.

As I said, there is not any getting around using a lot of energy. The solution is to have about 8kW of solar generation - that will be enough for most medium size houses and support about one EV. Psychologically, it makes sense to go big on solar, in my opinion. You don’t want to pay a lot and then still be paying an electric bill (even though that may actually be optimal).
 
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