Really basic question here. I'm coming up on my second anniversary of buying my Model 3 and I'd like to get a sense for how much I've saved in fuel costs. The math on estimating what I would have spent on gas is easy. But I'm having a hard time figuring out how to estimate what I have spent on charging. Can someone help me out with this? Thanks.
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Calculating Fuel Savings
- Thread starter Brenkj
- Start date
Ideally you would use something like TeslaFi that captures all the charging and driving. You then have all the information necessary to calculate what you want.
Otherwise you could make a rough calculation from the kms (or miles) you drove, using your average consumption in wh/km (wh/mile) that you see in the car's trip computer. That would give you the kilowatt-hours you consumed. You then check your electricity bill to know how much you pay per kilowatt-hour and bingo. You should add 10% to your kWh consumption for charging losses. Now if you travelled and used superchargers you can look at your Tesla account to know how much you spent there. Just subtract that distance from your total kms (miles) before you compute home charging costs.
Otherwise you could make a rough calculation from the kms (or miles) you drove, using your average consumption in wh/km (wh/mile) that you see in the car's trip computer. That would give you the kilowatt-hours you consumed. You then check your electricity bill to know how much you pay per kilowatt-hour and bingo. You should add 10% to your kWh consumption for charging losses. Now if you travelled and used superchargers you can look at your Tesla account to know how much you spent there. Just subtract that distance from your total kms (miles) before you compute home charging costs.
Thanks for the response. According to my trip computer, my kw/mi. for the life of the car is 266. If I multiply that by 20,000 (my approx. mileage when I hit the 2-year mark in a couple weeks) I get 5,320,000. According to my electricity bill, our rate is $0.113439 per kW/Hr. When I multiply those two numbers I get 603,495. I know that can't be right. What am I doing wrong? Thanks.
[Edit:] Wait a sec. That's really off. I have something wrong too.
[Edit:] Oh, I got it. It is multiply, but when you were multiplying by 266, that is watt hours. But then you treated the answer as if it was kilowatt hours. That's a 1,000 X factor bigger. So it's actually 5,320, not 5,320,000. So 5,320 kWh of electricity at 11 cents is $585.
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Just to make things easy, I used avg. gas mileage of 20 mpg. My old car was a 5-Series, which is probably a little better mileage, but there have been many times the last two years when we drove my Model 3 instead of my wife's SUV, which is obviously lower mpg. 20,000 miles divided by 20 mpg = 1000 gallons. Multiplied by an avg. of $2.50 per gallon = $2,500. So I've save around $2,000 in 2 years. This doesn't include the savings from not having to get a couple of tuneups, which would've been another $200 or so each. Not too shabby. I can't wait to tell my wife "I told you so" about the savings we would see from buying a Tesla.
you could just use an online calculator rather than making a thread and asking us to do that math for you...not trying to be a PIA
but more of in the future, the more you know.
something like this is fine, up to your liking to find one that fits your preference.
Electric car calculator, cost per mile and cost per km calculator
but more of in the future, the more you know.
something like this is fine, up to your liking to find one that fits your preference.
Electric car calculator, cost per mile and cost per km calculator
The above posts consider only driving energy. Not only does the car consume energy while sitting, but charging efficiency is also a factor (which was mentioned)
From post history it seems you use the NEMA 14-50 adapter, so your charging efficiency is around 91%.
I don't know the configuration of your car or your habits, so the rest is an assumption. If I assume a 30W standby draw (this is fairly conservative),
So in your case, an additional 10% or so is used for standby. This could be slightly better in theory, but it could also be significantly worse. For example, you're in TX -- Cabin Overheat Protection may be adding to that substantially if you have it enabled.
Now, factoring in charging losses,
That brings the projected yearly cost, if entirely charged at home at $0.113439, to $364.35/year.
I suspect the actual cost is closer to the $380-$450. This can be narrowed down with a bunch of details (Sentry Usage, Summon usage, Cabin Overheat Protection usage, whether or not it's in a garage, whether or not that garage is somewhat temperature buffered, etc.) but can get a bit exhausting. The "worst case" scenario would be around $700/year.
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Note that tools like TeslaFi aren't really accurate at tracking "wall energy" (vs. what your car uses). Without boring anyone, there are multiple reasons for this that they can't really do anything about.
The way I track energy usage from the car is by always starting a charge at 12am. My electricity provider gives hourly usage stats, so I know my baseline energy usage pre-Tesla and simply see what additional energy the Tesla takes. If you can do this with you provider, it'll give you a great historical picture.
Otherwise, there's energy meters you can get on Amazon cheaply and are easy to install (may need an electrician briefly) for the future. Assuming the unit is good, you can't get a much more accurate picture of energy usage than this method.
From post history it seems you use the NEMA 14-50 adapter, so your charging efficiency is around 91%.
I don't know the configuration of your car or your habits, so the rest is an assumption. If I assume a 30W standby draw (this is fairly conservative),
30W * 24h/day * 365days/year = 262800Wh / year = 262.8kWh / year for standby
Implying you drive about 10,000 mi/year at an average of 266 Wh/mi as you state,
10,000mi/year * 266Wh/mi = 2660000Wh / year = 2660kWh / year for driving
So in your case, an additional 10% or so is used for standby. This could be slightly better in theory, but it could also be significantly worse. For example, you're in TX -- Cabin Overheat Protection may be adding to that substantially if you have it enabled.
Now, factoring in charging losses,
Car Energy Total / Charging Losses = Total Energy From Wall
(262.8kWh + 2660kWh) / 0.91 = ~3212kWh / year
(262.8kWh + 2660kWh) / 0.91 = ~3212kWh / year
That brings the projected yearly cost, if entirely charged at home at $0.113439, to $364.35/year.
I suspect the actual cost is closer to the $380-$450. This can be narrowed down with a bunch of details (Sentry Usage, Summon usage, Cabin Overheat Protection usage, whether or not it's in a garage, whether or not that garage is somewhat temperature buffered, etc.) but can get a bit exhausting. The "worst case" scenario would be around $700/year.
---
Note that tools like TeslaFi aren't really accurate at tracking "wall energy" (vs. what your car uses). Without boring anyone, there are multiple reasons for this that they can't really do anything about.
The way I track energy usage from the car is by always starting a charge at 12am. My electricity provider gives hourly usage stats, so I know my baseline energy usage pre-Tesla and simply see what additional energy the Tesla takes. If you can do this with you provider, it'll give you a great historical picture.
Otherwise, there's energy meters you can get on Amazon cheaply and are easy to install (may need an electrician briefly) for the future. Assuming the unit is good, you can't get a much more accurate picture of energy usage than this method.
AlanSubie4Life
Efficiency Obsessed Member
Excellent summary.
In terms of comparison to a gasoline car, as @Brenkj wanted to do, we could convert these numbers to cents per mile:
$365/yr/10e3 miles/yr = 3.65 cents/mi
(You can equivalently take the cost per kWh, and multiply by average Wh/mi, multiplied by 21% - 21% is a fudge factor; could be much higher (40-50% is possible in colder climates with the car stored outside) as @camalaio says. Primary determinants of the fudge factor are: charging setup (10% loss is a good estimate, can be as high as 30% for 120V charging), vampire losses (dependent on miles driven per year - higher mileage lowers this, 10% is typical) & feature use losses ):
$/kWh * (Driving efficiency (kWh/mi) * 1.21) = $0.1134/kWh *0.266kWh/mi*1.21) = 3.65 cents/mi
Whereas a 30mpg gas car with $3/gallon gas is:
Price per gallon * gallons per mile = Price/gallon / MPG = $3/gallon / 30mpg = 10 cents/mi
Obviously doesn't account for other possible savings. Just an energy cost comparison.
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CertLive
Member
If you have supercharged then check under your Tesla account it will have the session charge costs. Then add that to other apps for home charging etc. This should give you total price and kwh put in, most apps allow set of price too. Also check the odometer total it might tell you total used by the car to get the reference closer. Every time I have worked it out it is drastically less money than fuel. Long trips in the UK end up costing no more than a coach ticket. Esp when you go to Scotland where its free to charge (Beautiful country).
AlanSubie4Life
Efficiency Obsessed Member
That is because you do not live in the US of A, where the buffalo roam, the oil flows freely, and taxes are sinful.
In quite a few locations here (ironically, where Teslas have the highest prevalence), the energy costs for running a Tesla are similar to or exceed fueling costs for a reasonably efficient (30mpg+) gasoline vehicle. Solar generation is important to have the EV fueling costs make sense in these locations (fortunately in these locations, solar usually makes a lot of sense).
TheRFMan
Member
LOL... even comparing here in Canada (Ontario), electricity costs are about 10c/kWh off-peak, and fuel is hovering around $1/liter ($3.80/gallon). All Canadian dollars, multiply by 0.75 to get close to USD. Gas is not that much more expensive than in the USA, but electricity is not too bad (lots of hydro-electric and large-scale nuclear here). By Canadian standards, electricity here is expensive. In Quebec, it's closer to 5-6c/kWh.
At those rates, it is much cheaper to drive on electricity than gasoline. Solar is not particular helpful here, the panels would be covered in snow 4-5 months of the year
AlanSubie4Life
Efficiency Obsessed Member
LOL...
At those rates, it is much cheaper to drive on electricity than gasoline. Solar is not particular helpful here, the panels would be covered in snow 4-5 months of the year
True. Many people without solar in California pay 40-50 cents per kWh. And those are good old-fashioned STRONG, AMERICAN cents.
Fortunately, a good-sized solar array can solve this here.
However, even with solar, the last couple months my marginal rate has gone to ~48 cents/kWh. That’s because it has been so hot, so my electrical usage with AC went to net 600kWh per month, meaning I paid 150kWh or so at this elevated rate, even though I generated 500kWh in the same period.
At my typical consumption of 300Wh/mi, that is:
$0.48/kWh*300Wh/mi*1.3 = 19 cents/mi.
Break even is gas at ~$5.60/gallon.
There are tons of different tariffs (rate plans) available to try to optimize your bill with Time Of Use, etc., but there is no free lunch - you can get cheap charging at night, but then you pay through the nose during the day with AC use. The only way to really be in the clear (typically) is to have about a 6-8 kW solar system. You can usually then avoid the punitive rates; it’s hard to get to the high marginal rates with that much production.
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I've kept detailed track of my actual consumption (as per the onboard computer) vs. total kWh added as per TeslaFi, and I can tell you that the extra consumption is closer to 25% for me. This is WITHOUT extensive use of sentry but does include a fair bit of idling and cabin cooling / pre-heating. Doge Mode is also on quite a bit.
In other words, I may have consumed 100 kWh of battery to drive, but my total consumption is 125 kWh if I include everything else.
AlanSubie4Life
Efficiency Obsessed Member
Just... wow.
6.5 cents per kWh here in the beautiful red rock desert.
Lake Foul (
) (Glen Canyon) and also Lake Mead (Hoover) are doing a lot of work for you here, probably. 60% hydroelectric generation in the Northwest Power Pool area.It has been years since I researched it, so I'm glad to hear that a lot of the power going into my car is hydroelectric. Many, many years ago, a lot of our power here came from the Page, AZ Navajo Generating Station, which was/is(?) (not sure if it's still in operation, actually) coal fired.Lake Foul (
They got their coal from a huge Peabody Coal Company mine near Kayenta.
AlanSubie4Life
Efficiency Obsessed Member
It's apparently not in operation anymore. The 60% is for a very large area (NWPP), so for St. George the proportion may be lower. I don't know really where you get your power from, exactly, to be honest. But hydroelectric seems to be associated with very low rates, so I am assuming that is a big portion of it. I could be wrong.
https://www.ucsusa.org/sites/default/files/2020-05/evs-cleaner-than-gasoline.pdf
The very high MPG values in the different regions are associated with use of renewables (hydro/wind/solar).
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