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Monthly power use question

JindoFuzz

Member
Feb 26, 2021
92
92
Portland, OR
Hi everyone. I have a dumb question. I purchased my LR on March 26. I just received my first post-purchase electric bill, through April 14 for 19 days of ownership. I leave the car plugged in with sentry on, and charged at home for about 500 miles of driving in that time (plus 200 miles on a supercharger). My usage for this month was around 300 kWh higher than the same month’s bill in 2020. The mileage is responsible for 125kwh of that based on 250 wh/mi consumption. The remaining 175 kWh delta pencils out to around 9.2 kWh/day, or about 380 watts per hour. That seems high to me, even though I left sentry mode on the whole time. Am I missing something?

I’m charging on a 110v plug until my wall charger is installed, so inefficiency is part of this. Once I have the charger installed I’ll be able to track the usage more closely, and eliminate other variable usage from the calculations. But for now, it seems like the car is drawing a LOT of power.
 

GtiMart

Member
Nov 13, 2019
851
690
Quebec City, Canada
You seem to be assuming the car's consumption at 250wh/m. You could look in your car and see what your actual consumption was.
On 120V, charging losses are fairly high, and it keeps your car awake for a long time as it charges very slowly. Sentry will also keep your car awake. While awake, the car will consume in the area of 250-300w to run computers, pumps etc. When it sleeps, this can go down to around 20-25w.
 
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Reactions: lUtriaNt

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
8,812
9,757
Riverside Co. CA
An easy number to look at, is sentry mode uses between 1 and 2 "miles" of electricity every hour, so between 24 and 48 "miles" a day, just sitting there.

if you take the low number of 1 mile per hour, 24 miles per day (but its likely more than that), take your 19 days and multiply by 24. 19 X 24 is 456 "miles" of energy you used just sitting there with sentry on 24 X 7 (minimum, its likely more).

Or, said another way, you probably used more energy running sentry mode 24 X 7 than you did driving those 500 miles.

Without using sentry model your car will likely "use" 2-3 miles a day worth electricity sitting there, rather than 24-48 miles of electricity sitting there. The choice you have to make is, do you care that it will cost you that much to run sentry mode? Some do, and some dont, but the car was not designed with it in mind, and it was bolted on later.

Sentry mode doesnt let the car sleep, so the car will use a lot more electricity, as you are finding out.
 

JindoFuzz

Member
Feb 26, 2021
92
92
Portland, OR
Unless you have some extremely high different rates, 175kwh should cost you around $7 on PortlandGeneral's time-of-use overnight rate(0.04/kwh) or $10 on the 0.063/kwh residential-anytime rate.
I’m not on time-of-use yet, but I am on the green power plan, so I’m just south of $.10/kWh. I plan to swap to time of use as soon as my L2 charger is set up.
 

mrau

Authorized Driver
Nov 12, 2018
411
791
Mid-Michigan
In the Sentry Mode settings you can automatically exclude your home location. That way Sentry will always be on when you are not parked at home. Many folks use this setting so the car can sleep when you do.

Also, you will really appreciate L2 charging when you get it. Makes EV life so much more fun.
 

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