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2015 Tesla Model S P85DL -- Electrical Bill higher than expected

VifferFun

Member
Jul 25, 2019
107
117
ON Canada
Hi Everyone!

I purchased a 2015 Model S P85DL in early August and noticed that my electrical bill spiked by a lot more than I was expecting. In my first full billing month since owning the Model S, my off-peak electricity usage (when I charge the car) increased by 700 kWh compared to the same billing month last year (and I wasn't even running my house A/C most of the last month). I just found this surprising, given that:

115,200 = Odometer when purchased in early August:
118,500 kms = Current Odometer
3,000 km = Distance since purchased 1.50 months ago

Of the 3,000 kms, at least 1,000 kms were free supercharging, which means that I charged less than 2,000 kms since purchase at home. This mean that my consumption rate in this billing cycle is at least:

Consumption Rate
= 700 kWh / 2000 kms
= 0.350 kWh / km
= 350 Wh / km

This conservatively-low estimate seems pretty crazy high given that my car's trip computer (which I reset 2200 kms ago) says that I was averaging 211 Wh / km. Nothing else in my home has changed electrically since this month last year. Any ideas? I just downloaded the "Tesla Stats" app on the iPhone and subscribed to a TeslaFi trial to get some more stats to support my investigation. I still LOVE the car!! :D
 

Chaserr

Hyperactive Hyperdrive
Sep 5, 2017
2,666
6,524
Logan
I average higher than 350 wh / mi in my non Ludicrous P85, so you're actually driving very conservatively! The already-conservative EPA rating for your car should be somewhere around 295 wh/m and you're averaging around 220!

Trip computer can't be believed. It's not an overall energy gauge it just shows you what you used while moving and doesn't account for losses at the charger either. TeslaFi will give you a much better view of your car's inner workings!
 
  • Informative
Reactions: Huachipato
Funny you bring this up. When I was at Tesla for service a young guy came in that had just purchased a M3. He was complaining to service that his electric bill was much higher than it should be based on amount of charge to the battery and accounting for modest loss of energy at the charger.

I also talked to another MS owner who stated she was plugging in her car every night to charge to 80%. Her bill was really high so she switched to plugging in every other night.
Now- this shouldn’t have had any impact on the bill because she continued driving the same number of miles, but it did- her bill went down by half.

I think the energy used by the car and charger when plugged in is much higher than we think
 

Galinette

Member
Jan 2, 2018
257
240
Nantes
Hi,

First of all, the charge yield is not 100%. The cars AC DC converter has losses. And charging requires battery thermal management, especially heating when charging cold. Also the battery internal resistance adds losses. I would say you have at least 10% losses and more in cold or hot weather.
Furthermore, your battery looses power (aka vampire drain) without driving. This is typically 1kWh a day.
This may not explain all the difference you observe but clearly reduces it.
 

VifferFun

Member
Jul 25, 2019
107
117
ON Canada
I actually drive very conservatively — I’m certainly not driving like 350 Wh/km. I just completed a 100 km trip right now and TeslaFi says I averaged 157 Wh/km (or 251 Wh/mi). This was a long-distance trip but I suspect my true long-term average is closer to 211 Wh/km (or 338 Wh/mi) as the car trip computer would suggest.

I’m just having difficulty reconciling my home electricity spike with the small amount of electricity expected for my Tesla. I suppose it could be a fluke and something else from my house is cause a huge drain, burn if that was the case I would have expected a similar spike in my non-peak usage as well. Weird! I think TeslaFi and the Tesla Stats app will help me narrow down the electrical usage!

Also, I’ve only had the Tesla Stats app for a few hours but I really like the interface and graphs it provides. It will be really interesting once I have lots of data collected. Seems like it’s a bargain at $28 CAD
 
I actually drive very conservatively — I’m certainly not driving like 350 Wh/km. I just completed a 100 km trip right now and TeslaFi says I averaged 157 Wh/km (or 251 Wh/mi). This was a long-distance trip but I suspect my true long-term average is closer to 211 Wh/km (or 338 Wh/mi) as the car trip computer would suggest.

I’m just having difficulty reconciling my home electricity spike with the small amount of electricity expected for my Tesla. I suppose it could be a fluke and something else from my house is cause a huge drain, burn if that was the case I would have expected a similar spike in my non-peak usage as well. Weird! I think TeslaFi and the Tesla Stats app will help me narrow down the electrical usage!

Also, I’ve only had the Tesla Stats app for a few hours but I really like the interface and graphs it provides. It will be really interesting once I have lots of data collected. Seems like it’s a bargain at $28 CAD

Definitely get Sense!
 

PWlakewood

Active Member
Jan 9, 2019
1,802
1,122
US
Get this device to monitor your electric usage, it's awesome...

The Sense Home Energy Monitor
Have it and love it. Screenshot_20190920-122535_Sense.jpgScreenshot_20190920-122502_Sense.jpg
 

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PWlakewood

Active Member
Jan 9, 2019
1,802
1,122
US
Nice. It's an amazing device! I have sense solar too. Plus monitoring through my Solar inverter (Solar edge).

Off topic but similar theme... Get "Phyn" to monitor water usage. Also decifers what appliance is using water and how much.
Eh, no need to really monitor water as its paid for in our hoa dues. We do conserve water already. I plan on solar one of these days and I will get the sense solar once its needed.
 

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