# Can you help me do math?

edited November -1 in Model 3
Because I'm an idiot.

My question is this - how much am I spending preconditioning the car (warming the cabin) to ~72F for 1 hour? Just a best guess is all I'm asking.
~40F in my garage.
Here's how much I pay per my Xcel Energy statement (MN)

Electric/kWh per Day 70.2
Electric/Cost per Day \$9.58

I'm just curious how much warming the battery is costing me every day (ROUGHLY).

TIA

• edited November 2019
Not much
• edited November -1
For 1 hour?

≤ 6kWh
• edited November 2019
what is that in \$?
• edited November -1
And you're paying roughly 13.6 cents per kWh, so ~\$0.8188/day.
• edited November 2019
Sorry less than or equal to 81 cents per day.
• edited November -1
GTFOH! Sweet. There goes that worry.
• edited November 2019
and THANK YOU
• edited November -1
shit, I might as well prewarm for 2 hours. 2 bucks.
• edited November 2019
For future reference, you listed kWh and \$ usage per day

So \$9.58 / 70.2kWh = \$0.136/kWh

Cabin heater is a 6kW heater running for 1 hour so thats a maximum of 6kWh you could use.

\$0.136 x 6kWh = \$0.818
• edited November -1
Ya its only \$2. But its \$60 every month. or \$720 per year for a preheated cabin.
• edited November 2019
Gotcha.
Strange my statements don't say/show the \$0.136/kWh. Why make me do math....
• edited November 2019
Thats why there are forums. You're welcome.
• edited November 2019
Agreed. It can add up. But in my mind for some odd reason I was ready to hear \$5/day for an hour of cabin warming. So less than \$1 was awesome to find out.
I'll never really prewarm for 2 hours...Just was happy how little it did cost for 1 hour.
• edited November 2019
Cost depends on your electric pricing. For me it's about \$0.10/kWhr, so 6 kWhr is about \$0.60.

Next question is why are you running it for an hour? The cabin should warm up within about 5 minutes. If you use the new "finish by" charging strategy you can use your charging to warm the battery. I'm not Minnesota cold (garage is usually in the 50's on cold mornings), but even if it finishes charging close to an hour before I leave I generally don't have any regen dots when I leave. Now if I can just get the timing a bit better I'll be all set. I put in finish by 7:30 & it has been done between 6:20 and 7:00 every day so far. I don't care if it goes all the way to my set point, so I'll probably move the finish line to a bit later to be sure it is pretty warm when I leave.
• edited November 2019
No worries. After yesterdays 15 degree temperatures, leaving work i definitely can see the benefit of preheating my cabin for even just 5 minutes.
• edited November 2019
And it wouldn't be for a full year. Probably ~5 months. So \$300/year.

but I love regen that much
• edited November 2019
@Effopec

If I do nothing I have 0 regen (all dots) when I start driving.
If I prewarm + charge for 1 hour before leaving I get about half or more regen back (~50% or less dots). For less than \$1/day I'll take that improvement.
• edited November 2019
***I should mention this is after the car sits all night in the freezing cold. Taken from someone else on here a 'cold soaked battery'
• edited November 2019
Even this week when it was 12 degrees in the morning my garage was about 55 degrees. So i can imagine i shouldnt have a horrible time with cold battery packs.
• edited November -1
And really -- while that's the max on the heater, my TeslaFi preconditioning losses are *significantly* less than that for 30 minutes to an hour (usually .1 kwh, though there was one morning it was 1.1kwh used), so you'd be looking at closer to 30 cents/hour "real world".
• edited November 2019
garage insulated to some degree? I am planning on doing mine just to help my car
• edited November 2019
@hokie

Back to 2 hours of prewarm for 60 cents!
• edited November -1
Ya definitely to some degree. There are typical cinder blocks up to i think 2'-6", but from there its insulated drywall. Garage is also underneath the house, raised ranch style, and there are ducts that run into the garage despite that i have the vents closed. Even better my main panel is directly next to where i park so a charger installation will be a breeze.
• edited November -1
I'll take the 2 hours for 60 cents plz
• edited November 2019
With our 1.5 cents/kwh TOU plan here, it's well worth it to me.