Work From Home Charging

[ewoodrick]

Hey guys, I'm planning to buy a Tesla M3. I work from home and don't drive much, just errands here and there. I plan to charge using 110v since I work from home and leave the car plugged in all day until I have to go somewhere.

Would my power bill increase a lot leaving the car plugged in all day? I've read that Tesla recommends keeping the car plugged in even after the car is fully charged. I'm also wondering if I could unplug the car when it's fully charged to save some money. If I leave the car plugged in, it might end up costing more than if I kept my gas vehicle. Thanks.

I have two Teslas that alternate charging on a single 120V@15A circuit,

It fits our needs with a lot of time that nothing needs charging.

Power bill change isn't going to be noticeable if you leave it plugged in. Honestly, you may not even be able to see a change in your bill for charging.

 

[m3fan2023]

Welcome to the Tesla family @m3fan2023 ! I would recommend having 220v charging available at home (not sure if you said you planned on having it installed or not) but there is no harm nor additional cost with charging at 110v.

I am not sure (please correct me anyone who knows better) but from what I understand at the lower voltage it is actually slightly more efficient while significantly slower. It is also better for the battery!

I had a M3SR+ for a couple years and loved it. It is a great car, plenty of features, and quite comfortable. I discovered that 110v charging was just fine 90% of the time, but there were instances where I really needed to charge at the faster rate as I had more driving to do later in the day.

Of course, now I drive 140 miles a day for work... so the 2019 M3SR+ was just a bit too short of range for me.

Thank you for the welcome! I was hoping to use only 110v because it'll be plugged in all day, but I might eventually get 220v if I start driving more (kind of like your situation).

Wow, that's a lot of miles that you drive a day!

 

[m3fan2023]

If I understand your concern, it's that the car will take more energy if it's kept plugged in and that's not the case. Think more on what will cause battery drain. You didn't mention if the car will be garage kept. This will make a big difference in power use. The car will use more energy to keep the battery and inside of the vehicle cool. Depending on your location, it may have to keep things warm. Keeping sentry on will consume more power as well. The vehicle will go into a sleep mode for most of the time it's not being used which conserves power. Checking the car with the app, sentry mode or if the vehicle has to cool or heat the battery or inside will keep the car from sleeping. Tesla has always recommended keeping the car plugged in, although it's never recommended to keep it fully charged. Objectively hovering the battery pack around 50% will yield better longevity. Of course, this topic creates it's own debates with miles and miles of threads. It's already been recommended to check with your utility company and see if there are off peak plans and such and attempt to save money in that direction. Tesla now has scheduled charging so you can take advantage of lower rates charging during those times. I think you should look into a tesla wall connector anyway and when or if you have one installed, future proof your residence by pre wiring for a second charger. Yes, it happens, there are many including myself that own two and a 3rd tesla is in our future. Also, one other thing. Check with your utility company and tax advisor for there can be rebates and tax incentives for installing a charger.

Best of luck with your purchase. Have fun and hang out here on TMC for many more answers.

Thank you! I forgot to mention, yes, it will be in the garage!

 

[m3fan2023]

Hmm, I always feels EV is better if you drive big miles due to the cheaper fuel and maintenance cost. If I am driving so little, I probably will take this opportunity and buy a special car with poor MPG that has good resale values. Like C8 corvette or Bronco. EV is very good for daily driving though.

I thought the same thing, but I've read that it's hard on gas vehicles when you have short trips because the engine can't really warm up.

 

[m3fan2023]

For now we mostly charge on 110v since on a typical day the car will at the longest see 30 miles a day, but usually much less. We saw almost no bump on our bill, but here we pay $0.10 per kWh.

I also work from home, my wife drives to work twice a week, 15 miles each way.

That's great to hear your bill didn't go up a lot.

 

[m3fan2023]

I have two Teslas that alternate charging on a single 120V@15A circuit,

It fits our needs with a lot of time that nothing needs charging.

Power bill change isn't going to be noticeable if you leave it plugged in. Honestly, you may not even be able to see a change in your bill for charging.

That would be great if my bill didn't go up so much!

 

[m3fan2023]

240v charging is actually more efficient by a tiny amount. Because it doesnt need to run all of the ancillary items for as long.

I bet it would be the difference of a few dollars per month. Not a huge deal in my opinion.

Maybe I'll eventually get 240v.

 

[m3fan2023]

In my experience, 240V charging is actually quite a bit more efficient. My calculations have shown about 87% charging efficiency on 120V vs 95-96% charging efficiency on 240V/48A. Now, that efficiency is power from the vehicle charge inlet vs what actually goes into the battery, so there may some efficiency difference on the source/EVSE side, but I suspect it is insignificant compared to the vehicle side. The difference in battery wear between charging with 120V at 1.2kw vs 240V at 7-11kw is so tiny that it may as well be nonexistent. Even max L2 charging speeds of 48A/11kw is essentially trickle charging for a modern EV and will not generate any noticeable amount of heat in the battery.

I will have to see how 120V charging works for me and maybe get 240V.

 

[m3fan2023]

For charging at home, the key is to set up time of use (TOU) plan with your electric utility - lowering your charging rates at various times of the day. I would think that all utilities offer some variation on this. Obviously, you have to find a plan that gives a beneficial rate for the time of day you plan on charging. Inevitably, most plans will discourage (i.e., charge higher rates) during peak usage times - usually late afternoon, when it's hottest and people are running their a/c. Some plan surely offers a meaningful reducation in the early morning hours.

My TOU plan (with So. Cal. Edison) offers rates that are about one quarter peak rates, but that's for overnight charging (after 9:00 pm to 8:00 am). 8:00 am to 4:00 pm is only a slight increase. But between 4:00 pm and 9:00 pm, the price skyrockets. So long as you don't make it a habit to run heavy appliances between 4 and 9, you'll save a ton.

This is a great idea.

 

[brianbcc]

I will have to see how 120V charging works for me and maybe get 240V.

Same boat as me.

My original plan was to just use 120v overnight charging in garage since we don't drive much, and then see how it goes, as to whether I proceed with upgrading our garage outlet to 240v.

But honestly after two months, I've had no problems with staying on 120v charging.

And on the rare occasion where we actually take a trip, there are plenty of ChargePoint and Tesla chargers for a quick fill-up.

Actually there's a Tesla supercharger across the street from my house lol

 

[ewoodrick]

For charging at home, the key is to set up time of use (TOU) plan with your electric utility - lowering your charging rates at various times of the day. I would think that all utilities offer some variation on this. Obviously, you have to find a plan that gives a beneficial rate for the time of day you plan on charging. Inevitably, most plans will discourage (i.e., charge higher rates) during peak usage times - usually late afternoon, when it's hottest and people are running their a/c. Some plan surely offers a meaningful reducation in the early morning hours.

My TOU plan (with So. Cal. Edison) offers rates that are about one quarter peak rates, but that's for overnight charging (after 9:00 pm to 8:00 am). 8:00 am to 4:00 pm is only a slight increase. But between 4:00 pm and 9:00 pm, the price skyrockets. So long as you don't make it a habit to run heavy appliances between 4 and 9, you'll save a ton.

If you are charging at 120V, a TOU rate is probably the worse thing that you can do.
And even if charging at 240V, TOU rates are far from being obviously great. You are near LA and the TOU rates probable make sense. But in many other parts of the country, the penalty that you pay for the 4-9PM charging can overwhelm the savings that you get other times. That's because, pretty much by definition, 4-9PM is the time of the day that you use the most electricity.

 

[TornadoTJ]

We are in a tiny town of only 1900 residents, but we have a Supercharger station. I think it's because we are just to the west of Austin and just to the north of San Antonio, and also because we are a tourist destination. I think we've used the Supercharger twice in 7,000 miles. Both times were because we had been on a road trip and were low enough to make it worthwhile to bring the car up from 10-20% to 80% (even though we have LFPs, I don't like to Supercharge all the way) and because it's right by our grocery store so we just left it there and went to the store. We use the Chargepoint more than the Supercharger, even though we have 2 years of Supercharging for free.

Now that I'm thinking about this, I guess I could turn down the charge rate on the Supercharger so that it doesn't hammer the batteries. The Chargepoints in town are Level 2, so not as bad.

Our M3 is sitting at our house sipping on 12a right now.

 

[Gasaraki]

Hey guys, I'm planning to buy a Tesla M3. I work from home and don't drive much, just errands here and there. I plan to charge using 110v since I work from home and leave the car plugged in all day until I have to go somewhere.

Would my power bill increase a lot leaving the car plugged in all day? I've read that Tesla recommends keeping the car plugged in even after the car is fully charged. I'm also wondering if I could unplug the car when it's fully charged to save some money. If I leave the car plugged in, it might end up costing more than if I kept my gas vehicle. Thanks.

LOL...

It only uses electricity when it's charging. If it's charged, it stops and doesn't keep drawing power from the socket.

My mind is just blown...

 

[RayK]

Now that I'm thinking about this, I guess I could turn down the charge rate on the Supercharger so that it doesn't hammer the batteries. The Chargepoints in town are Level 2, so not as bad.

There is no way to "turn down" the charging rate (amps) on any Supercharger (or other DCFC) that I know of. L2 charging, yes, you can do this.

edit: The only thing you can do to lower Supercharging charge rate is to find/use a 72kW Urban Supercharger, as opposed to a V3 (250kW).

 

[TornadoTJ]

Good to know, I didn't know. I never thought to try.

 

[Darmie]

LOL...

It only uses electricity when it's charging. If it's charged, it stops and doesn't keep drawing power from the socket.

My mind is just blown...

Not so fast.

Model 3 Owner's Manual | Tesla

Learn how to charge your vehicle and use scheduled charging features.

www.tesla.com

 

[Park2670]

Not so fast.

View attachment 950229

Model 3 Owner's Manual | Tesla

Learn how to charge your vehicle and use scheduled charging features.

www.tesla.com

You are correct, it will pull when it's not charging. If you are sitting in the car, or preconditioning the car, it will pull from the outlet.

But it wont pull 32 amps forever once the battery is done charging.

 

[DuncanM]

Hey guys, I'm planning to buy a Tesla M3. I work from home and don't drive much, just errands here and there. I plan to charge using 110v since I work from home and leave the car plugged in all day until I have to go somewhere.

Would my power bill increase a lot leaving the car plugged in all day? I've read that Tesla recommends keeping the car plugged in even after the car is fully charged. I'm also wondering if I could unplug the car when it's fully charged to save some money. If I leave the car plugged in, it might end up costing more than if I kept my gas vehicle. Thanks.

If you have 20amp breaker feeding your 120v outlet, you should be able to change the outlet to a NEMA 5-20 and charge at 16amp/120v instead of 12amps, (with the appropriate adapter cable for your EVSE).

The car will draw very minimal amounts of power after it reaches the preset SOC. One advantage of leaving it plugged in is that you can remotely precondition the car and battery via your cellphone app, which will save range after you depart.

 

[K.I.T.T.23]

Thank you for the welcome! I was hoping to use only 110v because it'll be plugged in all day, but I might eventually get 220v if I start driving more (kind of like your situation).

Wow, that's a lot of miles that you drive a day!

yeah... the job is good or I wouldn't. Also, if I didn't have a car that reduced the stress of such a long drive due to Auto Pilot I wouldn't. I also do enjoy driving the car!

As stated by someone later on, the 110v apparently is less efficient than the 220v (uses more KWh to put power into your car) so you may want to seriously consider an outlet.

Either way, good luck!

 

[m3fan2023]

yeah... the job is good or I wouldn't. Also, if I didn't have a car that reduced the stress of such a long drive due to Auto Pilot I wouldn't. I also do enjoy driving the car!

As stated by someone later on, the 110v apparently is less efficient than the 220v (uses more KWh to put power into your car) so you may want to seriously consider an outlet.

Either way, good luck!

Thank you @K.I.T.T.23 !