Adding 6-20 or 14-50 to a 100 amp service

[Hoxlox]

I have an order in for a MYLR which should come in in two weeks. I've just begun thinking about how to charge the car once it gets home and am thinking of putting in either a 6-20 or a 14-50 plug in my garage. I have some requests out for quotes with electricians but I wanted to check with folks here on their experience installing either of these two outlets on a 100 amp service. I don't want to invest the money to upgrade my service to 200 amp just yet. Here are some of the details of the house:

• We currently have 100 amp service in a 1800sq ft home with a panel and sub panel which has space for additional breakers
• We use LED lighting throughout the house
• Some appliances are gas -water heater & stove
• We have an oil furnace for home heating
• Other high energy equipment are an electric dryer, freezer and a Mitsubishi mini split/heat pump system
  • The mini split is on a 40 amp breaker and the sticker on the unit says the minimum ampacity is 29.9 amps

As I'm getting quotes from electricians in my area, would love any inputs on whether or not it would be possible to add a 6-20 to my current service or whether I would absolutely have to upgrade my service for this. TIA!

 

[jcanoe]

For home charging you should consider how many miles you commute weekdays and drive on the weekend. A 240V/20 amp circuit for EV charging can charge the Tesla Model Y at up to 14 miles of driving range added per hour while charging. This is equivalent to adding 5% to the battery per hour (A full charge at this rate would take ~20 hours but you would probably never be charging from ~0% to 100%, more likely 20% to 80%.

It would take 12 hours to add 60% to the battery and that might be OK. Assuming you can take advantage of an off-peak utility rate, perhaps between midnight and 0600 that is a 30% charge over a 6 hour off-peak window, approximately 80 miles of range added.

If you are able to add a 240V/40 amp circuit to your existing panel then every number above would be doubled (28 miles of range added per hour, while adding 10% to the battery per hour. A full charge would take ~10 hours and you could add 60% charge to the battery during the period between midnight and 0600 (assuming this is an off-peak rate window.)

If your electrical service panel is more than 30 years old you may want to have it replaced. Panels do wear out over time and you could consider upgrading to at least 150 amp if not 200 amp service at the same time.

You should skip the idea of a installing a receptacle and install the Tesla Wall Connector (hard wired, no receptacle used.) The Wall Connector can be provisioned for use on any 240V circuit from 15 amps up to 60 amps including: 15/20/30/40/50/60. Plenty of Tesla users have installed the Wall Connector with 30 amp circuits.

 

[MattM24]

For home charging you should consider how many miles you commute weekdays and drive on the weekend. A 240V/20 amp circuit for EV charging can charge the Tesla Model Y at up to 14 miles of driving range added per hour while charging. This is equivalent to adding 5% to the battery per hour (A full charge at this rate would take ~20 hours but you would probably never be charging from ~0% to 100%, more likely 20% to 80%.

It would take 12 hours to add 60% to the battery and that might be OK. Assuming you can take advantage of an off-peak utility rate, perhaps between midnight and 0600 that is a 30% charge over a 6 hour off-peak window, approximately 80 miles of range added.

If you are able to add a 240V/40 amp circuit to your existing panel then every number above would be doubled (28 miles of range added per hour, while adding 10% to the battery per hour. A full charge would take ~10 hours and you could add 60% charge to the battery during the period between midnight and 0600 (assuming this is an off-peak rate window.)

If your electrical service panel is more than 30 years old you may want to have it replaced. Panels do wear out over time and you could consider upgrading to at least 150 amp if not 200 amp service at the same time.

You should skip the idea of an installing a receptacle and install the Tesla Wall Connector (hard wired, no receptacle used.) The Wall Connector can be provisioned for use on any 240V circuit from 15 amps up to 60 amps including: 15/20/30/40/50/60. Plenty of Tesla users have installed the Wall Connector with 30 amp circuits.

I agree with the old panel and service in general comment.
My opinion if 200A, don’t go any smaller.

Your Electricians will let you know what your specific options are.

You’ll only get opinions here, of which mine are for you to get a Tesla Wall Connector and wire for full capacity and set to whatever you can safely.
When you do get a 200A panel, crank it to full capacity at that time.

@jcanoe is right about what you need, but I like to have full capacity for when other people come over for a short period of time and need a charge.

 

[H-H-H]

I agree with what others have said. My situation was very similar to what you describe, including a sub panel in the garage, AC unit, and electric dryer and oven, and gas stove. I have 125A service and upgrading would have been cost prohibitive due to underground service - upgrading would have required digging a trench. I don’t have solar or battery storage.

There were a couple options at the time (2019). One was to install a gadget, from DCC Electric, to monitor the panel and pause charging during high use but setting to a higher amperage (50A circuit, charging at 40A), another was to set to a lower amperage. I think that would have added $1k to the cost. I went with setting to 30A (charging at 24A), since that suited my driving needs. Installed the Tesla wall connector because my utility subsidized the install but required a “charger” to be permanently installed (a regular plug didn’t qualify).

Also replaced the panels since they were 40 yr old.

Works fine for daily driving about 30 mi per day. Model 3 mid range, plug in a could times a week.

 

[Cosmacelf]

@jcanoe said it best. If you can live with the charging speeds he outlined, then just do a 20A/240V circuit.

 

[Hoxlox]

For home charging you should consider how many miles you commute weekdays and drive on the weekend. A 240V/20 amp circuit for EV charging can charge the Tesla Model Y at up to 14 miles of driving range added per hour while charging. This is equivalent to adding 5% to the battery per hour (A full charge at this rate would take ~20 hours but you would probably never be charging from ~0% to 100%, more likely 20% to 80%.

It would take 12 hours to add 60% to the battery and that might be OK. Assuming you can take advantage of an off-peak utility rate, perhaps between midnight and 0600 that is a 30% charge over a 6 hour off-peak window, approximately 80 miles of range added.

If you are able to add a 240V/40 amp circuit to your existing panel then every number above would be doubled (28 miles of range added per hour, while adding 10% to the battery per hour. A full charge would take ~10 hours and you could add 60% charge to the battery during the period between midnight and 0600 (assuming this is an off-peak rate window.)

If your electrical service panel is more than 30 years old you may want to have it replaced. Panels do wear out over time and you could consider upgrading to at least 150 amp if not 200 amp service at the same time.

You should skip the idea of a installing a receptacle and install the Tesla Wall Connector (hard wired, no receptacle used.) The Wall Connector can be provisioned for use on any 240V circuit from 15 amps up to 60 amps including: 15/20/30/40/50/60. Plenty of Tesla users have installed the Wall Connector with 30 amp circuits.

Thank you for your response, this all makes sense! I didn't think about not needing a full charge each night. Our daily commute is around 16 miles or so (round trip) and we have an ICE car for longer trips and a supercharger around 5-6 miles from our place for an emergency full charge if needed. I think I'll ask the electrician for a 240V/20 amp as it'll suffice for what we need.

 

[ewoodrick]

I have an order in for a MYLR which should come in in two weeks. I've just begun thinking about how to charge the car once it gets home and am thinking of putting in either a 6-20 or a 14-50 plug in my garage. I have some requests out for quotes with electricians but I wanted to check with folks here on their experience installing either of these two outlets on a 100 amp service. I don't want to invest the money to upgrade my service to 200 amp just yet. Here are some of the details of the house:

• We currently have 100 amp service in a 1800sq ft home with a panel and sub panel which has space for additional breakers
• We use LED lighting throughout the house
• Some appliances are gas -water heater & stove
• We have an oil furnace for home heating
• Other high energy equipment are an electric dryer, freezer and a Mitsubishi mini split/heat pump system
  • The mini split is on a 40 amp breaker and the sticker on the unit says the minimum ampacity is 29.9 amps

As I'm getting quotes from electricians in my area, would love any inputs on whether or not it would be possible to add a 6-20 to my current service or whether I would absolutely have to upgrade my service for this. TIA!

If you have a subpanel already, then you may be up against the limits of the service. Just get as much as you can get.

How much is your commute?

I have two Teslas and we alternate sharing off of a standard 120V 15A plug. That can add 60 miles in 12 hours, which is good enough for most people.

 

[jcanoe]

Thank you for your response, this all makes sense! I didn't think about not needing a full charge each night. Our daily commute is around 16 miles or so (round trip) and we have an ICE car for longer trips and a supercharger around 5-6 miles from our place for an emergency full charge if needed. I think I'll ask the electrician for a 240V/20 amp as it'll suffice for what we need.

Do consider the hard wire option instead of a Receptacle. Install the Tesla Wall Connector on the 240V/20 amp circuit. The Wall Connector install can end up costing the same or slightly less than the 6-20R (does not require a separate GFCI circuit breaker), the charging cord of the Wall Connector is longer (24 feet) than on the Mobile Connector and the Wall Connector is fully rated for outdoor as well as indoor (garage) installation. Other advantages of the Wall Connector include the ability to limit charging to specific VINs and automatic load balancing when 2 to 6 Wall Connectors share a sub panel (although you probably don't the need or have the capacity to charge more than 1 EV at a time.)

 

[Hoxlox]

I agree with what others have said. My situation was very similar to what you describe, including a sub panel in the garage, AC unit, and electric dryer and oven, and gas stove. I have 125A service and upgrading would have been cost prohibitive due to underground service - upgrading would have required digging a trench. I don’t have solar or battery storage.

There were a couple options at the time (2019). One was to install a gadget, from DCC Electric, to monitor the panel and pause charging during high use but setting to a higher amperage (50A circuit, charging at 40A), another was to set to a lower amperage. I think that would have added $1k to the cost. I went with setting to 30A (charging at 24A), since that suited my driving needs. Installed the Tesla wall connector because my utility subsidized the install but required a “charger” to be permanently installed (a regular plug didn’t qualify).

Also replaced the panels since they were 40 yr old.

Works fine for daily driving about 30 mi per day. Model 3 mid range, plug in a could times a week.

This is something I'm struggling with - finding out how old my panels are. I've looked inside and out and there's no installation date on it. I think I'll have to call the company that I think installed it (their sticker is on the panel) and see if they have any records on when it was installed.

 

[Hoxlox]

If you have a subpanel already, then you may be up against the limits of the service. Just get as much as you can get.

How much is your commute?

I have two Teslas and we alternate sharing off of a standard 120V 15A plug. That can add 60 miles in 12 hours, which is good enough for most people.

This makes sense. I might try out doing 120V 15a plug for the first month to see how much of a deficit I end up having/needing to go to the supercharger to top off. Also, given electricity rates in my area, it might sometimes be only marginally cheaper charging at home as compared to Supercharger rates.

 

[Hoxlox]

Do consider the hard wire option instead of a Receptacle. Install the Tesla Wall Connector on the 240V/20 amp circuit. The Wall Connector install can end up costing the same or slightly less than the 6-20R (does not require a separate GFCI circuit breaker), the charging cord of the Wall Connector is longer (24 feet) than on the Mobile Connector and the Wall Connector is fully rated for outdoor as well as indoor (garage) installation. Other advantages of the Wall Connector include the ability to limit charging to specific VINs and automatic load balancing when 2 to 6 Wall Connectors share a sub panel (although you probably don't the need or have the capacity to charge more than 1 EV at a time.)

I really did want a wall connector, but we might end up moving to a new house/building a house in 3-4 years so I'm struggling with the concept of adding something that I can't take with me when I move.

 

[jcanoe]

This makes sense. I might try out doing 120V 15a plug for the first month to see how much of a deficit I end up having/needing to go to the supercharger to top off. Also, given electricity rates in my area, it might sometimes be only marginally cheaper charging at home as compared to Supercharger rates.

Level 1 charging (120V/15 amp) effectively adds ~4 miles of range per hour while charging. If you drive ~30 miles per day or less it may be all that you need. 120V charging is ~80% efficient, while 240V charging has been shown to be as much as 95% efficient. You would be throwing away 15% of the electricity used to charge at 120V versus 240V every time you charge. MA has some of the highest electric utility rates in the north east if not the lower 48 states.

 

[jcanoe]

I really did want a wall connector, but we might end up moving to a new house/building a house in 3-4 years so I'm struggling with the concept of adding something that I can't take with me when I move.

The Wall Connector can be disconnected by an Electrician in under 30 minutes when it is time to move so you can take it with you.

 

[Hoxlox]

Level 1 charging (120V/15 amp) effectively adds ~4 miles of range per hour while charging. If you drive ~30 miles per day or less it may be all that you need. 120V charging is ~80% efficient, while 240V charging has been shown to be as much as 95% efficient. You would be throwing away 15% of the electricity used to charge at 120V versus 240V every time you charge. MA has some of the highest electric utility rates in the north east if not the lower 48 states.

Interesting thought. I didn't think of efficiency either. Would the electrician just cap off the connection when I take the wall charger out? Also, since you've had your Tesla for a while, does it make sense to then order the mobile charger if I'm already getting a wall charger? Have you ever had to use it on the road?

 

[ewoodrick]

Level 1 charging (120V/15 amp) effectively adds ~4 miles of range per hour while charging. If you drive ~30 miles per day or less it may be all that you need. 120V charging is ~80% efficient, while 240V charging has been shown to be as much as 95% efficient. You would be throwing away 15% of the electricity used to charge at 120V versus 240V every time you charge. MA has some of the highest electric utility rates in the north east if not the lower 48 states.

In a Model 3 and Model Y, while the chart indicates 4 mph, it is actually 5, after the car sleeps. Been there, done that for over 2 years.

It takes a lot of "efficiency" to add up to the possible cost installing higher speed charging.

I just looked at some of the Boston power rates, they were showing well less than $0.20 which is quite reasonable.

In 10 full charges of the battery, 3,000 miles, 700kWh, the 15% difference @$0.15/kWh would be $10,50.
90,000 miles, $315.

Is the efficiency really worth worrying about?

 

[Cosmacelf]

Interesting thought. I didn't think of efficiency either. Would the electrician just cap off the connection when I take the wall charger out? Also, since you've had your Tesla for a while, does it make sense to then order the mobile charger if I'm already getting a wall charger? Have you ever had to use it on the road?

I have used my Mobile Connector often enough while on the road. Once I ended up at Big Bear ski area in the winter with like 3 miles of range left and dropping fast (due to cold weather). I had rented a house with a garage though so I could plug it in to a 20A receptacle which saved my bacon. Basically, if you can figure out destination charging, you can usually avoid one Supercharger stop on the way back. So usually not 100% needed if the SC network is well built out in your travel area, but a nice convenience.

And removing a Wall Connector really is a DIY job. Just flip off the breaker and have at it. Yes, just wire nut the wires and screw on a $1 plate onto the electrical box. Leave the breaker off and label it for the next homeowner.

As far as efficiency goes, I made this calculator comparing 120V charging vs a 240V/48A charging (not your exact situation). Scroll down page to see: CarCharging.us

 

[jcanoe]

Interesting thought. I didn't think of efficiency either. Would the electrician just cap off the connection when I take the wall charger out? Also, since you've had your Tesla for a while, does it make sense to then order the mobile charger if I'm already getting a wall charger? Have you ever had to use it on the road?

The electrician would cap off the wires and install a cover plate when removing the Wall Connector. You could also sell it with the home for the next owner who might be able to use it. In general electric vehicle service/supply equipment (EVSE), i.e. the Wall Connector and Mobile Connector are both examples of EVSE, come with a 3 year warranty and will eventually need to be replaced depending on age, wear and tear and usage.

My 2020 Long Range Model Y came with the Mobile Connector w/5-15 plug adapter. Except to test this EVSE I have never needed to use it. On road trips I use the Tesla Supercharger network. I also carry the Tesla SAE J1772 charging adapter (one comes with every new Tesla vehicle.) The J1772 adapter is useful when traveling because it enables you to use any public Level 2 charging station you may encounter at a shopping center, parking garage or hotel. Some public Level 2 charging station are free to use (while parking, for a few hours.) Download the Plugshare app to locate available charging stations where you live or while traveling. Also, Google Maps can display EV Charging Stations as well as Tesla Supercharger stations.

The Tesla Mobile Connector can be useful while traveling if you stay with family, etc. or while camping. You can purchase different power plug adapters for the Mobile Connector depending on your need. Some Tesla owners find use for the Mobile Connector while traveling and many other Tesla owners have not had the need to use it while at home or while traveling (they have found other ways to charge.)

I suggest holding off on purchasing the Mobile Connector kit unless you know where and how you would use it when charging your Tesla Model Y. I would put the $230 cost of the Tesla Mobile Connector kit towards the purchase of the Tesla Wall Connector ($475). (The total cost of purchasing, installing the Wall Connector can end up costing about the same amount as the total cost of adding a circuit with a receptacle and purchasing the Mobile Connector because you won't need to install a GFCI circuit breaker or a receptacle, also purchase a cable organizer to mount the Mobile Connector and hang up the charging cord.)

 

[Big Dog]

I have 100 amp service and the electrician was able to add a sub-panel for the Tesla charger. Might ask your electrician if a sub-panel is an option.

 

[jcanoe]

I have 100 amp service and the electrician was able to add a sub-panel for the Tesla charger. Might ask your electrician if a sub-panel is an option.

A sub panel, by itself, can add space so there is room to install additional circuits, breakers. If the home's electrical service is maxed out then you can't add any additional circuits without also increasing the electrical service coming into the home.

 

[Mike728]

...
There were a couple options at the time (2019). One was to install a gadget, from DCC Electric, to monitor the panel and pause charging during high use but setting to a higher amperage (50A circuit, charging at 40A), another was to set to a lower amperage. I think that would have added $1k to the cost. I went with setting to 30A (charging at 24A), since that suited my driving needs. Installed the Tesla wall connector because my utility subsidized the install but required a “charger” to be permanently installed (a regular plug didn’t qualify).
...

I also have 100A service and a trusted electrician said I need to go 200A if I want to add anything over 20A and pass inspection. I live in a very permit obsessed town. The total cost came in a little over $10k, which is not something we're going to entertain. I called another electrician that's scheduled to give me an estimate next week and told him to cancel for the 200A need. He mentioned that same management device listed above and said it was allowed, so we're keeping the appointment. My question, does anyone reading this have one, or know anything about them? They appear to cost less than $1k, so much more reasonable, but only if they work.