Charging dilemma

[Grey_MS_Tx]

I just ordered my first Tesla (75D), which should be here in June. I'm trying to get my charging situation squared away, and I'd love some input.

I work at home, so I don't have a regular commute to worry about.

My house has a 125A main breaker, and my electrician determined I have 26A of capacity available. Further, there are no empty slots in my panel for additional breakers (ugh). So, my options come down to the following:

Option 1 - install a 30A circuit to the garage; this will require addition of a new sub-panel, as there are no open slots for new breakers on the existing panel. Total cost for this option will be roughly $1200, including a 14-30 adapter. A downside here is I've spent $1200, and I'd still need to pay almost all of the cost of option 2 to upgrade service any higher - all of the costs for the option 1 subpanel are throwaway in that case. Charge rate would be 26A, around 17 mph.

Option 2 - upgrade service to house to 200A, and install 50A service to the garage. This requires a new panel, along with all of the new requirements to meet code (new meter housing, etc.). This would come to about $2750, and would provide 40A charging.

Option 2a - I think if I go with option 2, I'd probably add a HPWC for an incremental $500, just for the convenience. I'd presumably wire it in at 60A, so I could charge at 48A.

Option 3 - I'm not really considering this - but if I replaced my electric range with gas, that would free up enough capacity to run 50A to the garage with no further upgrades. Cost here about $800 plus buying a new range, plus buying other new kitchen appliances to match the shiny new range, plus new granite countertops...ha. Clearly an expensive way to go.

Any thoughts?

I would consider going for 110v charging. Yes it is very slow, but if you are working form home the car should be stationary for most of the time where 110 should work fine.
I am on my second MS now, and for the first one I got the dual charger 80A option I also installed the 80A charger at home. To be honest quite a lot of wasted money....
For my new MS I did not get the fast charge upgrade. 48A is more than enough for my use. I drive around 15k miles per year. I think I could make 110v work for me and I know other owners using 110V at home.

Save the money for now and see how you get on with 110 and go from there.

 

[mknox]

Option 3 - I'm not really considering this - but if I replaced my electric range with gas, that would free up enough capacity to run 50A to the garage with no further upgrades. Cost here about $800 plus buying a new range, plus buying other new kitchen appliances to match the shiny new range, plus new granite countertops...ha. Clearly an expensive way to go

I did something similar. When I moved to my current home (1963 build with 100 amp main panel) I brought my almost brand new gas range from my old house with me. It sat in my basement for many years, but when I bought my Tesla, I decided it was time to toss out the old electric and install the gas range. At the same time, my old electric dryer gave up the ghost and so I replaced that with a new gas one. I still have electric hot water, but that will be trickier to replace. The stove and the dryer gave me the capacity I needed for EV charging.

 

[timvracer]

definitely option 2 or 3. We used the 50amp breaker that used to power our range (house built in 1951), and repurposed it for the Tesla charger port. We indeed switched to a gas range sometime back during a remodel.

Invest now, if you are putting out the $$ for this car, it is worth it to get an adequate charging solution. Not sure the HPWC is worth it though, to make it work to it's potential, you'd need a 100A circuit.

 

[GJ79]

I just ordered my first Tesla (75D), which should be here in June. I'm trying to get my charging situation squared away, and I'd love some input.

I work at home, so I don't have a regular commute to worry about.

My house has a 125A main breaker, and my electrician determined I have 26A of capacity available. Further, there are no empty slots in my panel for additional breakers (ugh). So, my options come down to the following:

Option 1 - install a 30A circuit to the garage; this will require addition of a new sub-panel, as there are no open slots for new breakers on the existing panel. Total cost for this option will be roughly $1200, including a 14-30 adapter. A downside here is I've spent $1200, and I'd still need to pay almost all of the cost of option 2 to upgrade service any higher - all of the costs for the option 1 subpanel are throwaway in that case. Charge rate would be 26A, around 17 mph.

Option 2 - upgrade service to house to 200A, and install 50A service to the garage. This requires a new panel, along with all of the new requirements to meet code (new meter housing, etc.). This would come to about $2750, and would provide 40A charging.

Option 2a - I think if I go with option 2, I'd probably add a HPWC for an incremental $500, just for the convenience. I'd presumably wire it in at 60A, so I could charge at 48A.

Option 3 - I'm not really considering this - but if I replaced my electric range with gas, that would free up enough capacity to run 50A to the garage with no further upgrades. Cost here about $800 plus buying a new range, plus buying other new kitchen appliances to match the shiny new range, plus new granite countertops...ha. Clearly an expensive way to go.

Any thoughts?

Although I have a Nema 14/50 available I always charge at 25 amps and it's plenty to charge overnight and my daily commute is about 120 miles. I dial it down to 25 amps to keep the heat down in the charger and the mobile adapter which I believe will let the charger live longer although it's slightly more inefficient. You will be perfectly fine with your 30 amp charging outlet.

 

[Rocky_H]

Hey, @gr2020 , my situation was very similar to yours. I also have a 125A circuit, and my house was built in 1996. It is gas for furnace and hot water heater, so that takes some of the load off, but it has electric for the range, clothes dryer, and air conditioning. But it's a 1600 square foot house, so the air conditioning unit is fairly small--20 or 30 amp circuit I think.

So when the electrician said 26A available, how was that actually phrased? If that is 26 amps of rated circuit, that would mean no 30 amp circuit. You could only add a 20 or 25 amp. In your situation, though, that would still be totally fine with the small amount of miles. Regarding that load calculation, you might want to check if he did the load calc taking into consideration the "non-coincident load" factor that is allowed in the NEC. If you are planning for the car to charge at night, while you would not be using your oven, they do not both have to be added together into your panel's capacity. You can use either, whichever is bigger, for the load calc. Or the same could be done with your electric dryer circuit versus the car.

I would not mess with 120V charging. It's inefficient and really really slow. You can double the charge rate on the same amps by getting the voltage to 240V with a dedicated circuit anyway. Go ahead and check on twin breakers (combining 120V circuits) or nested breakers (combining two pole 240V circuits) to maybe free up physical space in your panel without having to add a sub panel. I have a fairly modern Square D panel, but both of those special types required a split bus bar, which my model of panel does not have. I was only half a space short, so there was a 120V circuit that only went to one outlet that we rarely used, so I was able to give that up to get me space to do a 50A circuit.

I think most of the time, the 30A it would be fine. I'm just worried about those occasions when I need to come home after say 100 mi, then pop out a few hours later for another 100, and maybe it's on a cold day/night so I have less range... Although I'll be the first to admit I'm making up scenarios here that do happen, but not often.

No no no. Don't fake yourself out with these kinds of rationalizations for spending hundreds or thousands of extra dollars for unneeded faster home charging. You are only 5 miles away from the Lone Tree Supercharger, which is about 10X as fast as what you have at home anyway. So if/when that situation comes up, go over and spend 20 minutes to take care of that rare occurrence.

 

[gr2020]

Thanks everyone for your help! I think what I'm going to do is replace either my dryer or range with a gas version, which will free up electrical capacity, and then install a 14-50 in the garage for the car. I thought I wanted a HPWC based on the physical location in the garage needing the 24' cable, but now I have a different location in mind that is closer and I think will work fine with the 14-50 and the regular mobile cable.

While this will still come out at least $2000, at least I'll have a shiny new appliance to show for it! Ha.

 

[Boatguy]

Your electrician seems confused about capacity versus usage. You certainly need panel space for a new circuit for the charger, no escaping that. So you have a pretty simple trade off between a larger main panel and adding a sub-panel.

But it's normal for the sum of the circuits on a panel to be far more than the service to the panel. I have a 200a service and my main panel has 320a of circuits. Look deeper and there is a sub-panel with 125a of service with 560a of circuits.

And this is new construction within the last 18 months, all code compliant.

The discussion of dryers and ovens is irrelevant because all that matters is the current you're drawing at a point in time. If you are charging between midnight and 6am, it's likely that the other consumers in your house (oven, dryer, hair dryer, lights, computers, etc.) are off and your total consumption is very low, less than 20a total. You have plenty of capacity to deliver 48a to your HPWC.

Sure, if you decide to charge the car, bake a cake, dry your clothes, use a hair dryer and turn on every light in the house, you could trip the main breaker. But add up the actual consumption, not circuit size, of those consumers, and you might be surprised. For example, an electric dryer on a 30a circuit that consumes 3.5kW, is only pulling 16a at 220v, more like 15a at a more common 240v. An electric over is even less.

 

[gr2020]

Your electrician seems confused about capacity versus usage.

Well, I don't think he's confused, as I've gotten a similar story from multiple electricians. Adding up the breaker capacity in my box is certainly far over 125A, so you run some calculations to come up with a number to meet the code requirements. Promising not to run the dryer while charging the car apparently isn't sufficient to satisfy the inspectors.

But just to check for myself, I did a little research, and I was looking at this form, which is evidently used to cover article 220 of the NEC:

http://www.douglas.co.us/documents/single-family-dwelling-service-entrance-standard-calculations.pdf

If he said I had 26A available, I'm guessing his total from that form was 99A. To make sure I was in the same ballpark, I ran through the form myself, and my number was even higher.

 

[Boatguy]

Well, I don't think he's confused, as I've gotten a similar story from multiple electricians. Adding up the breaker capacity in my box is certainly far over 125A, so you run some calculations to come up with a number to meet the code requirements. Promising not to run the dryer while charging the car apparently isn't sufficient to satisfy the inspectors.

But just to check for myself, I did a little research, and I was looking at this form, which is evidently used to cover article 220 of the NEC:

http://www.douglas.co.us/documents/single-family-dwelling-service-entrance-standard-calculations.pdf

If he said I had 26A available, I'm guessing his total from that form was 99A. To make sure I was in the same ballpark, I ran through the form myself, and my number was even higher.

OK, I see where he gets the 26a. That's a very onerous form that basically assumes everything is running all the time which goes far beyond the national code. Since you'll have to get a new service, I suggest going for at least 200a since they will require 72a just for two cars. I have two EVs and you're going to like your Tesla. Getting a second EV in the next five years is a reasonable assumption.

You won't like trying to charge your Tesla on 110v. I did that for a year with a BMW i3 and got by because we only drive about 8,000/yr with that car, it uses less power than an a Tesla (about 240Wh/mi), and being retired means I was usually home by later afternoon and didn't depart before 8:30am.

So like another poster wrote, it's like getting a baby, it needs some infrastructure. Enjoy your new car!

 

[TR5642]

Go for the upgrade and install the HPWC. Compared to the cost of the car it isn't that crazy. Particularly the delta between the options. Why?

• Simplicity: With the 20something A charge you will probably be fine but you'll always have to pay attention to keeping things full
• Operational cost: If you've got time of day metering, making sure you can get enough charge in the cheap hours. (here in northern CA, it's 11c kWH overnight and 33c daytime for example)
• Having the HPWC always just hanging there means you won't leave your UMC there when you need it somewhere else. (not to mention having a backup)
• If the car charger is going to push your panel to the limit, something else will make you upgrade service sooner or later anyway.
• Tip: Since you will have capacity on the panel, have the electrician pull another circuit for a 14-50. Consider it efficient future proofing and backup (not to mention potentially friendly if you have a guest)

One POTENTIAL argument to going cheap is if you have a SuperCharger nearby that isn't always full. That would be your backup plan for needing quick charging once in a while.

 

[mknox]

Not sure the HPWC is worth it though, to make it work to it's potential, you'd need a 100A circuit.

I started out using my UMC but had a couple go bad over the years. I'm not sure it's as robust as the HPWC is. I was going to buy a second UMC so I could leave one at home and keep the other in the car, but the incremental extra cost for the HPWC was something like $100 if I recall, so I decided to go that route. I have mine set for 40 amps delivered (to match the capacity of my wiring for the NEMA 14-50) and it provides a nice neat installation in my garage.

 

[Lasttoy]

Ask electrician to put 2 bedrooms on same breaker. That leaves room for double, installation a 40 amp breaker, and 14.50 receptacle in garage. Cheap , easy, all you need, you want 80 amp. But not cost effective if you work from home. ROI is 10 years.

 

[Trocken]

I just ordered my first Tesla (75D), which should be here in June. I'm trying to get my charging situation squared away, and I'd love some input.

I work at home, so I don't have a regular commute to worry about.

My house has a 125A main breaker, and my electrician determined I have 26A of capacity available. Further, there are no empty slots in my panel for additional breakers (ugh). So, my options come down to the following:

Option 1 - install a 30A circuit to the garage; this will require addition of a new sub-panel, as there are no open slots for new breakers on the existing panel. Total cost for this option will be roughly $1200, including a 14-30 adapter. A downside here is I've spent $1200, and I'd still need to pay almost all of the cost of option 2 to upgrade service any higher - all of the costs for the option 1 subpanel are throwaway in that case. Charge rate would be 26A, around 17 mph.

Option 2 - upgrade service to house to 200A, and install 50A service to the garage. This requires a new panel, along with all of the new requirements to meet code (new meter housing, etc.). This would come to about $2750, and would provide 40A charging.

Option 2a - I think if I go with option 2, I'd probably add a HPWC for an incremental $500, just for the convenience. I'd presumably wire it in at 60A, so I could charge at 48A.

Option 3 - I'm not really considering this - but if I replaced my electric range with gas, that would free up enough capacity to run 50A to the garage with no further upgrades. Cost here about $800 plus buying a new range, plus buying other new kitchen appliances to match the shiny new range, plus new granite countertops...ha. Clearly an expensive way to go.

Any thoughts?

Do you have an electric clothes dryer and hot water heater?
Makes a difference