40A Clean Install vs. 80/100A Conduit Install?

[dss33]

We had our house pre-wired for the car charger and they installed 40A (it's the highest they would go, for some odd reason). The wiring is already behind the wall, so it's nice and clean. Though the garage walls aren't finished now, we do plan to finish the garage sometime in the next year or two.

We have the HPWC in hand. It's $400 to install the wall connector on the existing 40A wiring and I think we're OK with the 23 mph charging. That said, we have the option to upgrade to 80A or 100A wiring via a conduit (mounted along the wall/ceiling) for another $350.

1) With the 48A charger in the car, what's the max amperage we'd want to get that's actually going to be useful? 60A?

2) Is it worth it to upgrade the wiring and breaker and have that external conduit, or, given that we don't have a daily commute, should we just stick with the existing 40A line?

Our S (arriving next week!) has the standard 48A charger onboard. We don't drive a ton regularly, though we will take short road trips over the weekend one or two times a month, FWIW.

Thanks in advance for your opinions and experience!

 

[Max*]

23mph charging = full battery in less than 12 hours.

I think only you can answer the question if that's "fast enough".

 

[Rockster]

I'm generally in favor of building out the most robust infrastructure as is reasonably possible when the occasion presents itself. You never know what the future holds. If you add a 100 amp line now, you pave the way for daisy chaining a second HPWC on the same circuit and charging a second Tesla serially. Considering a relatively modest increase in price to upgrade before the garage is finished, it seems worthwhile to future proof your garage with greater charging capacity.

 

[mikeash]

32A will get you a full charge overnight, and I think for most people that's enough. I charge at 40A at home, but I'd be fine with 30A or even 20A.

With a 48A charger in the car, you'd need a 60A circuit to take full advantage of it, as you guessed. Anything beyond that won't increase your charging rate, unless you upgrade to 72A charging in the car (which could then benefit from up to a 90A circuit).

I'm a bit surprised that it costs $400 on existing wiring. It's not that hard to do. I'd have thought it would be less, but maybe I'm being clueless, it has happened before.

 

[dss33]

32A will get you a full charge overnight, and I think for most people that's enough. I charge at 40A at home, but I'd be fine with 30A or even 20A.

With a 48A charger in the car, you'd need a 60A circuit to take full advantage of it, as you guessed. Anything beyond that won't increase your charging rate, unless you upgrade to 72A charging in the car (which could then benefit from up to a 90A circuit).

I'm a bit surprised that it costs $400 on existing wiring. It's not that hard to do. I'd have thought it would be less, but maybe I'm being clueless, it has happened before.

That's good perspective, thank you. I've done a small amount of electrical work before, so I did consider doing the install myself. Though with permitting and electrical code, not to mention the fact that it's an almost $100k car, I figured it was worth spending a little to ensure it's done right. To boot, the builders originally installed a 30A breaker and upgraded to the promised 40A breaker, though I have suspicions that they didn't replace the wire too, so it might actually not be ideal/safe as-is with what I think is 10 gauge. Maybe I'm being overly cautious, but given all of that, I was happy to pay the $400 for peace of mind. It's less than Best Buy (not my first choice) wanted to mount my TV (tile, above fireplace) and run a few wires through smurf tube, so it's a relatively great deal.

 

[AndreSF]

I'm also wondering what "they" will do for $400... Install and wire wall connector? Seems way too much IMO.
On your original question: I would not change anything, unless you are thinking second EV in the near future.

Good luck!

 

[MorrisonHiker]

the builders originally installed a 30A breaker and upgraded to the promised 40A breaker,

Hmm. Hopefully you meant 50 amp breaker for the 14-50 outlet. If it's only 40 amps then I would consider swapping out the wiring and the breaker.

I had two 14-50 outlets installed last year. Had I known about the new 48 amp chargers and new linked HPWCs which came out in April of 2016, I would've had them put in 60 amp breakers and associated wiring instead. Once a second or third Tesla is added to the garage, I'll probably research the 60 amp route as that would allow me to plug in each vehicle and let the HPWCs handle the load balancing.

BTW, depending on your tax situation, you might be able to get 30% back on any upgrades you do for your EV charging when filing your taxes.

 

[Chaz]

We had our house pre-wired for the car charger and they installed 40A (it's the highest they would go, for some odd reason). The wiring is already behind the wall, so it's nice and clean. Though the garage walls aren't finished now, we do plan to finish the garage sometime in the next year or two.

We have the HPWC in hand. It's $400 to install the wall connector on the existing 40A wiring and I think we're OK with the 23 mph charging. That said, we have the option to upgrade to 80A or 100A wiring via a conduit (mounted along the wall/ceiling) for another $350.

1) With the 48A charger in the car, what's the max amperage we'd want to get that's actually going to be useful? 60A?

2) Is it worth it to upgrade the wiring and breaker and have that external conduit, or, given that we don't have a daily commute, should we just stick with the existing 40A line?

Our S (arriving next week!) has the standard 48A charger onboard. We don't drive a ton regularly, though we will take short road trips over the weekend one or two times a month, FWIW.

Thanks in advance for your opinions and experience!

I have the same philosophy as Rockster. If I'm going to spend the money, I try to future-proof any install. Like Max* said, only you can answer that question.

In my opinion, I would add the 100A line preferably in the wall (perhaps up the wall, through the space above the garage, and back down) since you haven't finished the garage yet. And maybe use the already existing 40A as a back-up outlet, just in case your HPWC ever fails.

I had a 100A circuit added in my finished garage for my WC (had to upgrade to a larger panel), and before the the drywaller came out, I installed an additional NEMA14-50 as a back-up.

Good luck!

 

[jbcarioca]

I have 23A, which is fine for day-to-day use, for me. Unless you will regularly need >150 miles/day and leave earty-arrive late, your existing infrastructure should do fine. I agree with others that, other things being equal, more is better. I'd rather have DC fast at home. Other things are not equal, though, so cost-effectiveness rules for me. I have actually never needed faster charging. I always have enough overnight to travel >175 miles while having more reserve than I need. For sure YMMV.

 

[DoubleDownOn9]

Definitely do 80A/100A. The best reasons I can think of are:

1) Getting home late from a long drive and still needing to go to work the next day. This happened to me as I got in from LA at 4am one night and needed to go to work the next day at 7 (I know, not ideal but it did happen). Every minute counts and I didn't want to sit at a supercharger for 30 minutes when every minute of sleep counted.

2) Who knows what else Tesla will be cooking up in the next 20 years (think hover Tesla). I'm guessing that amps are going to be required in order for it to work.

3) If you catch the EV bug like we did then you'll end up having multiple EVs. If you play musical charger it would be nice to not get up in the middle of the night to switch. Or if you don't want to play musical charger having extra amps in your garage is always good for adding a second charger.

4) If the whole EV thing doesn't work out you can use the 100 amps to build a death star like weapon of some sort.

 

[dss33]

Definitely do 80A/100A. The best reasons I can think of are:

1) Getting home late from a long drive and still needing to go to work the next day. This happened to me as I got in from LA at 4am one night and needed to go to work the next day at 7 (I know, not ideal but it did happen). Every minute counts and I didn't want to sit at a supercharger for 30 minutes when every minute of sleep counted.

2) Who knows what else Tesla will be cooking up in the next 20 years (think hover Tesla). I'm guessing that amps are going to be required in order for it to work.

3) If you catch the EV bug like we did then you'll end up having multiple EVs. If you play musical charger it would be nice to not get up in the middle of the night to switch. Or if you don't want to play musical charger having extra amps in your garage is always good for adding a second charger.

4) If the whole EV thing doesn't work out you can use the 100 amps to build a death star like weapon of some sort.

I hadn't considered the Death Star option. Hmm...that 100 amps is looking mighty tempting now

 

[Macbest]

BTW, depending on your tax situation, you might be able to get 30% back on any upgrades you do for your EV charging when filing your taxes.

Can you explain more? I don't remember seeing the tax impact on install, just on the purchase?

 

[TaoJones]

I'd vote to go big. Better to have it and not need it than the converse.

 

[MorrisonHiker]

Can you explain more? I don't remember seeing the tax impact on install, just on the purchase?

Individuals who purchase and install electric vehicle charging stations may be eligible for a tax credit of 30% of the qualifying costs, up to $1,000. The credit may be applied toward charging stations and required equipment installed between January 1, 2015 and December 31, 2016.

If you have HPWCs installed, need to upgrade your electrical panel, put in 14-50 outlets, etc., then you can possibly get a rebate of 30% off the hardware, wiring, installation, etc. Permitting and inspection fees are not qualifying costs. When I had work done last year, I spent $1844 for a very long run for two outlets in garage, at other side of house from main panel, upgrade subpanel, etc. When I did my taxes this year, I used form 8911 and received over $550 back.

Here are a few links.
Tax Credit for Electric Vehicle Stations - ChargePoint (Click on Home. Notice many states have rebates or tax credits in addition to the federal tax credit.)
Alternative Fuels Data Center
Form 8911, Alternative Fuel Vehicle Refueling Property Credit

Alternatively, you can Google "tax credit for installing electric vehicle charging station" or something similar and see lots of articles describing the tax credit.

Some people have reported they were unable to claim the Alternative Fuel Vehicle Refueling tax credit in the same year that they claimed the $7500 federal tax credit for the vehicle. In my case, I had the electrical work done in 2015 and the car in 2016 so I will claim them on two different tax years.

 

[mikeash]

Note that unlike the vehicle tax credit, the charger tax credit does not work with Alternative Minimum Tax, so if you're lucky enough to be subject to that, you don't get it. I forget exactly how but my accountant managed to claim something like $7 back for me, on a $1150 installation.

 

[FlatSix911]

1) With the 48A charger in the car, what's the max amperage we'd want to get that's actually going to be useful? 60A?
2) Is it worth it to upgrade the wiring and breaker and have that external conduit, or, given that we don't have a daily commute, should we just stick with the existing 40A line?

Our S (arriving next week!) has the standard 48A charger onboard. We don't drive a ton regularly, though we will take short road trips over the weekend one or two times a month, FWIW. Thanks in advance for your opinions and experience!

Based on your use case with a 48A charger in the car and no daily commute, I would recommend the HPWC with the 40A wiring.
You will have a very good overnight charging rate of 23 MPH and can use the Supercharger network on road trips.

Here is a handy chart of charging rates ...

 

[GSP]

I voted for 100 A. But that is just what I would do. I like to be able to top off my car or a guest's quickly if needed. Even if I never will actually need to, it adds peace of mind that I could.

It sounds like 40 A will be fine to cover the OP's driving. If this was all I could install for a reasonable price, I think it would work fine for me as well.

GSP

 

[brkaus]

Remember the $400 doesn't necessarily buy you anything other than some random person coming in, hooking up your HPWC and taking your money. Perhaps someone to blame if things go wrong. If they quoted you $400 to connect to existing wiring that sounds pretty darn high.

Anyway, I don't believe you can put a 50A breaker on 10g wiring so be careful changing out breaker sizes. Did the electrician that quoted you $400 review the breaker and wire size and say it was OK? And what charging current they thought it would support?

Suggest reviewing FlasherZ FAQ as a starting point, if you haven't already read it.

FAQ: Home Tesla charging infrastructure Q&A

 

[Jlwine]

30 AMP can go over 10 AWG wiring
40AMP can go over 8 AWG wiring
50AMP can go over 6 AWG
60-95AMP needs 2 AWG
95-125AMG needs 1 AWG

If they originally wired for 30AMP they may have only used 10AWG!!

 

[dss33]

30 AMP can go over 10 AWG wiring
40AMP can go over 8 AWG wiring
50AMP can go over 6 AWG
60-95AMP needs 2 AWG
95-125AMG needs 1 AWG

If they originally wired for 30AMP they may have only used 10AWG!!

That was my concern too. The second electrician did take a look - I told him safety was a real concern - and he said it checked out. He didn't specify what gauge it was though.

If it were actually 10 gauge on a now 40A breaker, what sort of risks does that potentially entail (to our house and the car)?