EV Chargers: How to Choose the Right One for Your Home

EyeOnRivian

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Just watched the latest E for Electric YT video where the host (Alex) had EV industry expert Tom Moloughney go over some of the key factors to consider when selecting a L2 EVSE for your home/garage. I'm sure there are people on this forum that don't have an EV yet or may be upgrading their current EVSE (aka home charger) that just might find this video helpful. Tom provides some good info / tips that I thought was worth passing along here. (Note: video is slightly on the long side at about 40 or so minutes. To save some time I played it back at 1.25 speed and had no problem following along.)


What do you think about Tom's key factors to help determine the proper EVSE for your scenario?

Maybe share some noteworthy info on your EVSE (e.g. charger brand, model details, kW, amps, NEMA rating, amps, UL certified or not, installed in or outside, any charging cable length issues, portable or hardwired, etc.), along with what your primary factors that led you to purchasing/using it (e.g. EV charger kw, battery pack size, smart-charger, price, etc.) and is it meeting your expectations/requirements (e.g. pros, cons, recommend / not recommend, etc.).
 

ajdelange

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I think the most relevant thing here to potential Rivian owners here is that the Rivians are bigger vehicles than even the biggest Tesla (the X), thus use more power and will, thus, take more time to charge with the usual sorts of chargers that the video talks about. We can only do some rough numbers from what we know at this point but the Rivians will have about 400 miles of range from a 180 kW battery. Dividing the watts by the miles we easily see that the Rivians power consumption will be in the neighborhood of 450 Wh/mi under nominal conditions. Throw in winter cold or desert heat and that is going to go up as it will when off road, when driving in rain or snow and in unusually hilly terrain but lets stick with 450 as a sort of nominal everyday use number. The rules for EVSE change if the circuit current is over 60 amps. So lets assume that we install a 60 amp circuit. We must derate that to 48 A (as this is EVSE we're powering). At 240 V 48 A gives us 11.52 kW. That's the advertised size of the Rivian charger. Coincidence? Chargers are not 100% efficient so of the 11.52 kW we get from the EVSE perhaps 10.4 kW are delivered to the battery. In an hour it picks up 10400 Wh which, at 450 Wh/mi means 23.11 mi range added per hour of charging. To add 400 miles would take 400/23.11 = seventeen point three hours (note that I had to spell out the hours as if I put numerals the server hangs). This is, of course, completely tolerable if you drive, say, 200 mi/day. But keep in mind that any charger wired into a 50 A circuit or plugged into a 50 A receptacle (14-50R) can only deliver 40 A legally and will only deliver 5/6 of these numbers meaning 5*23.11/6 = 19.3 mi per hour or 20.8 hours for a full charge. Again acceptable for many applications. Further note that a 14-50R receptacle can be legally installed on a 40 A circuit. In an abundance of caution Tesla has modified its 14-50P adapter to only deliver 32 A should this be the case. 32*240/450 = 17.1 Wh/mi (23.4 hr for a full charge). I think the message her is to select a charger that delivers as much current as possible. This isn't a Leaf you are charging.

Another thing to think about is the future. Will this RIT be the only BEV you will ever charge or will there be an R1S arriving about a year later? How will you charge 2 BEVs? This is something to think about now as clearly you will want a circuit of more than 60A and the rules get a little trickier over 60A. Unless of course, you want to install an entirely separate 60 A circuit. If you live in a house with 200A service this is going to be a challenge which will probably involve a larger service (bigger panel, bigger transformer on the pole...).

One comment on the video: he says a couple of times that your car will be the biggest electric load in your house, That depends, of course, on how much you drive. If you do the average 13,000 miles per year that will be, at 450 W/mi, 6 MWh/yr. I use about 20 MWh/y overall. YMMV and you can look at old electric bills to see what part of your annual use the BEV will take.
 
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ajdelange

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Forgot that info on subscribers current installations was requested.

In Virginia I have a Tesla HPWC on a 100 Amp circuit. As the circuit is above 60 A there is a lockable disconnect installed. It is capable of charging my Model X at 72 A (17 kW). It can be set to charge at a lower rate if desired. It can be set up as a master among other HPWCs on the same circuit and will share power between itself and the slaves. It is NEMA 3R ("Protection against incidental contact with enclosed equipment. Protection from falling dirt, rain, sleet and/or snow. Drainage provision. Protection against rain at a level higher than the lowest live part.") rated, is installed indoors, has a 24' cable. "Smart" and internet charging features are handled by the car. Current consumption is measured by external equipment (eGauge which monitors many loads in the house and the solar panels) as well as being recorded by third party apps which communicate with the car. Car has a 100 kWh battery. Unit costs $450. It does everything it is supposed to do and is fairly attractive.

In the country I have a corded HPWC plugged into a NEMA 14-50R on a 50 A circuit. It charges my X at a maximum rate of 9.6 kW (40A).

None of this will be of any relevance to Rivian owners unless, as many of us daily pray, a SC network deal is struck between Tesla and Rivian, and thus a Tesla to Rivian adapter of some sort becomes available.
 
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ajdelange

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I have to take back the comment about no relevance to Rivian owners as I have just learned of the TeslaTap which would allow a Rivian owner to charge from a Tesla HPWC (but not from a Tesla SC).
 

Lmirafuente

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Thanks for sharing...this was very helpful!

I am in the process of building a new house with solar. Does anybody in this forum have information on how much a EV (Rivian) will add to the consumption of electricity? I guess is we will be around 400kw hours per month without the Rivian....how much will the Rivian add to the consumption of energy?

I do not have an EV to draw first hand experience. Thanks for the help in advance!
 

ajdelange

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That depends on how much you drive it just as the amount you spend on gasoline depends on how much you drive your ICE cars. You start calculations by looking at Rivians statements that the long range version will have range of 400 miles and carry a 180 kWh battery. Simple arithmetic say then that the power consumption will be 180/400 = .450 kWh/mi (450 wH/mi). Each 1000 miles driven then requires 0.450*1000 = 450 kWh. If you drive 1000 mi per month (note that the average American drives about 13,000 miles each year) you will be putting about 450 kWh into the battery meaning that you will be taking something over 500 kWh from the grid/solar as the charger is not 100 % efficient. That's more that your estimated load of 400 kWh/mo which seems awfully low as 400 (kwH/mo) / 31 (da/mo) /24 (hr/da) = 0.538 kW/hr/hr = 0.538 kw average demand. A modest sized home will have an average demand of at least a kW. I have a moderate sized home heated by heatpumps (i.e. electricity) with electric backup heat and averaged 6 kW during the cold months.

To compare to the Solar system get the NREL (National Renewable Engergy Lab) numbers for where you live. Typically April - Jul on the east coast gives us the equivalent of about 5 hours per day of sunlight at the level at which the panels are rated. Thus a solar system rated for 10 kW at peak sun will give about 10*5 = 50 kWh per day. If you are an average user of your vehicle you will be driving 13000/365 = 35.6 miles each day. At 0.450 kWh/mi that will required loading the battery with 0.450*35.6 = 0.94 kWh each day. Thats only about 10% of a 10 kW system's capacity.

California has, I believe, some strange regulations concerning the size of residential solar systems that can be grid tied. For this reason and because your driving habits and home power utilization are likely quite different from the examples given above you really need to consult a professional. It can get complicated fast.
 
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Lmirafuente

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That depends on how much you drive it just as the amount you spend on gasoline depends on how much you drive your ICE cars. You start calculations by looking at Rivians statements that the long range version will have range of 400 miles and carry a 180 kWh battery. Simple arithmetic say then that the power consumption will be 180/400 = .450 kWh/mi (450 wH/mi). Each 1000 miles driven then requires 0.450*1000 = 450 kWh. If you drive 1000 mi per month (note that the average American drives about 13,000 miles each year) you will be putting about 450 kWh into the battery meaning that you will be taking something over 500 kWh from the grid/solar as the charger is not 100 % efficient. That's more that your estimated load of 400 kWh/mo which seems awfully low as 400 (kwH/mo) / 31 (da/mo) /24 (hr/da) = 0.538 kW/hr/hr = 0.538 kw average demand. A modest sized home will have an average demand of at least a kW. I have a moderate sized home heated by heatpumps (i.e. electricity) with electric backup heat and averaged 6 kW during the cold months.

To compare to the Solar system get the NREL (National Renewable Engergy Lab) numbers for where you live. Typically April - Jul on the east coast gives us the equivalent of about 5 hours per day of sunlight at the level at which the panels are rated. Thus a solar system rated for 10 kW at peak sun will give about 10*5 = 60 kWh per day. If you are an average user of your vehicle you will be driving 13000/365 = 35.6 miles each day. At 0.450 kWh/mi that will required loading the battery with 0.450*35.6 = 0.94 kWh each day. Thats only about 10% of a 10 kW system's capacity.

California has, I believe, some strange regulations concerning the size of residential solar systems that can be grid tied. For this reason and because your driving habits and home power utilization are likely quite different from the examples given above you really need to consult a professional. It can get complicated fast.
Thank you!
 

courtier

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I am a newbie when it comes to electric vehicles but I'm really keen to purchase a Rivian later this year (still deciding on R1S vs. R1T). With that said, I'm wondering what would be a recommended EV charger to take full advantage of the Rivian's 11.5 kWh onboard charger? From what I've seen so far, most commonly available EV chargers top out at (only) 40a which would yield slower/lower throughput and longer charging times. Assuming the availability of a 60a (or higher) circuit to feed an EV charger capable of at least 48a that could maximize the onboard charger and provide the fastest charging times, what would folks recommend? A Juicebox Pro 75? A Tesla Wall Connector plus Tesla Tap (now available in 50a and 80a versions)? Something else entirely? And on the last point, what are the odds Rivian develops their own EV charger (similar to Tesla) which might be the preferred choice?
 

ajdelange

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That's a difficult question to answer as it depends not only on what you are planning to do now but also on what you think you may do. Will you add a second BEV? Will you get impatient and buy a Tesla Model 3 while waiting for your Rivian? Will you reserve a CT? Buy an iPace?

At the moment all the vehicles coming out seem to be limited to 48 A Level 2 charging. Thus, at this point in time there doesn't seem to be much point in investing in EVSE capable of more than this. Tesla has made planning a little simpler by discontinuing chargers that deliver more. There are dozens of choices for CCS EVSE at the 30 and 40 A level. Tesla's chargers will go to 48 A and charge a CCS vehicle to that level with the Tesla Tap adapter but before buying one I'd want to see assurance from its manufacturer that it has been tested with Rivian. The Tesla chargers are appealing in that they will charge anything CCS and Teslas and can be shared if you do wind up with more than one BEV. They also seem to be less expensive than many of the others.

The simplest solution for Rivian only is to pull a 50 A circuit to a convenient location and install a NEMA 14-50R receptacle. There are lots of 30 A EVSA that will plug into this and I expect Rivian will supply a portable charger that can be plugged into it as well. Assuming that you want to get the maximum Level 2 charging the Rivian can take you will need to feed the EVSE with a 60 Amp circuit and hard wire it to 48 A EVSE. The most flexible approach would be to pull a 100 A or 120 A circuit to a sub panel in the garage. From this you would route feeders to multiple EVSE of various capacities. You could, for example, install 5 Tesla HPWC, each on its own 60 A breaker in the sub panel and plug 5 cars capable of 48 A charging each in at the same time. As 5*48 = 240 A you clearly couldn't charge them all at the same time as the limit for this subpanel would be 100 A but the HPWC can share the load giving each car 20 A for an allowable total of 100 A.

So were I you I guess I would go with a 120 A sub panel (assuming, of course, that your main panel can support that) on the assumption that some day you will have 2 BEV. I would wait to see if Rivian comes out with EVSE (I'll bet they will) unless you are sure that the second vehicle will be a Tesla. You could, of course, pull a 60 A circuit but I would not do that unless you are either sure that you will never have a second BEV or that pulling a second 60 A circuit in the future is easy.

I'd also look on YouTube, the Tesla forums etc. to get some other peoples opinions.
 

courtier

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Thank you, @ajdelange.

I should have provided more details (the devil is always in the details).

I live in a condo building with a single deeded parking space. The building is 20 years old and pre-dates EV's so there are no community chargers (nor even community parking spaces for that matter). I've received permission from the board to install a charger for my own personal use (at my own cost) which will be fed off of the main power for the building, then the association will bill me for the electricity used (determined either via a physical meter or through a virtual one provided by the EV charger). So with that said, my concern will never be for more than a single BEV vehicle. The building has 600a service so getting a 48a, 60a, or even 75a circuit should not be an issue. And Tesla's just don't do it for me so your other scenario of jumping ship won't happen. ;-) Were things different (private garage in a personal, detached home) I'd probably go with your suggestion of a (very) large circuit and sub panel. But in my case I don't think it would be the best option and most likely not feasible.
 

ajdelange

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That removes several degrees of freedom. You will never draw more than 48 A for which the rules require a 60 A circuit so there is no point in pulling anything bigger than that. So the question now becomes do you want to pull 60A or 50. With a 60 A circuit you can install a 48 A EVSE to get the full 11.5 kW which will let you add about 23 miles range per hour of charging. But you would have to install the EVSE permanently. I'm not sure I'd want to do that in a public space but you know your neighborhood and might be perfectly comfortable. The alternative would be a NEMA 14-50R on a 50 A circuit. That would limit your rate to 19 mi/hr added range but would allow you to use portable charging equipment (possibly that which comes with the truck) if theft or tampering is of concern. I've seen portable chargers inside locked cars with the cables to the charge port and the outlet coming out through a partially open window.
 

DucRider

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That removes several degrees of freedom. You will never draw more than 48 A for which the rules require a 60 A circuit so there is no point in pulling anything bigger than that. So the question now becomes do you want to pull 60A or 50. With a 60 A circuit you can install a 48 A EVSE to get the full 11.5 kW which will let you add about 23 miles range per hour of charging. But you would have to install the EVSE permanently. I'm not sure I'd want to do that in a public space but you know your neighborhood and might be perfectly comfortable. The alternative would be a NEMA 14-50R on a 50 A circuit. That would limit your rate to 19 mi/hr added range but would allow you to use portable charging equipment (possibly that which comes with the truck) if theft or tampering is of concern. I've seen portable chargers inside locked cars with the cables to the charge port and the outlet coming out through a partially open window.
I think your numbers are a bit low.
If we assume 300+ miles to be 325 (the Bolt was 200+ and wound up rated at 238) It think this is on the conservative side given what we have seen from Rivian so far.
If we assume a 93% usable capacity (about average), that gives us about 125 kWh.
325/125 = 2.6 mi/kWh
If we go with 90% charging efficiency (also about average):
1 hour of 40A charging should yield about 25 miles
1 hour of 48A should yield close to 30

Just guessing (we all are) since Rivian has not released any hard numbers, but probably pretty close (or a little low) from what we will see.
 

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And on the last point, what are the odds Rivian develops their own EV charger (similar to Tesla) which might be the preferred choice?
I think Rivian has some intellectual property around charging that is worth waiting to see. They are hiring EVSE positions, which appeared to me to be dev-focused.

My recommendation is to install a 60A circuit, but wait to see what EVSE Rivian & Amazon bring to market (or recommend/provide discounts on). There is plenty of time if all you need to do is mount something to the wall & plug it into a 60A outlet...
 

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There is plenty of time if all you need to do is mount something to the wall & plug it into a 60A outlet...
There is no plug/receptacle rated at 60A, in no small part because code requires anything over 50A to be hardwired.

You can absolutely install wiring capable of handling 60A, but if you want a plug in EVSE will need to put it on a 50A (or smaller) breaker with the appropriate receptacle. Very few people will need to fully recharge overnight on a regular basis. Most will be able to fully recharge from a typical days driving in a couple of hours on a 40A circuit.
 

ajdelange

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I think your numbers are a bit low..
Clearly I used 500 Wh/mi to make the math easy. But that's not a bad number given that Rivian advertises 400 miles range on a 180 kWh battery which works out to 500 Wh/mi assuming 90% charging efficiency. A Better Route Planner assumes, for whatever reason, that consumption is somewhat more than that. Assuming that they are smarter about this than I am my numbers are actually a little optimistic. Keep in mind that these are nominal miles and that depending on how you drive and in what kind of terrain and weather you may get more or less than 2 miles per kWh on average. Perhaps the message should have been that whatever your driving conditions an hour of charging on 50 amp circuit will load 5/6ths as many miles as you would get from a 60 A circuit.
 
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