twin charger options for 40 kWh

twin charger options for 40 kWh

I'm going to be getting the 40 kwh and inquiring with people what is their decision making process in deciding whether or not the twin chargers are a smart option or not.

I don't plan on driving over 50 miles per day which is reason for my 40 kwh purchase and I will be home for at least 7-8 hours per night...if i go on trips, i'm just going to drive the family SUV and not use the Tesla...

Is there any reason for getting the twin charger to increase the charge to 62 miles per hour instead of the normal 31 miles per hour?

The purchase for the package at $2500+ is modest, but still an additional cost i'm not sure is justified...

Why are you purchasing/not purchasing the faster charging package for your use? So you can get in and out faster? The more and more i look at it...if i get into a routine every night plugging in and i never drive more than 50 miles per day, there's no need to get it....

nickjhowe | 1 febbraio 2013
Tranman | 1 febbraio 2013

Thanks Nick...

based on my details that I'm not using this car for long trips and don't drive nearly enough miles...the decision is clear to not get it period...

nickjhowe | 1 febbraio 2013

The only time you need it is if you run the car low and need to go home and then go back out sooner than 31 m/h but 62 m/h would be OK. Pretty small use case.

Or if your local Utility was offering you some weird incentive.

Mark K | 1 febbraio 2013

This is actually a very interesting question.

I ordered an 85 for me and a 40 for my wife. She drives 25 miles a day, so the 40 was plenty. We have 5 cars already so we have lots of options for long trips.

At first, I thought why bother with the twin chargers? The 85 has SC capability, and the 40 can charge in 5 hours with a single 10kW charger.

Then I got to thinking ... how do I manage charging both of these cars overnight? The off-peak rates are considerably lower, and those hours start getting limited if you want to top off both cars.

I began to realize it is a very useful liberty to do home refills in half the time. It makes it easier to stay in off-peak rates, and lets you top off quickly between morning and evening driving.

My wife's use case is lots of short trips centered around our house as the hub. With the twin chargers, she can refill the 40 mid day in a 60 minute pit stop at home. That makes the 40's useful range quite a bit more for her kind of lifestyle.

Further, there is a kind of weird ratio with the 40/Twin - A small battery with a big charger. You can put in coulombs at a 20kW rate, so you can fill it from near empty in about two hours. That's pretty good.

Not useful for every lifestyle, but at 1,500 bucks it seemed worth it for us.

DouglasR | 2 febbraio 2013

I wonder how long it would take for the off-peak rate savings to add up to $1500?

I could see this as a good option for someone living in southern Canada, where there is a network of 70 amp charging stations, however.

travis.johnson | 2 febbraio 2013

I didn't get the twin chargers. We are driving a Leaf now and it charges at 12 mi/hr. That's good enough. There hasn't been a time where we couldn't take the Leaf because it hadn't charged fast enough. We will have over 12,000 miles on it the first year.

The standard 30 mi/hr rate that the single 40A charger offers will be perfect. And, all of the public charging stations I've installed are 30A so....

You might check and see if your house panel can even support 70A.

I say skip the dual chargers.

jat | 2 febbraio 2013

Personally, I think the need for fast charging is higher with a smaller battery -- ie, you are more likely to need to charge it at times other than overnight, while a larger battery has plenty of range for unexpected trips. When you do need to charge between trips, you will want to recover the charge as quickly as possible.

When I was driving the LEAF, which admittedly has a significantly shorter range than the 40kWh Model S, there were occasions where I got home with an empty battery and needed to make other trips. On occasions, we went out in my wife's Civic, and other times I let it charge for an hour to get back 7mi range -- it would have been convenient in those cases to have much quicker charging available.

mpottinger | 2 febbraio 2013

At an average total use of 30 to 50 miles a day, I just couldn't justify forking over an extra 10 or 20k for capacity I will rarely use and one less second to 60 miles an hour, which while nice to have just isn't a necessity during typical driving. If money were no object, maybe, but that's not me. Like me, your daily charge time is likely 2 hours or so. My need for a one hour daily charging capability, just isn't there. I'd rather have the pano roof.

Objective1 | 2 febbraio 2013

"The standard 30 mi/hr rate that the single 40A charger offers"

My reading of the reports of current owners is the that those are 30 IDEAL (55 mph no Heat or AC) miles. Real life miles charged per hour @40A will be substantially less.

Also, charge rates are not constant. As the 40 kw/h fills up, charge rate will slow.

So, for fast recharging of 40 kw/h, twin chargers and > 40A might be handy.

portia | 2 febbraio 2013

Ah, don't forget that the twin charger is ONLY useful when you have the HPWC. And I couldn't get the HPWC without significant upgrade to the electricity coming to our house (only 100amps), so even though I have the twin charger, it is not saving any time on the NEMA 15-40A I have. When using the Superchargers, the twin charger is also not used.

jkirkebo | 2 febbraio 2013

Here in Europe we will soon have access to a boatload of 22kW charging points so the second charger will be very useful for public charging. You might eventually get quite a few 80A J1772s in the US too I'd guess.

DouglasR | 2 febbraio 2013


"Ah, don't forget that the twin charger is ONLY useful when you have the HPWC."

The HPWC is only useful when you have the twin chargers, but the reverse is not correct. There are many instances where the twin charger is useful without the HWPC. I am having the charger installed next week, and I don't have an HWPC. The twin chargers are useful if you want to take advantage of high amperage power sources.

markapeterman | 2 febbraio 2013


250v/40amps is 10kW/hr so ~4 hrs to fill a 40 kWh battery.

The hours per charge thing (ideal vs. rated) is just a way to think about it. 30 mi/hr of a 300mi ideal charge is the same as 24mi/hr of a 240 mile rated charge.

The charging does not slow unless you do a range charge and only at the very end.

Since only ~32-35kWh are available in a standard charge (my guess) - a 14-50 plug should easily recharge the entire battery in 3-3.5 hrs. Twin chargers and a HPWC will cut that in half.

IMO, I would get the 60kwh before spending $2700 on that.

Mark K | 2 febbraio 2013

Mark P -

You don't need the HPWC to benefit from the 20kW twin charger, just a sufficient electrical feed.

So at $1,500 the 20kW charger is $8,500 less expensive than the 60kW battery.

It really depends on your usage pattern. If you want to go out of town often, get the biggest battery you can.

If you drive mostly in the city, the 40kW with a fast twin charger can be a very interesting alternative. (It's not viable for road trips, in my opinion).

Besides costing $10K less, the 40KW is also about 500 lbs lighter than the 85.

The upshot is that each buyer should really think realistically about their usage pattern to choose the right combo. It's surprising how different the right answer can be for each driver.

I am 3146 | 3 febbraio 2013


The HPWC is very convenient way to charge at home even without the dual chargers. Even if there isn't a dual charger installed in the car, you can charge multiple vehicles without constantly pulling out the travel connector. The HPWC has a selectable amperage output depending on the feed circuit.

The dual charger with the HPWC gives you the fastest option at home.