Is it more cost effective to charge at 48 amps or 32amps?

[Irodger199]

Hi , so my question is what is more cost effective Charging at 48 amps or 32 amps. I know 48 will be faster then 32 . What would the cost difference be between higher but faster versus lower but longer . Any help greatly appreciated. Thanks

 

[Thp3]

Rear wheel Model 3 can only charge at 32 amps with its onboard charger.

LR and Performance can charge at 48 amps.

In the USA, the electricity cost is in Kwh. So charging fast or slow cost the same if you charge the same Kw.

 

[MLXXXp]

If you can do it, charging at 48 amps would be cheaper. This is because of the extra "wasted" power that the charging electronics draws in addition to the actual power going into the battery. This extra power is basically constant regardless of how much is going into the battery, so the longer you're charging, the longer (thus more) you're paying for this "overhead" power.

Also, in cold weather extra "wasted" power may be needed to keep the battery warm enough for charging. Just like the charging electronics, the shorter time you have to keep the battery warm, the less cost for this wasted power. Plus the extra current going into the battery may cause it to "self heat" more, due to it's internal resistance, thus requiring less power for external heating.

And as an aside, if your installed 48 amp circuit has thicker wire than a 32 amp one would, you also end up with less power loss in the wiring from the panel to the EVSE due to that wire's lower resistance.

 

[ucmndd]

The difference is negligible/pennies.

32 = more parasitic loss from the car being powered

48 = more loss to resistance/heat.

It’s not worth thinking about.

 

[roblab]

Of course, if you slow down while driving you'll save a lot more than you will by charging at one speed or another, yet not many worry about that.

Just drive your car and enjoy it. Quit worrying about pennies.

 

[3sr+buyer]

The cost that may matter is if you already have 32A charging in your garage, but it would be expensive to add or upgrade to 48A charging.

 

[Aither]

The difference is negligible/pennies.

32 = more parasitic loss from the car being powered

48 = more loss to resistance/heat.

It’s not worth thinking about.

The above answer is spot on, with one caveat. 32A is 7.68kW, and 48A is 11.52kW. Depending on you electrical utility they may have different rates for different peak operations draws. Charging at 48A will potentially increase your peak by 3.84kW. If this puts you into a higher rate class, it may increase your overall power bill.

You may want to ask your electricity retailer if you have a variable or stepped demand fee and determine if the charge rate might put you over.

Also keep in mind that charging at the lower rate puts less stress on the utility system. If everyone did this it will reduce the need for system upgrades and help keep costs down for everyone.

 

[davewill]

The difference is negligible/pennies.

32 = more parasitic loss from the car being powered

48 = more loss to resistance/heat.

It’s not worth thinking about.

Yes, yes, yes. My take is that unless you are coming home with a low battery and needing to leave again in 4 hours on a regular basis and/or have no Superchargers around, 32a is entirely adequate.

As far as I'm concerned, unless you're talking about 120v charging, efficiency really isn't a critical factor.

 

[Rocky_H]

The above answer is spot on, with one caveat. 32A is 7.68kW, and 48A is 11.52kW. Depending on you electrical utility they may have different rates for different peak operations draws. Charging at 48A will potentially increase your peak by 3.84kW. If this puts you into a higher rate class, it may increase your overall power bill.

This is one of those theoretical things though. You would be hard pressed to find any RESIDENTIAL electricity rate plans in North America that figure in power level demand charges. This is commonly a thing in industrial electricity services, though. I did just hear about one place this past week, though, but that was the first I've ever heard of it coming up in 8 years of reading this forum. So they do exist, but it is very unlikely anyone reading this has that for their house.

 

[Aither]

This is one of those theoretical things though. You would be hard pressed to find any RESIDENTIAL electricity rate plans in North America that figure in power level demand charges. This is commonly a thing in industrial electricity services, though. I did just hear about one place this past week, though, but that was the first I've ever heard of it coming up in 8 years of reading this forum. So they do exist, but it is very unlikely anyone reading this has that for their house.

Which place did you hear about this past week? Rare today has an uncanny way of becoming common tomorrow.

 

[cwerdna]

I've heard of demand charges on a residential plan being a possible choice in Arizona: Frequently Asked Questions.

Electricity for West Texas and Southern New Mexico | El Paso Electric | Texas Rate Case FAQs mentions a proposal:

Are EPE’s residential rate structures changing?
No, the rate structure is not changing. EPE is proposing to change the Summer Season, currently May to October, to June through September. EPE has also proposed opening the Experimental Demand Charge Time of Day optional rate to any residential customer. EPE continues to encourage energy conservation through its rate structures to reflect and recover its costs more accurately. The summer rates are designed to be higher when customer demand for electricity is highest and EPE’s system hits annual peaks. Rates will continue to be lower during non-summer months.

While searching for something else, I found Residential Demand Charge – Columbia River PUD.

I do agree they're quite rare for US residential plans.

 

[SageBrush]

Norway is starting country wide demand charges for residential. I expect the same any place where EV marketshare approaches Norway levels

 

[Aither]

I do agree they're quite rare for US residential plans.

Lethbridge in Alberta Canada, and San Luis Valley/Unites Power in CO have residential demand. As we encounter more bottlenecks with distribution as a result of residential charging, the residential cost of service will be tied to demand. The more capacity you use, the more you will pay for - which is fair in my mind.

 

[BillRadio]

Which place did you hear about this past week? Rare today has an uncanny way of becoming common tomorrow.

Our electric co-op started charging by the kw, on-peak. After 8pm, we can charge at any rate.

"Rate Redesign - CORE"

 

[black knight 3]

My primary concern isn’t cost but preservation of battery life. I usually limit charging to 24A instead of 32A to produce less heat, the slower the better and most folks have enough time to charge overnight.

 

[cwerdna]

These two folks in the US also mentioned demand charges:

Optimal Charging Amperage

I have yet to run into an issue of the app refusing to set scheduled departure. If you do, just program it directly in the car. My app "forgot" several times. I'm paranoid now and checking all settings every time I update the app or car software. I like the idea setting it up in the car if it's...

teslamotorsclub.com

One for sure is referring to a residential plan and the it's likely the other one was too.

 

[Rocky_H]

My primary concern isn’t cost but preservation of battery life.

That is a good concern, but

I usually limit charging to 24A instead of 32A to produce less heat, the slower the better and most folks have enough time to charge overnight.

...that is irrelevant to your battery. It won't notice or care in the least about you dinking around between the difference of 6 or 7 kW when it is a battery that can handle over 200 kW. That's an unnoticeable difference.

I'm not saying that is bad to do--it's fine. But I want to make sure people do understand that it's not making any difference to their batteries. There is possibly some benefit to not running the charging cable at the maximum level it's rated for. They can get kind of warm, and that daily cycle of heating up and cooling down can cause some wear on electronics and solder joints and such. So it might extend the life of your charging cable some, and I do recommend having it down a few amps for that reason.

 

[black knight 3]

That is a good concern, but

...that is irrelevant to your battery. It won't notice or care in the least about you dinking around between the difference of 6 or 7 kW when it is a battery that can handle over 200 kW. That's an unnoticeable difference.

I'm not saying that is bad to do--it's fine. But I want to make sure people do understand that it's not making any difference to their batteries. There is possibly some benefit to not running the charging cable at the maximum level it's rated for. They can get kind of warm, and that daily cycle of heating up and cooling down can cause some wear on electronics and solder joints and such. So it might extend the life of your charging cable some, and I do recommend having it down a few amps for that reason.

noted, thank you.

got most of that advice from a youtube clip on optimized charging habits(around 15:40 into clip):

seems to be harmless, may help but won't hurt and would love it if i can keep my 405 miles range at 90% or greater after 3 years..

 

[Payne95831]

32 amps or 48 amps
My utility would give me a $500 rebate for installing a wall charger but only if a max of 40 amp breaker was installed. So I opted for a 60 amp breaker with 4 gage wire and gave up the rebate. I assume then that the grid engineer's are concerned about what if everyone charged up at the same time that the lower amp capability would be better for everyone. So I have only changed at my full rate capability when I need it fast then charge at 32 amps like as if I had installed the utility preferred 40 amp breaker all other times. Also I only charge to 60% because normal daily use is about 20% or less of capacity. The idea to further go low stress on my battery for a planned long term battery life. If it makes no difference and potentially beneficial to the long term battery health then I will continue the practice.

 

[Jedi2155]

The real answer is that the onboard AC-DC charger has different efficiencies at various power levels combined with parasitic losses of the vehicle being powered. It's been a long time since someone has actually measured the differences.

Most power supplies (i.e. the charger) have an efficiency curve like this, but there's a loss at lower end as well. So peak efficiency is typically between 45% to 80% of load. So for a 48A equipped Tesla it would be closer to 22A to 40A, and for the 32A model, optimal efficiency is probably between 16 to 26A.