Charging Efficiency

[dogememe]

I currently charge my Volt at home every night.

My question is the efficiency of charging at home. At home I plug into an old outlet that already gets slightly warm at 8A so I don’t want to try 12A.

The landlord where we rent said if we pay to install EV charger he will deduct it off the rent.

Initially I wanted to wait for the new Tesla Universal charger to come out and have that professionally installed. But I’m thinking to keep it simple, why not just have an electrician run a new circuit and put in a nema 14-50 outlet. Then use an 14-50 to 6-20 adapter off Amazon to use my Schumacher SC1455 in level 2 mode.

The reason that would be fine is my Volt can only charge at 3.3Kw anyway. So why spend big bucks on a more capable hardwired level 2 charger for ~$600 that’s going to be wasted.

My question is how much more efficient would it be on our power bill to charge it through the level 2 (240v) vs level 1 (120v 8a) like I do now? As I understand there is overhead and the overhead is basically fixed. Which is why 12a mode even at level 1 is almost double the speed of 8a charging?

Thanks.

 

[eljefino]

How long to you plan to rent where you are?

Are you rent controlled?

I would expect your landlord to raise your rent after you invest in the place, since you'll have something you can't take with you.

If you don't NEED to charge any faster, I would keep puttering along at Level 1, and save your money for a house.

To answer the question, it's in the weeds, electrically, how fast you charge insofar as battery capacity vs what you pay for.

If you have access to the fuse box, you can kill the power and change the outlet with the help of good old youtube. Put in a commercial grade one, noone will ever know. Then you can run 50% faster.

 

[dogememe]

How long to you plan to rent where you are?

Are you rent controlled?

I would expect your landlord to raise your rent after you invest in the place, since you'll have something you can't take with you.

If you don't NEED to charge any faster, I would keep puttering along at Level 1, and save your money for a house.

To answer the question, it's in the weeds, electrically, how fast you charge insofar as battery capacity vs what you pay for.

If you have access to the fuse box, you can kill the power and change the outlet with the help of good old youtube. Put in a commercial grade one, noone will ever know. Then you can run 50% faster.

I understand your concern about raising the rent after investing in the property. That's why I figured keeping the cost down would be a good idea, and paying the electrician to run the 240V circuit and installing a good 14-50 would be best. If we wanted to get a proper Level 2 charger later instead of using my Level 1 & 2 combined Schumacher SC1455 there are plenty of good models that can plug in to the outlet if I go to pure EV down the road and need something that charges at a quicker rate. But my Volt can't charge faster anyway!

 

[JohnnyG]

I don't think you'll save any money in the long run. I had a Volt and I know that they can strain a 110V outlet. I even had a dedicated single 110V outlet not 12" from my breaker box and it still got warm to the touch.

Saving money aside, I'd do it just for the peace of mind and maybe a little faster charging speed. That way you could take FULL advantage of any off peak electricity pricing and not worry.

 

[supton]

If it gets warm I’d check it out. Maybe the contacts are worn and it’s time to replace, they don’t last forever. Or worse, it’s backstabbed (I hope not!). Easy enough to check.

Are you after efficiency or just cost? You could put one of those killawatt meters on, measure current draw, measure power draw, then time it. Then see how much the battery went up to. The delta of the battery state divided by power draw would get you efficiency, but I’m not sure that is what you are after.

 

[The Critic]

A quality hubbell 9450 outlet is around $100 now. These are the only ones that are proven to work safely and reliably under EV use. Your electrical panel may/may not allow for a 50A circuit to be ran for a 14-50 outlet anyway, have you done the proper load calculations? Hint: if you don't have 200A service, it won't be likely.

Also, the real issue is that 2017NEC code technically requires NEMA 14-50 outlets used for EV charging to have a GFCI breaker. Between the cost of the GFCI breaker and the Hubbell outlet, you may as well go hardwired.

 

[Rand]

Just charge at 12 amps and see how hot it gets the landlord should be fixing it if its faulty.

Were you just talking about getting out of debt and moving? or was that someone else?

 

[dogememe]

Just charge at 12 amps and see how hot it gets the landlord should be fixing it if its faulty.

Were you just talking about getting out of debt and moving? or was that someone else?

That whole thing is not going to happen. It was not going to work out. So I'm renting with my new partner.

 

[The Critic]

So I'm renting with my new partner.

That was quick.

 

[brianl703]

Also, the real issue is that 2017NEC code technically requires NEMA 14-50 outlets used for EV charging to have a GFCI breaker. Between the cost of the GFCI breaker and the Hubbell outlet, you may as well go hardwired.

Not all states have adopted the 2017 NEC and even if they have, they may have amended it to remove the requirement for a GFCI on 240V outlets.

 

[The Critic]

Not all states have adopted the 2017 NEC and even if they have, they may have amended it to remove the requirement for a GFCI on 240V outlets.

My understanding is that 2020 NEC requires GFCI for this purpose and no longer has the leeway that some states employed with the 2017 NEC. CA also adopted the 2020 NEC effective 1/1/23.

 

[brianl703]

My understanding is that 2020 NEC requires GFCI for this purpose and no longer has the leeway that some states employed with the 2017 NEC. CA also adopted the 2020 NEC effective 1/1/23.

States (or localities, depending on how it works in that particular state) always have the option to amend the NEC as they see fit. Virginia did such to modify the requirement for AFCI breakers, requiring them only on bedroom circuits. I can't say for sure that any states (or localities) have amended the NEC to remove the requirement for 240V GFCIs, but it seems likely given the expense.

They can also go the other way and amend the NEC to be more strict. One example is how much of the Chicago area has a requirement that conduit be used in residential construction. Romex is not allowed.

 

[MVAR]

You won't save any money between charging at 120V vs 240V. You're not billed on amperage drawn but kWh used. Your real power(watt) consumption isn't going to change so neither will your bill.

 

[PandaBear]

Efficiency of Charging at 220v versus 120v?

I am trying to decide whether to shell out for a 220v outlet in my garage for my Model 3. Does a charge cost less when it's 220v than when it's 120v? If so, how much of a saving is it?

teslamotorsclub.com

I think the 80% vs 90% may not be exactly set in stone accurate, but based on most computer power supply's efficiency between 110V vs 220V, I'd say 5-10% difference is typical. So you basically can check if your electricity cost is going to make that big of a difference and whether you will get your investment back (even if landlord pay for it he/she can always increase rent later, or you may leave and he never paid you 100% back, not sure how is the term laid out). If you cannot finish charging daily and 220V really helps, then that's probably a good reason. Maybe not Volt, so it is probably going back to your 5-10% savings on electricity calculation.

 

[PandaBear]

You won't save any money between charging at 120V vs 240V. You're not billed on amperage drawn but kWh used. Your real power(watt) consumption isn't going to change so neither will your bill.

There is a slight electrical loss difference on the same power draw, between 120V at 8A vs 240V at 4A. It is not a lot but a small amount for sure (5-10%). That loss is in the wire heat (IxR) assuming the power electronics in the car is the same.

 

[ripcord]

The efficiency advantage of 240v is because it takes half the amperage to deliver the same amount of current. Higher amperage is always less efficient because of the extra resistance and heat loss over the wire.

 

[JavierH19]

A little bit of heat is ok. I assume you're using 240v, most garages have a 240v outlet.

 

[MVAR]

There is a slight electrical loss difference on the same power draw, between 120V at 8A vs 240V at 4A. It is not a lot but a small amount for sure (5-10%). That loss is in the wire heat (IxR) assuming the power electronics in the car is the same.

I understand I2*R (can't seem to get the squared to work in browser or copy over from Word) losses. I've never seen losses great enough to warrant a difference in billing or even an actual measurable difference on a meter utilizing equipment of the same real power (w) rating but differing voltages. This was even covered in live simulations during my apprenticeship years ago. Short circuit lengths in residential housing mitigated these losses. I would venture a guess that the majority of the heat he is experiencing is from a worn socket(poor connection).

 

[brianl703]

There is a slight electrical loss difference on the same power draw, between 120V at 8A vs 240V at 4A. It is not a lot but a small amount for sure (5-10%). That loss is in the wire heat (IxR) assuming the power electronics in the car is the same.

Having done some calculations for voltage drop on extension cords, at 8A the voltage drop is not nearly 10% unless the circuit is exceptionally long, like over 200 feet (assuming it's wired with the required by code 14AWG wire).

 

[y_p_w]

I understand I2*R (can't seem to get the squared to work in browser or copy over from Word) losses. I've never seen losses great enough to warrant a difference in billing or even an actual measurable difference on a meter utilizing equipment of the same real power (w) rating but differing voltages. This was even covered in live simulations during my apprenticeship years ago. Short circuit lengths in residential housing mitigated these losses. I would venture a guess that the majority of the heat he is experiencing is from a worn socket(poor connection).

I've heard a lot of comments when I mentioned my dad had a handyman installed a Leviton NEMA 14-50 outlet. That being said, the outlet is maybe 3 feet (using extremely thick cable) from the breaker and even if the connection isn't that solid (seems to be the biggest compliant about Leviton) it's the entire circuit that results in resistance.

Wondering if maybe it should re-done with a Hubbell or Bryant outlet.