Which Uses More Electricity - 120V or 220V?

[Carlos Danger]

I must first state that I know nothing about electricity and the charging rates of EVs. I have owned three MS and bought my wife a MY.
My S has always been charged with a 220 line I had installed. My wife's Y is charged with a 120 line as the slow charging rate doesn't affect her as much as she drives less than me each day.

My car will charge 75-80miles in a couple of hours, while my wife will only get 35-40 miles over ten hours.

As we recently signed up for ComEd Hourly pricing I have more closely been watching electricity rates.

So, my question is - what uses more electricity? The model S or model Y? Or put another way - Does it cost more to charge 80 miles on my S for three hours or 35 miles on the Y for ten hours?

Hopefully this all is clear and thanks for any help!

 

[Cosmacelf]

Charging at 240V is more efficient than at 120V due to power consumption overhead while charging. If you have overnight TOU rates, it is even more pronounced as you end up doing a lot of charging during high cost times on 120V. Depending on your rates, and how much you drive, it can cost an extra $100 - $800 a year charging on 120V vs 240V.

 

[jcanoe]

Your cost per kilowatt-hour (kWh) is set by your electric utility. If you have a time of use (TOU) rate plan it will have a peak rate cost ($ per kWh) and lower off-peak rate depending on the day of the week (Monday through Friday) and on the weekend. The off-peak rate (your cheapest rate) usually applies after a certain hour in the evening and before 0600 or 0700 in the A.M. and may also apply anytime on the weekend. That is why it can be challenging to charge using 120V charging (charging takes much longer for the same amount of energy to be put into the battery, will likely extend beyond the off-peak rate window.)

Whether you charge at 120V or 240V the cost per kWh that you would pay is the same (within the specified TOU hourly window). If you charge the Model Y at 120V the maximum power available is usually 1.4kW. If using 240V charging for your Tesla Model S, depending on the charging circuit, the available power could be almost 8 times more, i.e. 11.5kW. Adding 10kWh to the battery of either Tesla vehicle would take ~1 hour using the 240V charging and ~7 hours using the 120V charging.

The cost to add 10kWh to either Tesla vehicle's battery, assuming you pay $0.20 per kWh during the off-peak window, would be ~$2.00 in either case (120V charging might end up cost $0.30 more due to additional charging losses over the additional time needed to charge. *) The same 10kWh consumed outside of the off-peak rate window could cost considerably more, perhaps 50% more, so $3.00 instead of $2.00 for the same amount of energy (10 kWh.)

* 120V charging has been shown to be approximately 10% to 15% less efficient than 240V charging. So in addition to being faster 240V charging will save you some $ versus 120V charging (could be a couple of dollars a month, perhaps $50 per year cheaper to charge at 240V versus 120V.)

 

[Cosmacelf]

So, in order to put some numbers on this 120V vs 240V question of efficiency, I wrote a calculator to figure it out. You can change a bunch of parameters and see how much more it costs to charge at 120V (scroll down to see calculator): CarCharging.us

 

[ATPMSD]

Here are some simply numbers:

Charging at 120V is roughly 80% effificent, meaning 20% of what you pay for does not go into the battery
Charging at 240V is 90-95% efficient.

 

[Cosmacelf]

Here are some simply numbers:

Charging at 120V is roughly 80% effificent, meaning 20% of what you pay for does not go into the battery
Charging at 240V is 90-95% efficient.

There’s other factors to take into consideration. When charging at 240v, your charging is going to be an off peak rates if you are on a TOU plan, whereas at 120V, a lot of charging will be at a higher rate.

 

[ewoodrick]

I must first state that I know nothing about electricity and the charging rates of EVs. I have owned three MS and bought my wife a MY.
My S has always been charged with a 220 line I had installed. My wife's Y is charged with a 120 line as the slow charging rate doesn't affect her as much as she drives less than me each day.

My car will charge 75-80miles in a couple of hours, while my wife will only get 35-40 miles over ten hours.

As we recently signed up for ComEd Hourly pricing I have more closely been watching electricity rates.

So, my question is - what uses more electricity? The model S or model Y? Or put another way - Does it cost more to charge 80 miles on my S for three hours or 35 miles on the Y for ten hours?

Hopefully this all is clear and thanks for any help!

Which uses more electricity is essentially the answer to "Which car drives most"

How much energy you use is irrelevant to the voltage of the circuits. How much you use in in kWh or Wh. The cars user around 250-300 Wh per mile (0.24-0.3 kWh) (although the Model S probably uses a little bit more)

But since most 120V circuits charge slower than 240V circuits, the 120V circuit uses less wHs.

The wall circuit is 120Volts @15amps in 1 hour, it will use 120V*15A*1Hr = 1800 watts (1.8 kW) per hour
The 240 circuit is probably 50A so it would use 240V*50A*1h= 12000 watts (12.0 kW) per hour

The kWh is what your electric bill is based on.

So 80 miles at 300wH = 24,000 wH (24 kWh)
35 miles at 300wH = 10500 hW (12.5 kWh)

So which would use more? the Model S, because it drove further.

The difference in charging speeds is like comparing a standard gas hose that you fill your car (about 1 inch) to the host that the truck uses to fill the gas station tanks (about 5 inched). 50 gallons takes a lot longer through the smaller host than the bogger hose.


The ONLY thing that really make s difference is that if you are using an hourly rate, then it is probably a time of day rate. The 240 charging solution can probably charge a car within the lowest rate period. But as you are aware, the 120V solution may not be able to .

 

[ATPMSD]

There’s other factors to take into consideration. When charging at 240v, your charging is going to be an off peak rates if you are on a TOU plan, whereas at 120V, a lot of charging will be at a higher rate.

Obviously charging at 120v takes longer and can result in charging outside of the lower rate, which drives up cost.

 

[ATPMSD]

The wall circuit is 120Volts @15amps in 1 hour, it will use 120V*15A*1Hr = 1800 watts (1.8 kW) per hour
The 240 circuit is probably 50A so it would use 240V*50A*1h= 12000 watts (12.0 kW) per hour

You also need to consider the 80% rule and charging efficiency:

120V / 15A Circuit is 120v * 15a * 80% (80% rule) = 1.44 kWh (what you pay for) * 80% (efficiency) = 1.152 kWh (what reaches the battery)
120V / 20A Circuit is 120v * 20a * 80% (80% rule) = 1.92 kWh (what you pay for) * 80% (efficiency) = 1.536 kWh (what reaches the battery)
240V / 50A Circuit is 240v * 50a * 80% (80% rule) = 9.6 kWh (what you pay for) * 95% (efficiency) = 9.12 kWh (what reaches the battery)

 

[ewoodrick]

You also need to consider the 80% rule and charging efficiency:

120V / 15A Circuit is 120v * 15a * 80% (80% rule) = 1.44 kWh (what you pay for) * 80% (efficiency) = 1.152 kWh (what reaches the battery)
120V / 20A Circuit is 120v * 20a * 80% (80% rule) = 1.92 kWh (what you pay for) * 80% (efficiency) = 1.536 kWh (what reaches the battery)
240V / 50A Circuit is 240v * 50a * 80% (80% rule) = 9.6 kWh (what you pay for) * 95% (efficiency) = 9.12 kWh (what reaches the battery)

Which is WAY OVERKILL for someone who started out saying that they don't know electricity. I was stretching just using the simplified equations that I did.