220 or 110

220 or 110

If I will not be driving my car for a one month period, (storing it inside a garage) does it matter which outlet I use to keep it plugged into?

220 or 110?

another dumb question..............will not driving the car for a month "hurt anything"

red p85+ howard in cinci

shop | 28. Oktober 2013

No and no.

Charging off 110 is less efficient than charging off 220, so if you have the choice, use 220.

nickjhowe | 28. Oktober 2013

To reinforce @shop, charging off 110 is WAY less inefficient than 220. So definitely leave it plugged into 220. And no, it won't hurt anything.

Panoz | 28. Oktober 2013

I am not an owner, so I am not knowledgeable. For this owner's question, however, if he's gone a month, efficiency doesn't matter, does it? 110v will most certainly get his car to whatever charging level he needs and maintain the battery. I don't see why he should use 220v.

mrspaghetti | 28. Oktober 2013

@nickjhowe - I think you meant "110 is WAY more inefficient", or alternately, "110 is WAY less efficient" :)

jat | 28. Oktober 2013

For the little power being drawn to keep the battery charged, I don't think the efficiency makes much of a difference. Use your normal charging method, but if all you have is 120V that is totally fine.

Mathew98 | 28. Oktober 2013

Keep it charged to 50-62% for your month long vacation to keep the battery pack in optimal storage condition.

Pungoteague_Dave | 28. Oktober 2013

Either option can maintain your car, but why would you not plug into the 220? There's no electricity cost savings with either and the car will be in the same state when you return. I feel a bit "safer" knowing the car is hooked up through the more robust 220 vein, seems less likely to trip a breaker if there's a surge, but I have no evidence to support that - just seems more solid and natural to hook up to the more powerful source. Also, with a HPWC, if you have one, there's no cord hassle.

shop | 28. Oktober 2013

@Panoz - 220 being more efficient means that less total electricity is drawn from the wall with 220 versus 110 charging. So it is cheaper to plug into 220 than 110. There are electrical conversion losses which are more pronounced with 110.

DTsea | 28. Oktober 2013

Where does it say 110V is less efficient?

Heat loss in charging is proportional to current squared, so at a GIVEN POWER LEVEL 220 is better (half the current for a given power level). However, if your 220 line is charging at 40 amps, that is 4x the power of your 110V line (16 times the heat loss).

So for maintenance trickle charging, minimum current minimizes loss.

The loss is trivial anyway... if you assume 5 kWh per day parked (equal to 15 miles vampire drain) that's 5 hours on a 1 kW line (110V at 10 amps) or 30 minutes on a 240 line at 40 amps.

Alternatively you could plug it into 110V, limit it to 3 amps, and it would charge nearly continuously at a trickle level. That would minimize heat loss.

If you have lower rates at night though you would want to set for night-time only charging.

shop | 28. Oktober 2013

It doesn't say it anywhere, but people have measured power into the car and power used from the wall using wattmeters and have found 220 to be more efficient by like 30% or so if I remember correctly.

shop | 28. Oktober 2013

Search these forums ( or on TMC to find that post...

Bighorn | 28. Oktober 2013

I left my car for a month on a 110V line because the car was new and I hadn't fashioned my NEMA 6-20 adapter yet. I had it set to charge to about 60%, but when I was playing with my Tesla app in Paris (and who wouldn't?!), I hit "start charging" and it changed my charge level to full standard range ie 90%. No big deal, but I was stuck with that decision.

PapaSmurf | 28. Oktober 2013

I would let it drop down to the 50%-60% area before leaving for a month, then set the max charging amount to 60%. Then plug it in to a 220v and go.

TeslaDC | 28. Oktober 2013

If you are comparing the efficiency and/or cost differences on "maintaining" (i.e. not "actively charging") the battery between 240V and 120V, then I'd say the differences are negligible.

Per the owners manual, the battery level drops by 1% per day when not plugged in. Taking a 85kWh battery pack as an example, 1% of drop is equivalent to 850Wh/day of drop, equivalent to 35.4W of power loss per hour, continuously in a 24-hour period. In order to keep up with such loss, the drain (when plugged in) on the circuit will be either at 120V @ 0.295A, or 240V @ 0.148A. The power line transmission loss at such low amperes will be too impractical to worry about, though the difference is nonzero. Please correct me if I'm wrong. Thanks.

Bighorn | 28. Oktober 2013

Not questioning your overall assertion, but the vampire losses are not continually being replenished. The car charges when it loses a certain number of miles (or percentage loss, perhaps), so it charges in fits and starts at the current at which it's set to operate. So it would still charge at 40 amps (on a NEMA 14-50), not 0.148A when the time came.

michael1800 | 28. Oktober 2013

hehe Geeze we're a bunch of geeks. Simple questions end up being great, interesting discussions and a deep look at the minutia. Still though, like shop states, "No and no."

Brian H | 29. Oktober 2013

"No and no" is right. Anything else is straining at gnats.

soma | 29. Oktober 2013

I believe that the "inefficiency" of the 110v charging is actually due to the vampire drain in the background -- because for the 3 mph that is charged, 1 mph is lost. For a 200-240v charge, this is more negligible, but for 110v it is significant. Otherwise 110v charging is not inherently more inefficient than 200-240v.

When you are plugged in and leaving the car for a long time, vampire drain is all that you are compensating for. So it does not matter which you plug into.

DTsea | 29. Oktober 2013

@soma +1

djm12 | 29. Oktober 2013

Our Model S has been on 110V charging since May - and of our 6000 miles driven, about 5000 of those have been on 110V. So, reliability speaking, I have no reason to believe long term use of 110V would be any cause of concern.