Does charging at 240 volts cost less than at 120?

[Bill R.]

My electrician says that charging at 240 volts (Level 2) is more efficient (less electricity used) than at 120 volts, thus offsetting the cost of the higher voltage charging equipment. I know it is much faster but had not heard that economic argument before. Does this make any sense?

[Rusty]

My electrician says that charging at 240 volts (Level 2) is more efficient (less electricity used) than at 120 volts, thus offsetting the cost of the higher voltage charging equipment. I know it is much faster but had not heard that economic argument before. Does this make any sense?

Barely yes, and I can't imagine it offsets the cost if you have the time, but there probably is some efficiency benefit to charging at 240. If your electrician knows what it is (if I understand things correctly, I may not) that would astound me.

There's a fixed cost for conditioning the battery. It's the same number of watts at 120V and 240V, but it's a lower percentage of the total watts available at 240V. So 240V will spend less time charging, and hence less watt-hours conditioning the battery during the charge. At least, I think that's how it'll work. I've not heard a definitive answer.

Will that justify the cost of a $2000 SPX install? Ummm.... I don't think so, not very quickly at least. Now maybe the charge circuit in the car operates more efficiently at 240V, but I've not heard anyone claim such. Most of the explanations I've heard about the roughly 4 hours charge at 240V vs. the 8-10 hours charge at 120 involve the amount of energy spent on the TMS.

And the amount of energy you spend on the TMS during charge depends on where you live. Fargo in the winter or Arizona in the summer? Probably a lot. San Diego (guess where I live :-) most of the year? Not so much.

Now if you drive a lot and need to do two-a-day (or three-a-day) charging to avoid burning gas? Yeah, 120 won't do that. I'm taking a wait and see approach, and will convert to 240 not for cost, but for convenience.

[airjim22]

my 2 cents says. yes the 240 is a little more efficient but very minimal. Spas could be heated with 120v or 240v some argued while you waited for the water to heat, you would lose some heat waiting for the rest of the water to heat up. Wiring does have some power heat loss as electrons travel down the line. The 240v gives those electrons a cleaner easier path to the battery, but again very little. I see a 25 foot cord vs a 10ft cord having a bigger impact than the 120vs240 debate.

[Marty]

Another, very minor in most cases, advantage is that the losses in the wiring are related to current and not voltage (I^2R) so that for the same wire length and gauge the losses would be half for 240 than 120. In a well-designed home electrical system the difference would be minimal.

There are lots of other variables that might come into play. such as ambient temperature. In slightly cold climates the waste heat from a 120-volt charge would be generated for a longer time, possibly negating the need for resistance heat overnight if the battery is charged at 240 and then cools. Way too many nits to pick, and likely not a whale of a lot of difference. A kilowatt-hour is for all practical purposes a kilowatt-hour.

[volt11]

So with no significant difference in efficiency, I'm wondering how many people getting 240V chargers feel they need it for faster charging, and how many are getting one just to have it? Even if it only runs you $500, that would have bought somewhere between 3500 and 6000 extra gas-powered miles (depending on where gas prices are likely to go in the next few years) for those times when you ran out of time to fully charge your Volt.

(Personally, assuming I buy one, it honestly will be more in the "just to have it" category.)

[barry252]

So with no significant difference in efficiency, I'm wondering how many people getting 240V chargers feel they need it for faster charging, and how many are getting one just to have it? Even if it only runs you $500, that would have bought somewhere between 3500 and 6000 extra gas-powered miles (depending on where gas prices are likely to go in the next few years) for those times when you ran out of time to fully charge your Volt.

(Personally, assuming I buy one, it honestly will be more in the "just to have it" category.)

I bought one to have the faster charge time. I know my feeble mind will forget to plug it in at night and I could get a quick boost in the morning to get me to work. Even though I have 110 in my garage, it's not a dedicated line, so it may have needed rewiring anyway. So, might as well get the tax credit and the 240V charger installed. I have the charger and it's getting installed on Friday, 12/17.

VIN63 is on the road; I hope to pick it up soon!

[scottf200]

So with no significant difference in efficiency, I'm wondering how many people getting 240V chargers feel they need it for faster charging, and how many are getting one just to have it? Even if it only runs you $500, that would have bought somewhere between 3500 and 6000 extra gas-powered miles (depending on where gas prices are likely to go in the next few years) for those times when you ran out of time to fully charge your Volt.
(Personally, assuming I buy one, it honestly will be more in the "just to have it" category.)

I like the 120v idea because 8-10 hours would easily work overnight. I would like to be able to tell folks that it is that simple to own a Volt as well. Remember most electric only cars will not have that option. Leaf, for example, takes over 20 hours to charge on 120v per their FAQ.

I am considering the 240v because occasionally (weekly) I come home after work and need to go do something else a couple/three hours later. I could then charge twice that day and use little to no gas.

[volt11]

I like the 120v idea because 8-10 hours would easily work overnight. I would like to be able to tell folks that it is that simple to own a Volt as well. Remember most electric only cars will not have that option. Leaf, for example, takes over 20 hours to charge on 120v per their FAQ.

I am considering the 240v because occasionally (weekly) I come home after work and need to go do something else a couple/three hours later. I could then charge twice that day and use little to no gas.

I think we're on exactly the same page. Most people will have overnight to do a full "commute" charge, but it's the ability to get more juice in before, say, going out to dinner later, that seems to be the best reason for the 240V option. Even in one hour at 240V you should be able to add 8-10 miles on electric.

[therfman]

(Puts on electrical engineer hat)

There may be more to this than simple resistive losses. I haven't done a ton of work with high-power electronics, but in many cases, AC/DC converters run more efficiently at higher voltages. This is often the case for computer power supplies, whose efficiency is higher on European voltages than North American. The difference varies depending on load, and can reach 10% depending on design (better designs often have lower variance)

The numbers that we already know (for battery capacity and current usage at the 120V plug) point to charging system efficiency in the low 80% range on 120V. Getting a 10% efficiency gain at 240V may be difficult, but 5% is probably possible. That would save about 0.6 kWh per charge. For me, that's about 5.5 cents.

Unless you charge the Volt three times a day or will use the charger for 30 years (if it's truly standard, that may be possible), there is no economic sense to go to 240V despite the efficiency gain. If the goal is to use the least amount of energy possible, then some gains can be squeezed by going to 220V.

Cheers,

Luc

[maynard]

I just ordered, and paid for, a $490.00 Voltec charger for 2 reasons. The US Govt. will give me a tax refund equal to 50% of the purchase price only until 12/30/2010. Our electric supplier will install a dedicated meter free and the electricity is much cheaper at night. So, I will plug in in the evening but the Volt won't charge until the lower rate times. That would be impossible usng 120VAC. So, yes, 240VAC saves money. I filled out the Edison form with my estimated driving time and miles, and when we would charge. Their estimate is that we will save $195.00 per year doing the charge this way. Not too bad. Now, if we could just get Volts here in Michigan.