8 ms·

To be pedantic, it is not that 120 V is not enough. It's that the amount of current you need at that voltage is prohibitive because of wire sizing, which is nee

To be pedantic, it is not that 120 V is not enough. It's that the amount of current you need at that voltage is prohibitive because of wire sizing, which is needed to minimize resistive voltage loss and dangerous wire overheating.

iyulaev 14y ago
Absolutely right. I was using 120V as shorthand for "the 120V/20A circuit that we're all used to."
- zanny 14y ago
  I don't think saying "120v isn't enough, you need to rewire your entire house" is really accurate either. Most water heaters, stoves, and some central heaters run off a merged breaker for 240v. You can easily use one of those lines for the car if you don't plan on taxing the thing the entire time (though I figure if you have 50k for a car you have 1k to add an extra circuit and wire your garage up for it). Also, 240v cars makes so much more sense in a world where 99% of people use 240v outlets, and in the US you can just oscillate two 120v's and get a usually-good-enough 240v signal.
- iyulaev 14y ago
  I don't think saying "120v isn't enough, you need to rewire your entire house" is really accurate either. Most water heaters, stoves, and some central heaters run off a merged breaker for 240v. You can easily use one of those lines for the car if you don't plan on taxing the thing the entire time (though I figure if you have 50k for a car you have 1k to add an extra circuit and wire your garage up for it). Yes, although at least in my view part of the selling point is that we have plugs everywhere, so you have electricity anywhere right? Well, hunting around for a 240V plug is a big harder than 120V. Also, even though 99% (???) of the world is on 240V, I think the current rating on those circuits still limits power to around 2kW sustained.
  - stephen_g 14y ago
    I'm in Australia, and our power supply is 230V AC (+/- 6%) (240V was the standard before 2000, but is still within the acceptable limits). Most power outlets are 10A (max ~2300W) but I also have two 15A sockets in my house for the air conditioners (3450W - I also use one to power my coffee machine, which pulls 3200W when warming up!), and could theoretically get a 20A socket (4600W) installed. With an industrial outlet, you can get single phase power of up to 32A (7360W), but I doubt most electricians would install that for you at a house.
    - nwh 14y ago
      Oddly enough, I've got a 32A socket hooked up to a water pump. I'm not entirely sure why the electrician installed in, there's no way the pump draws more than an ampere or two. Thanks for explaining the 240/230v difference, I'd always wondered why it existed.
      - Tuna-Fish 14y ago
        And some parts of EU still actually have 220V. There's no major practical difference between 220V/230V/240V, it's just that different parts of the world came up with slightly different standards. As standardization has progressed, now all of EU is on a nominal 230V ± 6% 50Hz -- in practice the countries are still supplying their old voltages. 230 is presently 220 in Hungary and 240 in UK. Since both are within the mandated 6%, this doesn't cause problems. Eventually, as parts of the grid are serviced and replaced, it will be transformed into unified 230V.
        glogla 14y ago
        Also lot of electronics nowadays uses switched-mode supply so it doesn't really matter all that much.
    - plaguuuuuu 14y ago
      Seriously? Which machine is that?
dredmorbius 14y ago
Per Tesla's own charging estimates 110v/12A is good for about 5 miles/hour of charging. http://www.teslamotors.com/charging#/outlet http://www.teslamotors.com/charging#/outlet That's not particularly meaningful. 60 hours to a full 85kWh charge.
- jaggederest 14y ago
  That would be fine for me, but my usage is not most people's usage.
  - dredmorbius 14y ago
    It's fine for a moderate commute where you're driving less than 60 miles or so (assuming a 12 hour overnight charge). More so if you've got access to higher-output charging at another location. The case in the NY Times Tesla review is specifically for a long-range winter road trip, for which Superchargers are pretty much essential.

iyulaev 14y ago

Absolutely right. I was using 120V as shorthand for "the 120V/20A circuit that we're all used to."

zanny 14y ago
I don't think saying "120v isn't enough, you need to rewire your entire house" is really accurate either. Most water heaters, stoves, and some central heaters run off a merged breaker for 240v. You can easily use one of those lines for the car if you don't plan on taxing the thing the entire time (though I figure if you have 50k for a car you have 1k to add an extra circuit and wire your garage up for it). Also, 240v cars makes so much more sense in a world where 99% of people use 240v outlets, and in the US you can just oscillate two 120v's and get a usually-good-enough 240v signal.
iyulaev 14y ago
I don't think saying "120v isn't enough, you need to rewire your entire house" is really accurate either. Most water heaters, stoves, and some central heaters run off a merged breaker for 240v. You can easily use one of those lines for the car if you don't plan on taxing the thing the entire time (though I figure if you have 50k for a car you have 1k to add an extra circuit and wire your garage up for it). Yes, although at least in my view part of the selling point is that we have plugs everywhere, so you have electricity anywhere right? Well, hunting around for a 240V plug is a big harder than 120V. Also, even though 99% (???) of the world is on 240V, I think the current rating on those circuits still limits power to around 2kW sustained.
- stephen_g 14y ago
  I'm in Australia, and our power supply is 230V AC (+/- 6%) (240V was the standard before 2000, but is still within the acceptable limits). Most power outlets are 10A (max ~2300W) but I also have two 15A sockets in my house for the air conditioners (3450W - I also use one to power my coffee machine, which pulls 3200W when warming up!), and could theoretically get a 20A socket (4600W) installed. With an industrial outlet, you can get single phase power of up to 32A (7360W), but I doubt most electricians would install that for you at a house.
  - nwh 14y ago
    Oddly enough, I've got a 32A socket hooked up to a water pump. I'm not entirely sure why the electrician installed in, there's no way the pump draws more than an ampere or two. Thanks for explaining the 240/230v difference, I'd always wondered why it existed.
    - Tuna-Fish 14y ago
      And some parts of EU still actually have 220V. There's no major practical difference between 220V/230V/240V, it's just that different parts of the world came up with slightly different standards. As standardization has progressed, now all of EU is on a nominal 230V ± 6% 50Hz -- in practice the countries are still supplying their old voltages. 230 is presently 220 in Hungary and 240 in UK. Since both are within the mandated 6%, this doesn't cause problems. Eventually, as parts of the grid are serviced and replaced, it will be transformed into unified 230V.
      - glogla 14y ago
        Also lot of electronics nowadays uses switched-mode supply so it doesn't really matter all that much.
  - plaguuuuuu 14y ago
    Seriously? Which machine is that?

dredmorbius 14y ago

Per Tesla's own charging estimates 110v/12A is good for about 5 miles/hour of charging. http://www.teslamotors.com/charging#/outlet http://www.teslamotors.com/charging#/outlet That's not particularly meaningful. 60 hours to a full 85kWh charge.

jaggederest 14y ago
That would be fine for me, but my usage is not most people's usage.
- dredmorbius 14y ago
  It's fine for a moderate commute where you're driving less than 60 miles or so (assuming a 12 hour overnight charge). More so if you've got access to higher-output charging at another location. The case in the NY Times Tesla review is specifically for a long-range winter road trip, for which Superchargers are pretty much essential.