7 ms·

> Converting a gas appliance to a heat pump, for example, would draw 4 to 6 kW, while an L2 charger for EVs would be 12 to 14 kW. A This article has an issue w

> Converting a gas appliance to a heat pump, for example, would draw 4 to 6 kW, while an L2 charger for EVs would be 12 to 14 kW. A This article has an issue with numbers here clearly. A heat pump isn’t really going to consume more electricity than the AC it replaces (and hopefully it is more efficient than the cool-only-AC it replaces as well so electricity uses decreases in the summer). For electric cars, no-one needs 48A (11.5kw) charging (unless you bought a hummer EV and then you’re an idiot). The city can start denying permits for charging at more than 24-32A unless you have enough battery storage to cover it up. Palo Alto also does not have TOU plans, and no demand charges.

falcolas 4y ago
FWIW, if you use 2.4kw charging (Level 1, typical for a household) , it may take multiple days to recharge your 80kwh battery. Charging overnight, for example, it would require three full nights to get back a complete charge. While this wouldn't be a problem for most folks, there are definitely many who could easily outstrip the power provided by a Level 1 charger (in my area, construction workers who are driving around 100 miles per day to their worksite is an example). Also, you need a minimum of level 2 charging to support long distance travel by road, where a full battery can be consumed in about 3 hours of highway driving.
- _ea1k 4y ago
  Did you reply to the wrong comment? OP said nothing about L1?
  - falcolas 4y ago
    Nope, right comment. > or electric cars, no-one needs 48A (11.5kw) charging refers to L2 DC fast charging. The next level down (which is implied by "nobody needs L2") is L1 charging, which is done on a household 120V or 220V circuit. In other words, if you don't supply L2 (and L3) DC fast charging for customers who need it, EVs will never replace ICE.
    - bryanlarsen 4y ago
      No, he's saying that 24-32A charging is enough. > The city can start denying permits for charging at more than 24-32A unless you have enough battery storage to cover it up.
      - falcolas 4y ago
        32A at 240V (the standard for DC fast charging) is ~8kw, so you'd still be looking at 10 hours for a battery charge. Sufficient for my construction workers, insufficient for supporting long distance driving.
        bryanlarsen 4y ago
        I think we can agree that anybody who averages more than 400 miles a day is going to need more than 24A charging. Commercial drivers should be using commercial facilities, not residential ones.
        falcolas 4y ago
        Anybody taking a road trip falls into this category. You couldn't drive from San Francisco to LA without access to L3 charging.
        bryanlarsen 4y ago
        Both 24A and 48A charging are both similarly insufficient for a road trip, so I'm unsure how your comment relates to thatfrenchguy's original comment.
        falcolas 4y ago
        His original comment says no L3 capable charging should be allowed, with the only exception requiring a huge investment in expensive battery storage (Lithium Ion packs cost around $200 per kWh, built at a MWh scale) - something unprecedented with gasoline infrastructure.
_ea1k 4y ago
TBH, 11.5kw would be enough for most people with a Hummer EV too. It'd still gain ~50% overnight. It could keep up with a 100 mile commute.
mikeyouse 4y ago
They're specifically talking about replacing gas appliances with heat pumps -- e.g. heaters. A moderate sized 3-ton unit uses around 5kw to heat on cooler days where a gas furnace might use 0.1kw to turn the blower motor. I live in a weird house that has 3 gas furnaces but only one of of the furnaces has AC attached at the moment. I'm going to swap out two of the three for ducted heat pumps, so my peak electrical load in both seasons will increase by roughly 5kw. Replacing the third furnace (with the AC) would surely reduce the cooling electrical load since it's old and outdated, but would add another few kw to my winter heating load if I were to do so.
theli0nheart 4y ago
> For electric cars, no-one needs 48A (11.5kw) charging (unless you bought a hummer EV and then you’re an idiot). The city can start denying permits for charging at more than 24-32A unless you have enough battery storage to cover it up. You're wrong about this. We frequently take day trips that are about an hour each way from home, and without the L2 we would get dangerously low after another day of commuter driving. As a co-poster noted, standard chargers will take days to recharge. Ours does about 6 miles of charge / hour, whereas the L2 does about 30 miles of charge / hour.
- bryanlarsen 4y ago
  What kind of vehicle & miles do you have where 24A charging isn't enough?
  - jwcooper 4y ago
    A 7.2kw level 2 charger using 32A is pretty standard, 24A would be slower than I'd want for daily use, and I own an older Leaf. Even at 32A, it's slow when you need to charge quick for any reason (top off for afternoon errands, etc).
    - bryanlarsen 4y ago
      I have a 320 mile range, so I never need to top off for afternoon errands. Naively you'd think that cars with a larger battery would be more likely to need a level 2 charger since it takes so much longer to charge a large battery on L1 than it does a small battery. But in fact it's often the opposite -- a big battery means you only need enough charger to handle an average day rather than a peak day.
- judge2020 4y ago
  Which is why the OP includes 32A=7.7kw charging, which is what Tesla's get. OP is only really against insane installations where you charge at 48A=11.5kw, that's the capacity of 1.5 Teslas, and is only really necessary when you're running a horribly inefficient Hummer EV (200 kwh battery getting 350 miles EPA range means it's operating about 600 wh/mile or 1.6 miles per kwh, twice the energy usage of a Model X).
michaelt 4y ago
Your quote from the article explicitly says converting a gas appliance (e.g. a water heater) to electricity increases electricity consumption, which is obviously true so I'm not sure why you take issue with the article?
ec109685 4y ago
EVs almost never need 48A charging, but for times when they do, it’s what makes EV only households practical. The answer isn’t to ban high AMP L2 chargers but instruct cars to only use high amp when lower amp charging isn’t sufficient. For most users who do home charging, they leave them plugged in for 10+ hours at night and drive nowhere near their battery’s capacity, so trickle charge them each night, ensuring car is ready at their scheduled departure time.

falcolas 4y ago

FWIW, if you use 2.4kw charging (Level 1, typical for a household) , it may take multiple days to recharge your 80kwh battery. Charging overnight, for example, it would require three full nights to get back a complete charge. While this wouldn't be a problem for most folks, there are definitely many who could easily outstrip the power provided by a Level 1 charger (in my area, construction workers who are driving around 100 miles per day to their worksite is an example). Also, you need a minimum of level 2 charging to support long distance travel by road, where a full battery can be consumed in about 3 hours of highway driving.

_ea1k 4y ago
Did you reply to the wrong comment? OP said nothing about L1?
- falcolas 4y ago
  Nope, right comment. > or electric cars, no-one needs 48A (11.5kw) charging refers to L2 DC fast charging. The next level down (which is implied by "nobody needs L2") is L1 charging, which is done on a household 120V or 220V circuit. In other words, if you don't supply L2 (and L3) DC fast charging for customers who need it, EVs will never replace ICE.
  - bryanlarsen 4y ago
    No, he's saying that 24-32A charging is enough. > The city can start denying permits for charging at more than 24-32A unless you have enough battery storage to cover it up.
    - falcolas 4y ago
      32A at 240V (the standard for DC fast charging) is ~8kw, so you'd still be looking at 10 hours for a battery charge. Sufficient for my construction workers, insufficient for supporting long distance driving.
      - bryanlarsen 4y ago
        I think we can agree that anybody who averages more than 400 miles a day is going to need more than 24A charging. Commercial drivers should be using commercial facilities, not residential ones.
        falcolas 4y ago
        Anybody taking a road trip falls into this category. You couldn't drive from San Francisco to LA without access to L3 charging.
        bryanlarsen 4y ago
        Both 24A and 48A charging are both similarly insufficient for a road trip, so I'm unsure how your comment relates to thatfrenchguy's original comment.
        falcolas 4y ago
        His original comment says no L3 capable charging should be allowed, with the only exception requiring a huge investment in expensive battery storage (Lithium Ion packs cost around $200 per kWh, built at a MWh scale) - something unprecedented with gasoline infrastructure.

_ea1k 4y ago

TBH, 11.5kw would be enough for most people with a Hummer EV too. It'd still gain ~50% overnight. It could keep up with a 100 mile commute.

mikeyouse 4y ago

They're specifically talking about replacing gas appliances with heat pumps -- e.g. heaters. A moderate sized 3-ton unit uses around 5kw to heat on cooler days where a gas furnace might use 0.1kw to turn the blower motor. I live in a weird house that has 3 gas furnaces but only one of of the furnaces has AC attached at the moment. I'm going to swap out two of the three for ducted heat pumps, so my peak electrical load in both seasons will increase by roughly 5kw. Replacing the third furnace (with the AC) would surely reduce the cooling electrical load since it's old and outdated, but would add another few kw to my winter heating load if I were to do so.

theli0nheart 4y ago

> For electric cars, no-one needs 48A (11.5kw) charging (unless you bought a hummer EV and then you’re an idiot). The city can start denying permits for charging at more than 24-32A unless you have enough battery storage to cover it up. You're wrong about this. We frequently take day trips that are about an hour each way from home, and without the L2 we would get dangerously low after another day of commuter driving. As a co-poster noted, standard chargers will take days to recharge. Ours does about 6 miles of charge / hour, whereas the L2 does about 30 miles of charge / hour.

bryanlarsen 4y ago
What kind of vehicle & miles do you have where 24A charging isn't enough?
- jwcooper 4y ago
  A 7.2kw level 2 charger using 32A is pretty standard, 24A would be slower than I'd want for daily use, and I own an older Leaf. Even at 32A, it's slow when you need to charge quick for any reason (top off for afternoon errands, etc).
  - bryanlarsen 4y ago
    I have a 320 mile range, so I never need to top off for afternoon errands. Naively you'd think that cars with a larger battery would be more likely to need a level 2 charger since it takes so much longer to charge a large battery on L1 than it does a small battery. But in fact it's often the opposite -- a big battery means you only need enough charger to handle an average day rather than a peak day.
judge2020 4y ago
Which is why the OP includes 32A=7.7kw charging, which is what Tesla's get. OP is only really against insane installations where you charge at 48A=11.5kw, that's the capacity of 1.5 Teslas, and is only really necessary when you're running a horribly inefficient Hummer EV (200 kwh battery getting 350 miles EPA range means it's operating about 600 wh/mile or 1.6 miles per kwh, twice the energy usage of a Model X).

michaelt 4y ago

Your quote from the article explicitly says converting a gas appliance (e.g. a water heater) to electricity increases electricity consumption, which is obviously true so I'm not sure why you take issue with the article?

ec109685 4y ago

EVs almost never need 48A charging, but for times when they do, it’s what makes EV only households practical. The answer isn’t to ban high AMP L2 chargers but instruct cars to only use high amp when lower amp charging isn’t sufficient. For most users who do home charging, they leave them plugged in for 10+ hours at night and drive nowhere near their battery’s capacity, so trickle charge them each night, ensuring car is ready at their scheduled departure time.