9 ms·

The article says that today a battery pack the size of a backpack and that weighs about 40kg, can power a house for a day. Is that really so? Would that be a no

• tyingq 6y ago
  A Tesla Powerwall 2 weighs 114.0 kg and provides 13.5 kWh. Average US household electricity consumption is 877 kWh/month, which would be 29kWh/day. Either they mean a very efficient/small house, or homeowners with unusually frugal habits. Edit: Average UK household electricity consumption appears to be around 10kWh/day.
  • Someone 6y ago
    Or houses not in the USA. http://shrinkthatfootprint.com/average-household-electricity-consumption http://shrinkthatfootprint.com/average-household-electricity...: “The average American or Canadian household in 2010 used about twenty times more than the typical Nigerian household, and two to three times more than a typical European home”
    • umvi 6y ago
      Why is that? Is it because North Americans use electricity for cooking and heating whereas other countries use gas for that?
      • tyingq 6y ago
        I suspect big houses, poor insulation, air conditioning, and gluttony. Most of the US houses I've been in use either gas or fuel oil for heating.
        • galangalalgol 6y ago
          We have lots of elctric furnaces or heat pumps in the southern and western states where winters are milder. The air conditioning is the real usage. The insulation in new homes is good, but the insulation to keep heat out needs to be in walls as much as ceilings which is harder to retrofit. Modern AC systems help quite a lot and keeping heat away from ac ducting in the attic by insulating them amd adding roof vents and radiant barrier to keep the attic cool. Lighter colors so your south facing wall doesn't fry eggs (literally) also help.
      • fwsgonzo 6y ago
        Probably due to differences in standards, like wall isolation (I don't know the english terms). My house has 25cm isolation in the walls and 40cm isolation under the roof. I also have 3-layer windows and a thick metal door. The ventilation system is isolated and the air heat is reused to save electricity. This is for a 260sqm house.
      • geoduck14 6y ago
        It's cause we're #1!!! /s
      • nightski 6y ago
        We average 400-500 in the spring, fall, and winter. In the summer with AC however we'll double that. We are in a northern climate, I have to imagine in the south it gets pretty spendy for AC.
      • ajuc 6y ago
        Air conditioning isn't needed in many EU countries except for a few days a year (so it's not worth to even install it in private homes, modern offices mostly have them though for some reason). Also depending on the country few people use cloth driers - you just hang your clothes on a cable and let them dry by themselves. Houses in colder parts of EU are also usually better isolated than in US ([1] that's a typical Polish house for example), and more people live in flats in blocks instead of independent houses (so heat loses are vastly reduced because you only have 1 or 2 outdoors walls). Homes are also simply bigger in US. Average home size (including flats) in my country is a little over 70 square meters. It's probably bigger in western Europe but not by that much. Also big houses usually have 2/3 stories instead of being very "wide". And electric heating/cooking isn't very popular, but I think that depends on the country. It all goes back to electricity prices - in Poland in 1980s most houses had no isolation, everybody heated with coal which had fixed (and very low) prices. Then communism ended, prices were free to change with the market, some taxes were introduced, and suddenly everybody isolated their houses in like 10 years. Otherwise you burned money like crazy. [1] https://s3.eu-central-1.amazonaws.com/pressland-cms/cache/__original__/tl/20503051-https-bi.jpeg https://s3.eu-central-1.amazonaws.com/pressland-cms/cache/__...
        • baybal2 6y ago
          > ([1] that's a typical Polish house for example), I believe a typical Polish "house" will be an apartment.
          • ajuc 6y ago
            42% of Poles live in apartaments. It was slightly above 50% several years ago.
        • thesteamboat 6y ago
          Sorry to nitpick, but I assume you mean EU houses are better insulated than those in the US, rather than isolated.
          • ajuc 6y ago
      • fulafel 6y ago
        US housing is very roomy, often features AC and poor insulation, and electricity is cheap and avergae incomes are high.
      • cwhiz 6y ago
        Same reason most Americans are poor. Inability to prioritize long term goals over immediate gains. Save $50 today, but spend $500 more over the next decade.
  • 300africans 6y ago
    Here in Burkina faso, I use between 5 and 12kwh per day with air con some months taking it close to 15kwh. If the price keeps coming down and with some solar installation, one can leave the grid in a couple of years time
    • marcosdumay 6y ago
      I imagine most of the aircon energy usage coincides with the times of peak photovoltaic generation. So if you calculate by total energy consumption, you'll overestimate things by a huge margin.
      • Armisael16 6y ago
        You can imagine that, but it isn’t true. AC usage is relatively low in the middle of the day because people let their houses warm up while their at work. It jumps at the end of the workday.
        • nicoburns 6y ago
          > AC usage is relatively low in the middle of the day because people let their houses warm up while their at work Presumably if electricity was free during th day and expensive at night, that habit would change rapdily.
        • _JamesA_ 6y ago
          Is that still true in the work from home post covid era?
    • baybal2 6y ago
      How is life in Burkina Faso?
  • ghaff 6y ago
    It also looks like a Powerwall 2 costs about $7,500 plus about another $5K for installation. I use about 20kWh per day--I have a somewhat smaller house--and vaguely looked into whole house batteries a few months back and concluded they would only make sense if I had it wired into just a few critical systems like my furnace. But, at the end of the day, I should still just get a propane-fueled generator at this point if I ever got anything. So $2K for a battery that can power a house for a day seems almost an order of magnitude off if they literally mean power an entire normal house.
    • quickthrowman 6y ago
      > But, at the end of the day, I should still just get a propane-fueled generator at this point if I ever got anything. Yes, a propane or natural gas generator is a lot more flexible/higher capacity
  • dv_dt 6y ago
    It’s enough for the twilight evening usage for a household when paired with a solar system.
  • adrianmonk 6y ago
    Your point still stands, but there's probably some small correction factor necessary since the article seems to be talking about the weight of the cells only. Although I'd bet the weight of the cells does make up the majority of the mass of a Powerwall, other components might have significant weight. From some quick, cursory research, it seems to have a metal frame/cover and apparently has some kind of liquid cooling. (Also, minimizing weight for a Powerwall seems less important than for an EV.)
  • natch 6y ago
    The average US house is not the average house, nor is it representative of normal in the world we live in, which happens to dwarf the US by a factor of roughly 25.
    • tyingq 6y ago
      I don't assume they mean something smaller than a factor of 25 either. 1.2kWh would be substantially less than 40kg.
      • kragen 6y ago
        No, no, the world is 25 times bigger than the US, by population. So it's ridiculous to equate houses with US houses, especially when reading a British publication.
        • tyingq 6y ago
          The article uses US dollars quite a lot. That's why I posted US stats, marked as such. I did update it with a UK average as well. Also, FWIW, the North American edition of the Economist accounts for more than half the readers. UK readers are less than 20% of the total.
          • natch 6y ago
            Kragen was right, I was talking about the size of the world. The US is not representative of average or normal. Nor is the UK. And UK publications, due perhaps to colonial history, tend to take a more global view so I would not assume their notion of an average house is centered on the UK either.
            • tyingq 6y ago
              Neither is air conditioning representative of the world, or people with a "house" that have $2k to spend on a 40kg lithium battery plus more on the other stuff like inverters, frames, installation. But all are clearly noted in the article as part of the target audience.
  • sgt 6y ago
    South Africa here. Our house uses about 20 kWh a day during the summer, with some minor AC usage in one of the rooms when needed. During the winter probably about 30kWh, and that excludes extra costs like wood for fireplace. My house is fully insulated and all windows are double glazed, so that keeps energy usage more efficient. I also have a solar heater (aka "geyser") which lowers energy costs even more. So with that in mind, I really can't believe they're using less than this in Europe...
    • bobthepanda 6y ago
      They might be just using less electricity but other means to generate their needs. I've heard that the EU has a lot more district heating (which wouldn't show up in an electricity bill, AFAIK) and I'd imagine a fair deal of older buildings have a boiler using oil or gas or something else to burn. AC is also just not very prevalent.
      • nicoburns 6y ago
        > I'd imagine a fair deal of older buildings have a boiler using oil or gas or something else to burn. In the UK gas boilers are common even in newbuild homes. I don't know a single person with AC (though it's common in offices).
    • brucehoult 6y ago
      Far north New Zealand, 4 bedroom house, no insulation, no double glazing, electric hot water and cooking. 9-10 kWh/day October-May, ~18 kWh/day June-September (dehumidifier). Wood burner (about US$150/winter) when the heat from the dehumidifier isn't enough to maintain 20 C.
      • sjwright 6y ago
        Remarkable. I’m in Sydney, my house sounds similar by description but I have gas hot water and stovetop. My house uses over 5 kWh/day for ambient/idle power alone.
        • 6y ago
  • petra 6y ago
    So 29kWH/day. Say you get half of that from your solar panels at sunrise. 13.9kWh is almost the other half.
• gok 6y ago
  At best it would store about 8kWh, so... it would have to be a pretty efficient house.
• Phenomenit 6y ago
  I think that depends on how much heating/cooling is being used.it should be enough for just lights and devices.
• Tade0 6y ago
  40kg translates to 4-9kWh depending on the chemistry, meanwhile houses in the UK draw around 3kWh/day averaged over a year so unless a house is woefully inefficient, it checks out.
  • labawi 6y ago
    > Average US household .. 29kWh/day > houses in the UK .. 3kWh/day Seems believable from what I've heard.
    • turbinerneiter 6y ago
      I think in the US it's common to heat and cool badly insulated houses with electricity, whereas in europe almost nobody cools, heat comes from other sources and insulation is taking way more seriously, especially for anything built recently. The best way to reduce your energy bill (whichever source) is to live in the right climate zone I guess.
      • ghaff 6y ago
        Electric heat isn't super common, especially in standalone houses, in areas where you need a lot of heat in the US. I don't know the numbers off the top of my head but electricity costs a lot more than gas or oil. You're right about the AC but I still use 20 kWh even with no AC (and no electric heat).
        • turbinerneiter 6y ago
          Thanks for the insight. I vaguely remembered that people run the ac in reverse for heat, but that is probably only in paces that almost need no heating. Do you know why you use that much? Do you heat your water with electricity? Fridge, freezer, tv, WiFi, Desktop PC, charging phones and laptop, ligths.
          • ncallaway 6y ago
            - AC is a very common consumer of large amounts of electricity (depending on the region, many regions will have almost no AC while other regions will have it in every building running almost constantly) - Electrical heat is not the most common form of heating, but it's been growing a lot and is also a big consumer when it is used - Laundry Washer/Dryer are pretty large consumers (mostly the dryer) - Water heaters are often electrical - Electrical ovens and stove ranges are pretty common, which can pull quite a bit depending on how much use they receive - Microwaves pull a bit, but not huge
• f6v 6y ago
  Very much depends on the home. Tesla Powerwall 2 seems to be 13.5 kWh at 114 kg. Energy consumption can be anything from 30 to 40[1]. So one Powerwall 2 unit probably won't get you through the day if you use that much. [1] https://www.eia.gov/energyexplained/use-of-energy/electricity-use-in-homes.php https://www.eia.gov/energyexplained/use-of-energy/electricit...
  • natch 6y ago
    Getting you through the day is not really the point though. The point is 1) shifting some consumption during peak hours off of peak rates and 2) having backup to get you through a limited outage, not necessarily at your full normal consumption level but without having to be in the dark / without internet / without phone and possibly car charging. Nobody should evaluate this by whether one battery pack by itself provides all the energy anyone needs for everything with no limits. It’s one component with several good use cases.
    • spockz 6y ago
      I’m not sure about regulations in the US but in The Netherlands you cannot just attach a battery and think you are independent of the grid. To protect the net and people working on the net, power sources behind the meter must disengage when the net/mains power drops. This effectively disables your independence plan. If you want to be independent you have to get some expensive mechanism installed that will decouple your house from the net in case of net failure and bring it back when the mains is up again. And you need get it certified periodically. So unless you have enough generation to completely decouple from the net you are not really independent or it will cost you.
      • kragen 6y ago
        This is correct in the US as well, except that I'm not sure about the periodic certification thing.
      • jccooper 6y ago
        Transfer switches are standard for pretty much any generator setup. An automatic one is a bit more expensive, but hardly a deal breaker.
• deleted 6y ago
  [deleted]
• turtlebits 6y ago
  The wording in the article isn't great, but they are referring to the power consumption for a household in 1990.
• kragen 6y ago
  https://en.wikipedia.org/wiki/Energy_density_Extended_Reference_Table https://en.wikipedia.org/wiki/Energy_density_Extended_Refere... lists "battery, Lithium ion" as 0.46–0.72 MJ/kg. : user@host:~; units 2529 units, 72 prefixes, 56 nonlinear units You have: 40 kg * 0.6 MJ/kg You want: MJ * 24 / 0.041666667 (The 13.5 kWh in 114 kg tyingq cites for a Powerwall 2 in https://news.ycombinator.com/item?id=26682770 https://news.ycombinator.com/item?id=26682770 works out to 0.43 MJ/kg, which includes some power electronics as well as the batteries themselves. The US$12500 price ghaff cites in https://news.ycombinator.com/item?id=26682837 https://news.ycombinator.com/item?id=26682837 works out to under 4 kJ/US$, or US$925/kWh, which is a terribly high price even for lithium-ion.) 24 MJ would be 1 MJ/hour for 24 hours, or 3 MJ/hour for 8 hours, about 300 or 800 watts, respectively. Some houses use much more than that; others use much less. If you're looking at your electric bill, 500 watts would be about 370 kWh per month: You have: 500 watts * 1 month You want: kWh * 365.2422 / 0.0027379093 40 kg of lithium-ion batteries are indeed roughly the size of a backpack (≈20 liters), though I wouldn't call it a small backpack. Around here, the retail price for the batteries would probably be closer to US$2400 retail than the less than US$2000 they cite, but that's not an error in their calculations; it's just that they're using a lower price of US$140/kWh. The article claims that in the early 01990s this quantity of batteries would have cost US$75k. I'm pretty sure this is wrong. This quantity of lithium-ion batteries might have cost US$75k, but even today lead-acid batteries cost half what lithium-ion batteries do. I don't think the price of lead-acid batteries has changed that much over the last 25 or even 50 years, though admittedly I don't have any 30-year-old battery catalogs to check pricing in. Lithium-ion batteries in the 01990s would have weighed only a little more than lithium-ion batteries today, so it looks like they're using the pricing of lithium-ion batteries and the weight of lead-acid batteries. If you're powering your house from batteries, you should probably do it with lead-acid batteries, not lithium-ion batteries. The big disadvantage of lead-acid batteries is that they weigh roughly three times what lithium-ion batteries do (per joule), so lead-acid electric cars had roughly a third the range of lithium-ion electric cars. But the weight is not enough to matter for a house. There is enough lithium in Earth's crust to power the world economy through the night. There is, I think, not enough lead. So although lead is currently cheaper, lithium is more scalable. Other less developed candidate options include sodium batteries and aluminum fuel cells. Nickel-iron batteries might be even cheaper, though I'm not sure, and they're definitely more scalable. Nobody sells them anymore, though lots of telecom centers still run on them. It's unfortunate that the article cites a power capacity, "1.2 gigawatts-worth of storage", but not an energy capacity, for the US's utility-scale storage rampup last year. 1.2 gigawatts for five minutes would be 100 MWh, in the quaint units used in the energy markets; 1.2 gigawatts for 12 hours would be 14'400 MWh. There is a very significant difference between these; one requires 144 times as much battery behind it than the other. By contrast, the difference between 100 MWh over 5 minutes (1.2 gigawatts) and 100 MWh over 12 hours (0.008 gigawatts) is mostly a matter of what shape the batteries are and how much active cooling is needed. One wonders if this is not simply an error because the author did not know the difference between gigawatts and gigawatt-hours.
• shoo 6y ago
  Another anecdote: I rent a 50m^2 apartment. Electricity consumption for the apartment, averaged over trailing 12 months, is 4.5 kWh / day. This excludes: energy for stove top/oven (natural gas) and energy for hot water (paid for as part of rent, cannot see the details). Consumption for two people, including one person working from home full time. Relatively modern apartment that is warm enough in winter without active heating. This will not be representative of energy usage in houses, larger apartments with many exterior sides & lots of exposed glass. edit: house prior to that was an older 100 m^2 semi-detached house with much worse insulation. Similar setup with natural gas for cooking & hot water. Annual electricity consumption was 1750 kWh / year so about 4.8 kWh / day on average, for two people. Not so different to the current situation. Curious. From memory we ran the air conditioner on a few days in summer and electric heating in the depths of winter. From memory the house was somewhat unpleasantly cold some of the time so perhaps we tended to put on warm clothing rather than try to heat the whole place.
  • kccqzy 6y ago
    That sounds reasonable. My house is about twice your size and so is my electricity consumption (8.8 kWh/day last billing cycle). Also doesn't exclude stove/oven/hot water as these are all powered by natural gas. I was shocked by a few other comments saying 30 kWh/day. Is it because they use electricity to cook and heat water?
• kumarvvr 6y ago
  A tesla 2 powerwall, weighs about 120 kg and holds about 14 kWh of power. In India, the average household has a 2.5 kW Peak Power meter and usually, about 10 kWh per day is consumed. So, not exactly a back-pack, but yeah. The average individual house in India, is constructed in a plot of about 200 Square Yards. Usually available roof space is about 1000 sft. Assuming no shadows or high rises in the vicinity (80% of homes have good sunshine even in dense cities), this area is sufficient for about 5 kW of installed capacity. Most of the deccan plateau gets about 6 hours of good sunshine year-round. So that translates to about 30 kWh of power generation capability. So, a 3 kW installed capacity, with 1 powerwall will be sufficient to power an average household for most of the year. Of course, this does not take into account usage of ACs (a fast increasing power consumption category in India) However, it costs about Rs. 100,000 for 1 kW of installed capacity (including inverter and grid connected meter, no batteries) For 5 kW, that is 500,000 Rs. (about 7000 USD) of investment. Average annual salary of an Indian household in an urban area is about 15000 USD. About half of that in rural areas. If there are good financing options and grid connected reverse selling meters (they are being encouraged by many local and state governments), there could be a revolution in installed solar capacity and utilization.