Buy Your Friends Batteries

(domenkozar.com)

61 points | by domenkozar an hour ago ago

59 comments

  • Retr0id an hour ago

    > Create a battery birthday club. Buy each friend a battery on their birthday until everyone has one.

    At that point, wouldn't it be easier if everyone just bought their own? And then whoever has the latest birthday doesn't have to wait a year to get theirs.

    • cbarnes99 an hour ago

      I think the point is that breaking it up makes the cost more palatable. It's also easier to convince people to spend a bit of money for people they care about than a bunch for themselves that they don't strictly need. People also often struggle to think of gift ideas for birthdays.

      • deepfriedbits 10 minutes ago

        True, but you're still buying an entire battery yourself in the course of a calendar year.

        I love the spirit behind this but it's strange advice. I consider myself lucky to have a healthy roster of adult friends, and I still think getting 16 of them to spend significant money on each other's birthday would be a big ask to pull off.

    • oytis an hour ago

      But then you still have to buy birthday presents on top of that

      • Retr0id 43 minutes ago

        If everyone's giving everyone the same gift, it's not really a "gift" any more, more of a p2p buy-now-pay-later arrangement (which isn't a terrible idea, but it's suboptimal for those with later bithdays).

        • blitzar 39 minutes ago

          Might as well just have an annual theme and try to negotiate a bulk discount.

        • ruined 14 minutes ago

          it's simple. if i were part of an economy, we would all just act rationally. that way everything would be efficient

        • cactusplant7374 25 minutes ago

          Not everything needs to be optimized. Probably only rich people would engage in such a scheme anyway.

          • Retr0id 24 minutes ago

            The whole premise here is cost optimization.

    • domenkozar an hour ago

      That's step one, next is your friends.

    • benj111 28 minutes ago

      No. This is how building societies work.

      You may not have £100,000 but if you get 1000 people with £100 then you can buy a house.

      Obviously the birthday system doesnt address the interest, but I'm sure your friends would be ok paying interest right?

      • rcktmrtn a minute ago

        I think building societies "bid" to decide who gets to go first. Whoever is willing to take the smallest loan/pay back fastest gets preference.

        Reinventing building societies seems very cool to me -- it's a little more nuanced than the birthday thing, but it's a system that can work with assets that generate value.

    • toomuchtodo 30 minutes ago

      It is like an energy storage cost cutting rotating potluck. blitzar mentions bulk buying in a comment, which is a great idea to drive down cost. Not sure what the EU version of that looks like, the US versions are:

      https://solarunitedneighbors.org/

      https://www.brightsaver.org/

      Europe has quote a bit of renewable generation currently that is curtailing or otherwise going unused, and needs all of the battery energy storage it can get (residential, commercial, utility scale) to convert curtailment into realized clean energy offsetting potential fossil energy usage (gas and coal).

      Solar Power Is So Big in Europe That Electricity Is Being Wasted - https://www.bloomberg.com/news/articles/2026-05-13/europe-so... | https://archive.today/nAdiA - May 12th, 2026

      > Hundreds of millions of solar panels have been installed in Europe, turning solar into the region's biggest source of power during summer months, but the system around it hasn't kept up. A record amount of electricity is being wasted because grids can't handle the surge in output, with about 40 terawatt-hours of electricity expected to go to waste in the coming months. The glut of solar power is pushing power prices deep below zero during peak solar hours, eroding returns for producers and forcing them to shut down plants, with consumers potentially paying twice for the subsidies and compensation.

  • isoprophlex an hour ago

    > You are also safer during a power outage. The STREAM 5000 provides up to 3 kW of off-grid output. Keep essential devices on its backup output and reserve some battery capacity, and your refrigerator, lights, router, and laptop can keep running when the grid goes down. An ordinary grid connection does not back up the whole house automatically; the backup output must be configured correctly.

    Being able to cut over your entire house from grid power to a battery requires an invasive, expensive change to most connections. I wish people would stop breathlessly promoting batteries (which are good! we need decentralized storage!) because "you can use them to run your fridge, router, etc". Yes you can, but for almost all consumers it's an order of magnitude more effort and cash compared to just buying and plugging in a battery.

    • ssl-3 20 minutes ago

      And the proposed battery solution only works at up to 3kW. My electric range uses more than that, and my water heater, clothes dryer, and aircon each come close.

      And, sure: I can get by very well with refrigeration, networking, computing and/or TV, and lights during a power outage. But those loads need to be segregated, or it just doesn't work. That adds more expense.

      And since those segregated loads don't even come anywhere near 3kW, it isn't clear to me how I'm to be maximizing my local use of surplus power events.

      There are grid-interactive battery solutions from companies like EG4 that can go betwixt the entire house and its grid connection, but this isn't it.

    • Aachen 41 minutes ago

      Not necessarily the point. If it provides a normal wall outlet I'm happy to plug essentials around for the one time per 1-2 decades this happens for longer than 4 hours and the fridge/freezer/laptop needs a boost

      • EvanAnderson 33 minutes ago

        As long as you're not opening the fridge / freezer during the outage (and you have sufficient thermal mass of food in it) you don't need to worry about "boosting" it during a power outage of only 4 hours. I don't recall the rule of thumb off the top of my head, but for at least 6 hours I'd expect the contents of normal fridge / freezer to be just fine (as long as there's thermal mass there).

        • jonathanlydall 26 minutes ago

          Can confirm from years of load shedding in the past in South Africa where my area had 4 hour outages.

          That duration was tough for various reasons, but fridge and freezer were not really an issue.

          I was very happy when they changed to 2 hour outages (albeit twice as many), and then even happier with not having load shedding for about 2 years now.

      • coldpie 14 minutes ago

        I dunno. TBH I'd rather just let the food go bad than bother with the expense and hassle of having a battery and keeping it charged. I guess other locations may have less reliable grids than I do, but I've only experienced one power outage that lasted so long[1] that our food went off in my entire 40 years living in the Twin Cities area.

        [1] About 96 hours, major storm took down a ton of trees through the whole metro area that took days to clear.

      • rtkwe 20 minutes ago

        The issue there is the plug would be on the battery which you're unlikely to have mounted in a convenient location for things like your main fridge, router, and computer. For me all 3 of those are pretty far away from the most likely places I'd put a battery bank.

    • adolph 7 minutes ago

      The cost/invasiveness of cutover is dropping. There is a relatively new category called "plug in solar" where the inverter/battery is smart enought to detect, sync and use grid power.

      The Stream system: Connect the device to the grid to enable it to feed power into the grid or draw power from it when solar energy is insufficient. This can be done via a standard home outlet (if permitted), or through a circuit breaker. [0]

      0. https://manuals.ecoflow.com/us/product/stream-ultra?lang=en_...

    • tonymet an hour ago

      I disagree. During an outage, you need your fridge and a few other essential items. A novice can plug into the back. The device tells you the load and whether you are exceeding. And you can test it at any time. For $600 you can get started without an electrician.

      it's the easiest, safest , most affordable and most reliable emergency solution ever available.

      • brk 38 minutes ago

        For a relatively small battery like that, it's not going to last for days. In the typical outage where that battery would carry you, you can typically just leave the fridge closed and it will stay cold enough to prevent 99% of your stuff from spoiling. For most people (at least the US), it's not super easy to get at the plug in the back of the fridge anyway.

        Running HVAC is usually more of a concern, especially in winter or peak of summer, and those aren't device that you can hot-plug, and a small battery wouldn't help there anyway.

        I like the idea of whole-house batteries, but to really make it practical you're talking about thousands of dollars to the battery, install, etc. And you still don't have extensive run time, which is why I think you see most people still leaning towards permanent or portable generators way more than batteries.

        • jerf 32 minutes ago

          People need to make decisions about how much resiliency they want. A medium-sized battery greatly enhances your options in an outage. A "solar generator" expands them yet farther. A whole-house generator somewhat farther. It's a lot easier and cheaper if you don't insist that your "resiliency" be "I live my life with no compromises whatsoever".

          But I would advocate that "zero resiliency" needs to be seen as being socially irresponsible. It is socially irresponsible that as soon as a service goes out that you are immediately in an emergency. You should not offload basic resiliency on to emergency services. Yes, if you take a direct hit from a tornado you're going to be leaning on emergency services, but the house a quarter mile from touchdown that may be out for three or four days needs to be able to deal with that. If nothing else, emergency supplies are a lot cheaper when it's not an emergency.

          Don't let the perfect be the enemy of the good, and especially so when perfect is so much more expensive and so much less relevant than the good.

          • munificent 20 minutes ago

            > It is socially irresponsible that as soon as a service goes out that you are immediately in an emergency. You should not offload basic resiliency on to emergency services.

            Sure, but that's not a remotely accurate description of a house without a backup battery or generator.

            I grew up in hurricane country and weathered many bad storms. Losing power does not put you immediately in an emergency. If you don't open the fridge much, your perishables will last a couple of days. Non-perishables will last much longer. Having a battery is the difference between "we can hang out and grill dinner for 5 days before we need to hit the road" and "we can hang out and grill dinner for 6 days before we need to hit the road". That distinction does not significantly change your strategy.

            Losing water is a much bigger emergency but is thankfully rarer and a backup battery won't help.

            Climate change will change this story somewhat in the South. If you are in a very hot climate, elderly, or have other health issues, then losing electricity and air conditioning in the summer can be an immediate emergency. Again, though, A/Cs consume so much electricity that a backup battery won't help you much.

            I think you're significantly overestimating the emergency value of a battery backup. Loss of electricity is rarely a rapid emergency. In cases where it is, a generator will at least give you as much power as you care to store fuel.

            • tonymet 4 minutes ago

              Generators don’t work that well. They need regular use and maintenance. Fuel storage is complicated (you will need 30+ gallons a day, or about 2 sedan tank’s worth. Connecting to your panel is expensive at least $2k+. They are smelly and noisy. And if it’s a real emergency, everyone will know you have one , and eventually come knocking.

              For $2k you can buy 3 Ankers and distribute around the house. With a propane camp stove you can cook. So the only utility failing during a power outage is your air conn. If it’s winter you can run a gas fireplace to keep warm.

              In my area we have power outages in the fall and winter wind storms due to trees falling. We need electricity for the fridge, fireplace, lighting , internet & devices. Lithium batteries work great. We get a few outages every season, usually for 2-6 hours .

              My neighbors have a generator for “emergencies” and don’t end up using it because it’s such a PITA. He has it for SHTF, but then he will have to consume the gas from his cars (and siphon it), which means making the decision between home comfort and evac.

              My point is that every solution covers a range of scenarios based on convenience, cost, resilience, versatility and more. There is no one size fits all .

              And now these lithium battery backups provide a broad amount of coverage that is safe and convenient for novices to run.

        • apercu 5 minutes ago

          Fair, but I live in a wooded, semi-rural area and have had 7 outages this year, with one lasting over 8 hours.

        • tonymet 31 minutes ago

          sure we can quibble over convenience, but it's an outage, and you have to make it work. Look at the testing for the Anker Solix S2000 they are getting 2+ days of regular refrigerator use , which is what people care about primarily .

          What other option is easier or more affordable? A generator has to remain outside, so it needs panel connection ($$) , lots of extensions ( $, hassle), needs a generous fuel supply, and regular maintenance.

          And plug-in solar is becoming legal in the usa. within 3 years everyone will be running these little things, and you'll come around.

    • apercu 7 minutes ago

      I mean, yes and no. Switching your whole house over automatically? Yeah, ok, that can get invasive and expensive. Running an extension cord from a battery/inverter or generator a multiport plug then to to your fridge, router and a couple of lights? That's about 5-10 minutes of effort.

      There's a pretty massive middle ground between "plug in a battery" and "rewire the house.

    • fhdkweig an hour ago

      If a fridge is your only concern, they make UPSes specifically for fridges.

      https://duckduckgo.com/?q=Uninterruptible+power+supply+refri...

  • scaredreally 4 minutes ago

    At my mother's workplace, there was a group of coworkers who each donated an amount of money per paycheck. Each paycheck, one coworker would get the lump sum that was collected for that paycheck. Similar concept to the one described here. They called it "susu" or something to that effect. If I remember correctly, it got messy when people would leave the workplace or when, occasionally, someone would get robbed on the way home.

  • balderdash 7 minutes ago

    11-13yr payback on something that is going to degrade ~3-4%/yr for 10 years (and limited terminal value) doesn't seem like the greatest investment unless you think the arb is going to widen a ton.

    • sdthjbvuiiijbb 4 minutes ago

      And any arbitrage is also trivially exploited by the electricity company, who has a much greater financial incentive and scale, so there's really no reason to think that it's going to widen in the future either.

  • kortzeus 3 minutes ago

    The only downside is that the battery won't last 11 years with daily usage

  • jerlam an hour ago

    > 2. Confirm that their home, meter, and electricity contract are compatible.

    This seems like the hardest step. The costs of "just a battery" are much lower by comparison.

    • jandrese 14 minutes ago

      You don't necessarily need to export power, especially for a small battery like tihs. Charge it up when power is cheap, and then configure it to discharge when power is expensive but only to match your current usage. You will need a CT on your main feed for it to balance against, but it can be done.

  • sailfast 8 minutes ago

    The 12 year payoff IF you manage the arbitrage properly really made me wonder why on earth you would buy one of these.

    I want one, yes. But it sure as hell wouldn't be to save money. It'd be to have something if and when the grid falls over due to negligence.

  • thraway3837 19 minutes ago

    You don't really need this, if you have an EV with V2X technology. There's already charging products that work seamlessly: https://www.youtube.com/watch?v=H0WGl_U5azs and you have 100kWh of capacity, so you could sit out an outage for a long time. You can also configure the % cut off for the EV, so you still have enough left to drive if you need to leave.

    EV battery degradation from this use case is irrelevant. EVs are consistently hitting 300,000 miles with 90% capacity, so let's not belabor this point.

  • or_am_i an hour ago

    How does 12 years required for this scheme to pay for itself stack up against the typical house battery's lifetime?

    • Retr0id an hour ago

      Also, as more batteries get added to the grid, the difference between the "cheap" and "expensive" energy prices ought to reduce.

      • rsynnott 27 minutes ago

        Eh, there’s a tension there, becuase on the other hand as more renewable power is added to the grid, you’d expect divergence. Especially in countries which are letting people buy at spot price; that can be horribly expensive, or go _negative_.

    • strbean an hour ago

      Sounds like that's roughly the average usable lifetime for the battery, so you will break even on average.

      • Toutouxc 6 minutes ago

        Roughly the usable lifetime? Based on what?

  • ortusdux 16 minutes ago

    This is what government subsidies/rebates are for - https://news.ycombinator.com/item?id=49298910

    Gift should be ... gifts

  • Tepix 29 minutes ago

    > €1,600 for 5 kWh

    Those prices are high. You can get 2.56kWh for 270€ on Aliexpress, delivered locally from Germany.

  • archydeb 41 minutes ago

    And if you’re in the UK, wire them up to Axle Energy

    (plug-in batteries aren’t actually legal here yet, but likely to become so next year!)

  • well_ackshually an hour ago

    >sixteen people contribute €100 each;

    yeah sure everyone has 100€ to spend on friends, at least once a month.

    What kind of reality does he live in ?

    • Hugsbox 27 minutes ago

      You're getting downvoted, but for real this is so disconnected from what I'd say is feasible for most people. I and most of the people I know live squarely paycheck to paycheck, I can't afford to buy my friends birthday presents at all, let alone set aside that much per month just to put batteries in other peoples' houses. This feels like one of those things where the author doesn't grasp the privilege he lives with.

      • Majestic121 10 minutes ago

        Surely not for _most_ people, but for people on Hacker News, in the correct age range to have a house, putting 100e aside really does not seem out of whack.

        Maybe the author is privileged and it's fine, it's not because you personally can't afford any gift that the author is disconnected, he might not just be talking to everyone on earth.

      • Symbiote 13 minutes ago

        Even where people probably could afford it I think spending €100 on a birthday gift would be excessive. It would be showing off.

      • Tepix 26 minutes ago

        Do they even have houses?

        • ssl-3 6 minutes ago

          Does having a home inherently change disposable income?

        • Hugsbox 19 minutes ago

          In some cases yes, and they're not doing much better than I am.

  • Apreche an hour ago

    Anyone who can afford to own a home can afford their batteries and doesn’t need gifts. Renters are not allowed to modify their home in such a way.

    • Tepix 27 minutes ago

      In Germany you can use a "Balkonkraftwerk" that just plugs into any outlet and contributes up to 800W. You can also hook up solar panels to it up to 2000W (makes most sense with batteries). No need for the landlord to agree.

  • mindslight 35 minutes ago

    Call me old fashioned, but I just bring a can of gasoline and a pile of super soakers.

    While I do like the idea in theory, I don't love the inherent nudge towards off the shelf productized energy storage that will be placed somewhere without much of a plan, and then basically invites rewiring with extension cords. I get how those things are appealing for camping or determined apartment DIYers at the like, but moving them from a seek-them-out "pull" dynamic to a here-you-go "push" dynamic seems like asking for problems from people not thinking too much about storing 5kWh.

  • toomuchtodo an hour ago

    Great piece and post, love the concept!

  • jambalaya8 28 minutes ago

    No.