alt Hacker NewsBuy Your Friends Batteries
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> 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.
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.
There are two issues with the articles calculations, that end up making the already bad payback time even worse, before considering opportunity costs. Numbers are for Germany since that's the more favorable case:
1 - degradation: assuming the 15 years battery life / 10.000 cycles number from the datasheet is accurate, and that the manufacturer considers 70% capacity end-of-life, this pushes the payback time from 11.1 to 12.7 years.
2 - The article calculates the savings with:
> daily saving = 4.5 × expensive price − 5 × cheap price
but this is wrong because it assumes that grid charges fully cancel out. The article generally does a poor job at explaining this, but essentially it proposes you overbuy electricity when it's cheap and use it when it's expensive. The difference of those two, €0.133/kWh - €0.041/kWh is much smaller then the average electricity price of €0.3869/kWh because the latter also includes taxes and grid charges. So with 90% efficiency they end up with the formula above, but completely ignore the fact that from the grid's point of view, the total electricity consumption increased. On the flipside, it's also taking EPEX prices directly, pre-VAT, so you actually save 19% more then the difference 0.133 - 0.041 = 0.092. So the actual formula should be:
> daily saving = 1.19 × (5×0.9 × expensive price − 5 × cheap price) − 5 × (1−0.9) × grid charges
At a average rate of 21 cents/kWh for total grid costs (including VAT) that comes out to a payback time of 13.71 years.
So yeah, buying batteries alone doesn't make sense. You need solar or wind to charge them, so you actually avoid the grid charges. So that instead of saving 10 cents you save 40.
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.
> 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.
People don't tend to buy people large furniture because it's rude to assume that theyll want to keep something large and relatively permanent, much less something that requires an electrician to install.
How does 12 years required for this scheme to pay for itself stack up against the typical house battery's lifetime?
> €1,600 for 5 kWh
Those prices are high. You can get 2.56kWh for 270€ on Aliexpress, delivered locally from Germany.
Strange article, even though the idea is nice. $200 birthday presents might be a thing in America in some circles, but for German standards that is ludicrous (even 50 bucks is quite a lot, and then you need 32 people).
I also don't get his example calculation. He mentions that average price in Germany is 38c/kWh, but in the table it's suddenly 4c min vs 13c max (or 40 vs 133?). That doesn't compute.
>thirty-two people contribute €50 each.
I guess Europeans have more friends than Americans -- I can't think of 32 people I'd invite to a birthday party, and certainly not 32 people that I'd expect to give me a €50 gift. I haven't received a real birthday present from friends (beyond a cheap gag-gift) in decades.
Germany is unfortunately not a good place to do this. The additional fees that you need to pay on top of the actual energy price are simply too high. And currently there is Katharina Reiche in charge which is actively fighting concepts like Energy Sharing.
The hybrid inverter that allows you to plug the battery into your house circuit (DC -> AC) seamlessly is around $2-3k + installation cost, cause you're touching the main panel. Why isn't that in the calculation?
> keep essential devices running when the power goes out
I guess it's very location-specific, but I haven't had a power outage longer than 1 minute in the past 5 years.
It this ad from some battery company?
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.
Do any US states allow plug in batteries like this (I know some allow plug in solar)? The installation cost of a whole home battery is what has kept me away so far.
I don't think installing this kind of system at home is a good idea, especially considering the risk of fire. The amount of energy contained in a 5 kWh lithium battery is terrifing.
A Marstek Venus A 2.12kWh expansion module currently costs 180€ with a bunch of special aliexpress discounts.
The whole system is.. not great, but it's even cheaper to have a battery than this post makes it sound.
This is what government subsidies/rebates are for - https://news.ycombinator.com/item?id=49298910
Gift should be ... gifts
How do I properly think about the fire hazard posed by a big battery in my house?
Welcome to Ukraine where local people installed around 8GWt of batteries at home mostly because of huge outages after missile and ballistic terroristic attacks.
Batteries installation is not about money , average LiFePo4 battery life is around 10 years, so you will save nothing, unless you have some local generation like solar panels. In this case you could shrink payback time to 5 years instead of 10 and it makes some sense.
But the biggest problems here 2: 1. there a critical point after installing a huge amount of balance batteries the diff between day/night hours would be mitigated. And prices may down 30%. As result economical factor of installing energy storage systems would be very questionable. However cheap energy will increase energy usage by homes and industry and this may/might/probaly/i_hope. boost economy
2. The second factor riskier because when many people are installing energy storages and become independent of power grid, or even disconnects from the grid, there still exists power grid you have to support. Right now the price of grid support included in energy bill for electric company. The grid usage price is stable , it doesn't matter you support 1 person or a 1mln residents city. So the less people are using THE GRID - the higher prices for the rest people. And those high price forces rest people to disconnect from the grid. In general we may/I_hope_not to have situation with plenty energy islands and no more national grid systems
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.
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!)
The only downside is that the battery won't last 11 years with daily usage
The example prices of kWH in this article are inconsistent
how often do I have to buy a new one? Batteries are one of the highest cost and most consumable items I can think of.
As the post already mentioned, also great for blackouts, of which more are coming for the developed world given climate change and infrastructure failure
So I could buy a battery for ~$1,850 today that won't even break even in a decade (and hope everything goes well with this plan, not guaranteed in the slightest), or I can buy a 10 year US treasury note that'll give me another $1,000+ in profit at the end of the decade.
Remind me why I should buy the battery? It clearly can't be because it makes financial sense to just have the battery.
This is interesting, but is 3kW enough to be useful? What is the latest when it comes to home batteries? Has management gotten better to be smarter?
>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 ?
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.
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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.
No.
> 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.