[jjcob]

> So you are looking at powering DC only appliances!

Is there anything you actually need AC for? The big advantage of AC is that you can easily transform it for long range transmission. If you don't need that, AC is not really necessary, is it?

I guess the bigger issue is the limited power -- you probably can't use a small scale solar installation for cooking or washing, not because it's DC, but because it just wont offer 1000W power.

[amluto]

Battery powered induction stoves exist, although they are not cheap enough yet. They are, however, truly excellent products. The one from Impulse Labs is not a case of “wow, I can get decent performance without the monster electric hookup it used to require” — it’s “wow, this seems to be the best stove of any sort on the market by a considerable margin, and it’s nifty that it happens to run off an integral battery, too.” If you’re so inclined, you can cook an entire meal or three on it while unplugged.

If someone wants to make them work in rural areas like this, I think the necessary ingredients will be:

1. Cheaper batteries. These are likely coming.

2. More energy. A meal might require 1 kWh or more. (Or less — scrambled eggs won’t require much energy at all.) This is solvable with more panels.

3. Copper. The coil itself is a decent sized hunk of copper. I assume this is part of why cheap little portable induction cooktops still cost $50 or more.

4. Power electronics? I’m not an expert, and I have no idea how much of the cost comes from the power electronics, but integrating the battery and the induction heater seems like it should result in a dramatically simpler system than, say, producing AC from a battery and then converting that AC into a form that will power the coil. The current list price of the Impulse Labs stove includes a hilariously high power output, and a stove targeting rural Africa could be 1/5 as powerful and would still be fantastic.

I wouldn’t be surprised if someone could squeeze the cost of a decent battery powered stove down to $200 in a few years if they had appropriate scale.

[jjcob]

I looked up that Impulse Labs induction hob. Holy Shit, 10kW peak on a single burner is ridiculous!

I already managed to ruin a pan with just 3.7kW (heated it while empty), and I tought that was a lot.

However, I think the cost is probably mostly the battery. Our induction hob (max power per burner 3.7kW / 7.2kW total) costs only 10% of the battery powered stove.

Also, at the low cost, induction is a non-starter. Resistive heating elements are dirt cheap, and the efficiency is not much less than induction. Induction is just way nicer :)

[myrmidon]

Battery power for an oven like this is not necessarily cost-prohibitive; if you want cost effectiveness and long lifetime, LiFePo cells can be had for ~$60/kwh, which would be under <$200 for an ImpulseLabs sized oven.

Absolutely agree on resistive heating for cost effectiveness: Some cheap cells, resistive heating and minimal power electronics would probably be the way to go for the African market.

[hshdhdhehd]

Also https://news.ycombinator.com/item?id=45703666

[gimmeThaBeet]

Dang that 6k is pretty prohibitive not for the overall level, but because it's 4 hobs or nothing. Hardly a "give it a swag" kind of level. I assume they are probably somewhat comparable to the Breville Control Freak, so at a single hob you'd be competing against $1500.

But the battery is a nice philosophy, similar to hybrid/mild electric cars. You don't need all the power forever. You just need more than a 120V circuit can provide.

[jchanimal]

The marginal cost of a hob is likely not the price driver.

[testing22321]

For what it’s worth, cooking a large meal for three (big pot of pasta or rice, brown onions and garlic, brown mince meat, vegetables, simmer sauce) on my induction in my round the world vehicle uses smack on 40Ah of a 12v lithium battery - so about 0.5kwh.

It’s connected with a 3000W inverter.

600W of solar helps a lot.

[jodrellblank]

> so about 0.5kwh

It takes 1.16 Watt-hours to raise a litre of water by a degree. Say 85Wh for 15C room temp to 100C boiling. Assuming your large meal for three is 3 litres, that's 255Wh to get the water boiling. There's energy loss from battery through inverter, through induction. Loss in the pot losing heat to the air. This doesn't count keeping it simmering, or heating the other ingredients.

I don't have any idea if that's very good, to be only twice the theoretical minumum, or quite a room for improvement - have you ever experimented with a 'pot cosy' to insulate the pot and stop radiated heat loss so you can keep it simmering with less power input, or turning the heat off once it's boiling to let pasta or rice cook in the residual heat, or anything?

[ethbr1]

> 'pot cosy' to insulate the pot and stop radiated heat loss

Is this a product that exists?

The closest I could find was ceramic fiber insulation [0], which could presumably be cut to shape and fastened (high temp fastener?) into pot shape.

[0] https://www.amazon.com/s?k=ceramic+fiber+insulation

[jodrellblank]

Yessss, more or less. I learned of the idea from this guy's content[1] who bikepacks ultralight and wants to save camping stove fuel, and he made his own. And from my dad who habitually wraps a thick teatowel around stew pots, on principle (he doesn't measure for a difference in power use. Electric cooktops only, not flame ones). Since it has to be snug on the pot, making one is probably the common way forward.

A few products do exist in that ultralight camping world, the Toaks D95 Pot Pocket[2], the Trangia Pot Cozy[3], Glacier Minimalist "pot with insulating sleeves". In standard size maybe the "So-Vida Sous Vide Insulation Band and Mat for Pots - Protects Your Work Surfaces and Saves You Electricity From Increased Insulation"[5] which is out of stock.

The Wonderbag[6] marketed as for communities in Africa and not available in the USA. From the Wikipedia page on Thermal Cooking[7], in a normal size kitchen people probably go with a vacuum flask cooker, popular in Asia.

[1] https://www.tristanridley.com/post/2019/01/21/diy-pot-cosy-t...

[2] https://www.toaksoutdoor.com/products/coz-m

[3] https://trangia.se/en/shop/pot-cozy/

[4] https://gsioutdoors.com/products/glacier-minimalist

[5] https://www.amazon.com/stores/SO-VIDA/page/BB00BAE8-07C8-4B4...

[6] https://en.wikipedia.org/wiki/Wonderbag

[7] https://en.wikipedia.org/wiki/Thermal_cooking

[testing22321]

No, I never tried.

I have a 200Ah lithium battery, 600W of solar and a dc-dc charger.

To be honest, using up 20% of my battery to cook a large dinner is not a big deal or something I need to improve.

[snickmy]

AC makes power distribution easier (because you can have modulated phases). So it's correct to say it's easier to move it over a long distance. Additionally, and i'm really simplifying, at parity of nominal voltage, you can move a lot more power, at a lower dissipation cost. This has resulted in few high power electronics to be AC native (ie.: no AC - DC - AC conversion). Think about motors in the various appliances, etc. It doesn't need to be like that, investment in DC car motors have pushed the industry to optimizes design, and get similar power output of the motor at lower energy consumption.

That said, if you are a manufacturer of an appliance and you have an addressable user base of billions with AC, and a 'potential new user base' with DC... you might just want to swallow the cost and add a DC / AC converter for the sake to not have to produce two variants of the most complex / costly item (the motor in this case).

[brohee]

That wheel has turned. The king of long distance transmission is now HVDC, to be point of sometimes being used intra-grid and not just for interconnects.

[snickmy]

That is correct. When that will be available is the hard thing to guess.

There are currently enough production of electricity that is motor based (think about gas turbine, water turbines, etc), so there is a nice benefit of having AC at source and distribution.

The infrastructure needs to change. With an average lifetime of a substation in the 50-75years, it's hard to expect we'll overhaul completely the distribution system over night.

It's also hard for me to understand the power loss between the two scenarios (AC production, ac distribution, ac/dc conversion , dc consumption) and DC production, dc stepup to HVDC, dc distribution, DC stepdown and DC consumption). Even 1% at national scale means millions, so the entire business case might be anchored there. I'm sure there are smarter people than me here that can cast some light on this

[SJC_Hacker]

DC is hard to step down. You dont want 10,000 volts going into every house.

AC sill be used for distribution that isnt very long distance

[SJC_Hacker]

Long distance yes. But medium distance AC is stíl cheaper.

You also need to step down that voltage to 240/220 for residential use, much easier to do with AC

[mschuster91]

> I guess the bigger issue is the limited power -- you probably can't use a small scale solar installation for cooking or washing, not because it's DC, but because it just wont offer 1000W power.

Your average lead-acid starter battery can easily do that - 1 kW is less than 100 amps at 12V, less than 50A if you wire two in series. 200 Ah means about four hours worth of runtime.

The problem is switching off higher DC voltages and currents. AC is easy, it traverses through 0V 100 (or 120 in the US) times a second. But DC? The arc is just going on. That's why most electrical equipment, from switches over automated breakers to fuses, has distinct ratings for AC and DC, with DC ratings sometimes being half the AC rating.

Additionally, larger DC networks tend to have issues with weird current flows and electrochemical corrosion.

[nativeit]

Could it easily do that for several minutes at full chap? Under the load of a full washing machine?

[kragen]

No, only for about a minute or two. But there are a lot of lithium-ion batteries capable of 10C discharge rates which can survive several minutes of max load. For 100 amps I am guessing you'd need 10 amp-hours of 10C-capable lithium-ion batteries, roughly a 4S4P or 4P4S configuration of 10C 18650s. I think this is about US$128 of batteries, a similar price to the car battery but much smaller and more inflammable.

[rozab]

Lowtech magazine recently had an article about cooking with solar power:

https://solar.lowtechmagazine.com/2025/10/how-to-build-a-sol...

[Driver8]

They also did one on using DC directly instead of AC and the benefits of doing it: https://solar.lowtechmagazine.com/2016/04/slow-electricity-t...

[kaon_2]

Thought provoking question! I am not an electrical engineer, but arguments I heard went along these lines: Almost all existing appliance markets are AC. Are we really going to be building a complete parallel appliance market? You wouldn't be able to sell a TV from the city in the country side and vice versa. I would be keen to hear what an electrical engineer on hackernews has to say!

Interestingly, when I visited the countryside, I saw some AC electrical appliances. One elder couple had an enormous 80ies style stereo-set gathering dust in the shed. I was told they were a wedding gift.

[looofooo0]

Laptops, TVs and other electronics already run from DC. Also, there are a lot of appliances for camper vans, boat which run on 12v or 24v DC. On Alibaba you can buy a stove for a few bucks: https://www.alibaba.com/product-detail/Solar-DC-12V-24V-Batt...

[Gibbon1]

I'm sort of an electrical engineer. Increasingly things don't run directly off 120/240V directly. Anything with a power supply could be designed to run of 48V DC nominal. My slight obsession is that really the world needs a low voltage standard. Things like lighting, low power appliances don't need 120/240V.

[snickmy]

I'm with you, and actually bullish on this to be a viable way forward.

48V DC has been eyed already for a potential standard to emerge. Doesn't need massive cables to deliver decent power (4A ~200W). There is enough hardware around coming from use cases like EV and Boats that could make it work. Many battery solutions already 'talk' 48v without lossy stepdown of voltage, etc.

Big plus is that the regulation is A LOT less strict for <48v DC compared to AC 110/220/240.

[lesostep]

I worked as an electrical civil engineer for few years.

>> the world needs a low voltage standard we have high voltage standard because it means we can have low amperage to transit same VA.

Because voltage doesn't kill, amperage does. It's for safety.

DC is far more safer then AC, but it's not that much safer. If we convert 20A 240V AC (very bad, you can't move your hands away) to 48V DC we get a wooping 110A (instant death)

But if we convert 20A 120V AC, we'd get 55A 48V DC. It's on the same level and has the same problem with moving your hands away.

My country used 220V (as most do!) so switching to DC would mean huge safety threat, but for 120V countries I'd say – go for it!

[TheTxT]

Not an electrical engineer, but doesn’t the voltage combined with the bodies resistance dictate the amperage? So anything under 50VDC just can’t transmit enough amps through the body to be harmful?

[nativeit]

This is correct.

[KeplerBoy]

I'm slightly afraid of a world where USB-C PD is going to be that standard.

[Gibbon1]

Perish the thought.

You plugged your class EVTF television into a class ETVF receptacle and your TV caught fire? Shame shame on you.

[kragen]

Thermal energy storage solves the problem of cooking and washing.

I have a half-liter thermos bottle that leaks about 0.3 watts at ΔT ≈ 50° (635g of water dropped from 71.9° to 69.8° over five hours and 8 minutes), so any power supply averaging over about a watt would be sufficient to boil water in it—eventually. If you needed to do it in the 4 hours the sun was near peak on a single day, you'd need at least 15 watts. (I don't live in Africa, but I do live in a third-world country. Blown-glass thermoses are pretty widely available because, although they're fragile, they're light and never wear out, just shatter.)

Sand batteries are potentially extremely cheap and can easily deliver cooking temperatures. A super-low-tech version of this approach is "salt frying", where you preheat a few kg of table salt (melting point 800.7°) to frying temperature, then stir dry food into it. Most of the salt won't stick to the food, but the few grains that do won't cause the edibility problems that sand would.

TCES potentially offers much greater storage density and much greater controllability than these sensible-heat energy-storage technologies, since you can store the "heat" indefinitely.

Phase-change thermal energy storage is another potentially appealing possibility, potentially offering a stable cooking temperature for many hours, although I don't know of any suitable materials. The MgCl₂-KCl–NaCl eutectic, for example, doesn't melt until 401°. Maybe something like calcium stearate (m.p. 150°–180°) would work, but its heat of fusion isn't great, I'd be worried about long-term stability, and although it's easy to get anywhere in the world, it's probably a lot more expensive than salt. (Table salt is US$100/tonne, but the eutectic mentioned above would be closer to US$400/tonne.)

[potato3732842]

Ignoring the cost of the battery how much does a cordless drill that'll break your wrist cost? A non-trivial amount more than the corded one that's for sure. You're gonna see comparable cost difference in just about every "final appliance" that actually turns the jiggling electrons into results (whether those results are work or heat).

Alternating current is substantially easier to step up/down in voltage, much nicer to anything that modulated current flow and has a lot of convenient aspects for motors. Like for like the DC solution costs just a little bit more every step of the way.

Even if you're not doing long distance transmission the cost of all those things that are worse about DC are going to be bore across the entirety of your economy that uses AC. DC makes sense here because the supply chain is so dysfunctional that making the "better" solution work would actually cost more than the "12v doodads from china" style solution. Eventually as electrification continues the choice of DC will become a drag though.

[kragen]

I don't think this is correct. Drills use "universal" motors which don't care if they're running on AC or DC, because 60Hz AC motors are limited to 3600rpm, which isn't nearly fast enough for a drill, and also because it's not okay if the drill stops working if it hits resistance and slows down. (Most AC motors run at a fraction of that.) You can run a cheap electric drill off 120Vdc just as easily as 120Vac. Getting it to run on 48Vdc or 30Vdc involves rewinding the motor with the same amount of copper in the form of thicker wire.

Fancy drills already have a lot of electronics that do care about the polarity of the applied voltage, but they usually want it to be DC. Once you get anything more sophisticated than phase-angle control with a TRIAC, you're using MOSFETs anyway, and you can often use half as many of them if you're using DC, because MOSFETs like DC.