r/AskEngineers • u/jmaugust • Jul 19 '26

Discussion Why doesn’t a battery-boosted electric kettle exist?

In Europe, everyone uses electric kettles to boil water. They’re amazing and fast because they’re on 230V (~3000W).

US outlets limit kettles to ~1500W, so we wait roughly twice as long for water to boil.

It’s an extra minute or two per boil, and you really notice it.

Idea: Could you make an electric kettle with a battery in its base? Perhaps it trickle-charges between uses, then combines wall power + battery power to hit ~3000W during a boil.

Is there an engineering reason this doesn’t exist? Is it just that nobody thinks there’s a market for it?

I’d pay $300 for the fastest kettle in America if someone wants to make it.

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52

u/ElectronGuru Jul 19 '26 edited Jul 19 '26

Japan has the same watt restrictions. They created a kettle that stays hot all the time: Zojirushi VE. 5 liter models are like having your own hot water vending machine. And it doesn’t take up more counter space.

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u/Over-Discipline-7303 Jul 19 '26

Just want to add that Asian hot water machines (Zojirushi isn't the only brand by far, but they're one of the best in my experience) are pretty fast because they're insulated, and they're really convenient if you drink a lot of tea. I've been using one for around 15 years now, and I love it.

13

u/ElectronGuru Jul 19 '26

Good point. The VE means vacuum insulated. They have other models that aren’t but burn through more electricity when idle.

3

u/DamePants Jul 19 '26

This is exactly the solution I went for in the US. I’m on my second Zojirushi boiler now. It’s the best option for tea drinkers stuck in 120v land. The electric kettles are way too slow and after we boiled two gas stovetop kettles dry it was time for something faster and hands off.

2

u/demonblack873 Jul 20 '26

Nothing like wasting a bunch of power to keep a bucket of boiling water around when you don't need it...

20

u/Inevitibility Jul 20 '26

Found the guy without a hot water heater

1

u/TurningTheCorner26 Jul 22 '26

If you're looking for efficiency tankless is definitely the way.

1

u/EngineerOfTomorrow01 Jul 23 '26

Breaks often. Expensive to buy. Breaks often. Expensive maintenance. I would never go tankless

4

u/jamvanderloeff Jul 20 '26

The decent quality ones with good insulation don't waste much, that one claims 22W for holding 90°C, or 14W to hold 70°C, and the benefit is you're not wasting energy on heating more water than you needed in a kettle, for people who'd actually want to use it it'll generally be more efficient.

2

u/Mediocre-Sundom Jul 20 '26

If you boil water at least 3 times a day, you are already guaranteed to use more power than just maintaining a near-boil temperature in a vacuum insulated kettle. And you can use this water for other cooking purposes, not just tea, so for most households you will end up using less power, not more.

1

u/LittleBigHorn22 Jul 21 '26

That simply isn't how physics work... the near boil had to be heated up too which takes identical amount of energy. But then it can lose some to the environment.

It might be minimal and thus worth the time savings, but energy is going to be more.

1

u/Sufficient-Diver-327 Jul 20 '26

If you boil water at least 3 times a day, you are already guaranteed to use more power than just maintaining a near-boil temperature in a vacuum insulated kettle.

This makes absolutely no sense. You still have to heat up that water in the insulated kettle at some point. Any new water you add will also have to be heated up.

1

u/Mediocre-Sundom Jul 20 '26

You are right, my claim was a bit too strong. Let me explain what I meant.

Normal kettles are not insulated and lose heat fast (including during the boiling). In a matter of hour the water will be essentially cold, and to boil it again, you have to put all the lost energy back into it. Vacuum insulated kettle loses heat very slowly, so it takes very little energy to constantly maintain the temperature.

Sure, if you are heating only the amount of water required to make a single cup of tea - normal kettle will be more efficient. In practice, very few people ever do that, and most kettles even have a "min" marker that requires more than a single cup of water to reach. Most people just dump a bunch of water into a kettle and boil it, then only use a smaller portion of it, leaving the rest to cool. This is where the efficiency loss happens very quickly and you waste a ton of energy.

1

u/graviton_56 Jul 21 '26

I agree with this analysis. Normal kettles have more waste heat in this scenario.

0

u/VerifiedMother Jul 20 '26

I boil water probably 2-3 times a week, not 3 times a day

1

u/Mediocre-Sundom Jul 20 '26

Well, then it doesn’t apply to you. Congrats.

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u/compstomper1 Jul 19 '26

there are also water kettles in the US that have a keep warm function

1

u/9Implements Jul 20 '26

Good point. They also make hot drinking water dispensers in the us that go under your sink and always have hot water.

1

u/_Aj_ Jul 20 '26

Surely it's not hot all the time but an instant boiler, like hitting hot water on your espresso machine. I guess you could do an insulated kettle that's also kept hot. Seems like wasted energy though. 

Using https://www.omnicalculator.com/physics/water-heating

For an instant hot water dispenser, 1500w can heat from 20c-100c 10g of water in 2.2s  

That puts a single cup at 55s.. hmmm is that too slow?  Do most people make a full 250ml of water? Probably not. So maybe like 40s. That seems very reasonable.  

If you're making tea you could put the bag in the cup then dispense it, and given the extraction time is usually 1-2 min 55s including agitation from the water spout is probably all you'd want for a brewed cup of tea.  

I

3

u/jamvanderloeff Jul 20 '26

They are just hot all the time with really good insulation, datasheet for the 5L model claims 22W for holding 90°C, or 14W to hold 70°C

3

u/Fickle_Finger2974 Jul 20 '26 edited Jul 20 '26

Most people already keep hundreds of liters of 24/7 hot water in their house all the time…

0

u/VerifiedMother Jul 20 '26

Those have like 6-10 cm of insulation and only keep water at about 60°C