Reservoir: Smart electric water heater
Mood
supportive
Sentiment
positive
Category
tech
Key topics
smart home
sustainability
IoT
energy efficiency
Reservoir is a smart electric water heater that aims to optimize energy usage and reduce waste. The product is showcased on its website, sparking interest and discussion among HN users.
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- 01Story posted
11/15/2025, 3:50:04 AM
4d ago
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11/15/2025, 7:31:15 AM
4h after posting
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11/15/2025, 5:13:18 PM
3d ago
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For people wondering what's up with the "150 gal virtual" capacity, it's actually a 47 gal water heater but it heats water to a really high temperature (if needed) and mixes it with a thermostatic valve to output the desired temperature. For example if cold water was 15 degrees C and you want the hot water to be 40 degrees C, it can triple its "capacity" by heating it up to 90 degrees C and then mixing one part hot water with 2 parts cold water to give you three times as much hot water. Of course, this comes with a grave penalty to efficiency so you should only do it for "party mode".
The thermostatic valve makes it so that the water that comes out of the water heater is at a more reasonable temperature.
If the automatic mixing feature malfunctions to super-hot, then it could be risky...
[1] https://www.verbraucherzentrale.sh/pressemeldungen/lebensmit...
Yeah, they put the word 'virtual' in front.
Still, really annoying when half way through your bath, the fuse would pop, colder water now coming out, and you'd have to completely dry yourself to reset it and wait for whatever got too hot to cool down enough to get the other half of the bath going again.
it's a tankless natural gas heater in our case, heats endlessly so there's no sense of virtual tank capacity.
This project seems emblematic of the challenges facing funding manufacturing initiatives in America. What's funded are the projects that appeal to tech investors, more of a focus on flashy presentation, luxury design, AI, and cloud app features, than the baseline functionality.
We get innovation as a side effect of convincing investors that the idea will disrupt industries and create app ecosystems that lock in consumer attention. Chasing the 100x unicorns and no longer training workhorses
These things sound so obvious when you don't factor in the annoying little details like transmission of energy. System complexity also matters. There's this thing called "total cost of ownership" that paints a more honest picture regarding how these economics interact.
Using heat pumps to solve a problem looks fantastic in operational efficiency terms, but what happens if the control board breaks and the vendor decided to move on? Dumb, slightly less efficient appliances might actually be cheaper and better for the environment in total. If I have to create a pile of e-waste every 3 years just to save 10% on my energy bill for something that is already incredibly cheap in absolute terms, I think it could be argued I've made everything worse.
They quote $2,500 10-year savings vs oil. I have my hot water piggybacked on the oil-fired condensing boiler unit that's also used for my central heating, and I doubt I burn more than $250/year total on the hot water side of the equation (in a 4-bed, 4-bath house).
That places my central heating on the order of 5-10x higher energy expenditure than my domestic hot water - this does not seem atypical in my area, and apparently data for the entire EU is similar (60% heating, 15% hot water): https://ec.europa.eu/eurostat/web/products-eurostat-news/w/d...
With the heavy use of direct combustion for home heating in the US, heating wouldn't be hugely interesting in that context. I consume more natural gas for heating each month in the winter than I do for hot water annually.
"Space heating" is also on the same graph, and it's nearly 1-to-1 with water heating. Which seems odd
The last "intelligent" systems that made sense to me in the home are variable speed HVAC and micro grid / solar / battery stuff.
What is the value add to the customer of making hot water an app that can presumably stop working the next time AWS goes down?
However, the website has some weird vibes as well, like why would you say something like below?
> And some just want Dad Mode for when your teenager needs to finish that shower.
But the end result makes me cringe after all.
Edit: oh, you're talking about this product website...
One thing I learned from the video was how do water heaters get away with giving higher capacity numbers than they actually have. Well, apparently, kind of like air, hot water also rises and the heater keeps working while in use and it also has secondary heater element it can switch to, so it can follow the cold-hot water separation line.
Never worry about running out of hot water ever again. If I’m gone on a trip for 2 weeks my hot water bill is zero. Due to having overcapacity, whenever I have guests staying with me no one ever has to worry about simultaneously using showers or any other hot water at all. I run out of water pressure before I do heating capacity.
If one breaks I just schedule a repair or replacement for weeks in advance and have to limit folks to 2 simultaneous showers at any given time. Hasn’t happened yet.
I will never go back to a tank based water heater unless outright forced into it. It’s one of those “TiVo like” upgrades to your lifestyle you never knew you needed until you have it.
Certainly not cheap, but also not prohibitively expensive if you can find a competent installer who doesn’t overcharge.
1. Can’t have recirculation pump to supply hot water instantly throughout the whole house.
2. Significantly higher energy bill compared to heat pump.
An additional bonus is the heat pump cools my garage in the summer.
And hopefully the smart part is not relying on external connections or services. Otherwise next time the cloud service goes down you end up taking cold showers, both figuratively and literally.
Pay EXTRA for a water heater that collects data on when you shower, how much water you use, and at what temperature, so that they can sell that that to someone who wants to serve you a towel ad on your smart fridge screen after you get dressed.
Which says you are putting up a high upfront cost, hoping to recoup on increased efficiency. Which could be worthwhile, but you would have to run some simulations if the price is worthwhile. Seems potentially easier to get a dumb water heater to run extra hot using off-peak electricity.
Long term support for these internet connected data miners is my first thought.
Gimmick is my second thought.
Pay EXTRA for an over engineered water heater whose company sells your data about how much water you use, when you use it, and at what temperature, so that costco or someone can serve you a towel ad on your smart fridge screen after you get dressed or do the dishes.
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