Mini-review: Bosch Ariston 4-Gallon Point-of-use Water Heater


Does it take a long time for hot water to get to your sink? Do you think that it’s wasteful to run the water for a minute or two just to be able to wash your hands? Have you thought about installing a recirculation system for instant hot water? If so, this unit might be for you.

I had all these issues in my kitchen because the kitchen water run is quite a distance from my main water heater. So we just got used to washing our hands in cold water. And if we had to rinse some dishes and some needed hot water, we would turn the hot water on full and wait…and wait…and wait until some hot water came out the faucet. I knew there had to be a better way.

For years I’d researched water recirculation units and found one, the Chillipepper, which people seemed to really like. However, I have granite counters and no convenient place to drill a hole for the power switch. I also have other fixtures on the kitchen water line and I didn’t want my wife to have to remember to push a button and wait for hot water. Finally, because I have long pipe runs from my water heater, this still wouldn’t solve the problem of wasted energy because gallons of hot water would be left in the pipes.

After doing some calculations and determining that any solution using the main water heater would waste several times as much hot water as a point-of-use unit, I broke down and bought one of these mini-water heaters.

Our house has a utility closet in the basement that is directly under the kitchen, so I mounted the unit in there. Plumbing was easy for me, but I’ve done a lot of plumbing work. Most people would need to hire a plumber to install the unit. But because of its size, installation is a snap.

Some people will plumb the cold water intake to the heater from the hot water feed to this part of the house. There’s some logic in this, in that if you need lots of hot water, this heater can provide quick water for hand washing but if you need more water, it flows into the tank and provides you with a much greater supply than this little heater can provide. However this still leads to a lot of wasted energy because you’re leaving all that hot water in the long pipes every time you use a little water to wash your hands.

Instead, I chose to connect it to the cold water supply. My logic was that the kitchen sink really should not be used for long washing sessions. rinse a stubborn dish or wash your hands and that’s it. I also had an ulterior motive – if there was only a few gallons of hot water available, it would force my family to use less hot water. Additionally, our washing machine is on this water circuit, and I prefer washing in cold water but my mother-in-law, who likes to come over and do our laundry (don’t ask!) is old-school, and insists on setting the washer to ‘hot.’ Now she gets the satisfaction of thinking she’s washing in hot, but I know the water heater can only supply a few gallons of hot, so it ends up providing the first few gallons of hot water for the primary rinse, but after that, it can’t keep up with the demand. I consider this a bonus energy saving!

The unit uses normal 110v house current, so you just plug it in a nearby outlet. However, I would recommend a dedicated circuit or one that doesn’t have other heavy loads on it because electric water heaters pull a lot of juice. If the water heater turns on at the same time as you’re toasting some bread, you’ll blow a circuit breaker. So make sure you plug it in an outlet on a circuit that is lightly used.

As far as heaters go, this is an attractive unit. As you can see in the picture, it has a white plastic case. Nothing special, but not just an ugly metal box like most. But really, it goes in a utility closet, so they could have painted it any color they wanted and I wouldn’t have cared!

Does it Work?

The main question is: does it work? The answer is “yes,” up to a point. We can now wash our hands and run the dishwasher (which has it’s own super-water heater built-in). As noted above, it also provides hot water for our front-loader washing machine, but because of its limited capacity (four gallons in this case) it won’t provide a lot of hot water. You can wash for a minute or two before the water runs luke-warm then cold. This can be a plus or a minus depending on your needs. I know some people would find this objectionable. But that’s just the way these things work. They enforce water conservation and force you to change the way you use hot water. If you don’t like this, then a small point-of-use water heater is not for you!

Energy Savings

Like all good geeks, I measured the actual electricity use of the water heater. Because it just plugs in an electrical outlet, I plugged it into my kill-a-watt meter, and make daily measurements to see how much energy it is actually using. I’ve been very pleased with the results so far.

Under normal usage – rinsing a few dishes and regular hand washing in the kitchen sink, it consumes 1.5 to 2.0 kWh of electricity per day. This is about 1/3 the electricity that would be required if I used the main electric water heater and just “lost” the heat in the pipes every time I used the sink. On laundry days, this consumption increase by about 2-3 kWh (about 20 gallons of hot water). So we’d still be better off always washing in cold water, but some habits die hard….

Conservatively, I project that for my family, with it’s modest hot water needs, this unit is saving me about 4 kWh per day (about 25 gallons of hot water). That may not sound like much, but over the course of a year, that’s 9,000 gallons of hot water and about 1,400 kWh of electricity. For most people, that’s a full month of electricity saved every year. In my area, that’s a saving of $232! I’ve checked on Amazon.com, and this water heater cost $169 when I wrote this article, so it pretty much pays for itself in the first year if you install it yourself. If you hire a plumber, it may take a couple years to pay off. And, I haven’t included the ecological and financial cost of the water you’re saving.

Addendum – this is not an “on-demand” water heater

To avoid confusion, I should add that this is not an on-demand water heater. On-demand water heaters use much more powerful heating elements to heat water on-the-fly. They provide an infinite supply of hot water because they heat water as needed. The Ariston water heater is just a miniature storage tank water heater. So it’s the same as a conventional water heater, but tiny.

Support my continued work. Buy it here on Amazon.com

Note on my Amazon store

Like any informed consumer, it probably raises red flags when you see someone reviewing an item then potentially profiting from it. I couldn’t agree with you more. For years, I refused to profit from any of the products I’d recommend to my clients for fear of conflict of interest. But then my wife convinced me otherwise. She said “you’re recommending these products because you buy them and believe in them, not because somebody is paying you to do it. How does it compromise your principles by gathering the products you recommend into one convenient place?” How could I argue with that logic?

So now, whenever I find a cool product, most of which I’ve purchased for my own use, I look it up on Amazon. I check the reviews and make sure that the actual seller seems legit and then add it to my “store.”  I don’t really have a real store. It’s just a convenient way of pulling together the products I’ve found and like.

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3 thoughts on “Mini-review: Bosch Ariston 4-Gallon Point-of-use Water Heater

  1. Solar water heaters. These types of water heaters rely on the power of the sun to heat your water. How efficient they are depends on the amount of sunlight they get so this usually depends on where you live. The more sunlight the better and the more intense the sunlight the better and if the climate is hot in the first place then the water is sort of pre heated to ambient temperature before the action of the sun. They are a good source of some hot water but are not really good enough to be classed as your main water heater so you will need a conventional water heater as a backup. Solar water heaters can also be used to help warm the water in your pool and for this they can be very efficient but again they rely on sunlight to provide a high enough water temperature. I have one of these and I am very impressed about how good it is as a water heater for my pool. It wasn’t cheap though.:

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  2. Any idea how it fares on standby? Have you ever left the kill-a-watt on it over a vacation weekend, for example, to get to something like “idle kWh/day” ?

    • I’ve kept a kill-a-watt on it continuously since installation and take measurements every morning. Standby losses appear to account for about 0.5 kWh/day. Connected the way we do to furnish hot-water for the kitchen sinks/dishwasher/laundry, our typical use is 2-3 kWh/day on top of that.
      I installed it “as-supplied”. It has built-in heat traps, but they’re not very effective, so you can tell it’s wasting energy that way. I may try re-plumbing it to better trap convective losses which I think will help.

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