Your math is correct as are you assumptions- it is not on all the time, but it will still be expensive to operate.

Like a hot water heater, an instant hot does not run all the time. It is in essence a mini-hot water heater. It will heat up 2/3 gallon water to 200 F, then shut down. When the water cools enough, the thermostat will turn the heating element on again. It will still be expensive to operate, because the greater the difference between the contents and room air, the less efficient the insulation will be.

I use a single burner induction hob to make boiling water. Very efficient. In fact, I sold my tea kettle because the induction is so efficient and fast.

goldie,

If you really want one of these, one way to save energy is to install one of those 24 hour timers on the thing. Say you want a cup of tea at 7:00 AM in the Morning, but will not use it until people get home from work at 5:00 PM.

Get one of those plug-in timers from a hardware store. Set it to come on at 6:00 AM, then shut- off at 8:00 AM, then back on from 5:00 PM until 11:00 PM.

Regular hot water heater timers work on the same principle and can save 20% or so on the electric bill. You obviously won't save as much, but I bet the timer would pay for itself in a couple of months.

Of course, the microwave is already there so ...

More information. I called InSinkErator and talked with Jenny. She said that the units use the energy equivalent to a 40-watt light bulb. So 40-watts at 27/7/365 is about $36 per year to run. I am not sure I believe that since those caculations are based on how much usage---one cup per day or ten cups per day? The microwave as a point-of-use would be cheaper to run than maintaing the unit, though. Any additional thoughts?

I would believe what they say. The only thing to look at is how much it costs to maintain the heat. Creating heat for actual usage, is similar to if you use an electric cooktop or possibly better due to the fact that the element is in the water itself.

Put another way, you want to know how much worse this is compared to heating water the conventional way. So it all simplifies to heat loss while the unit is doing nothing.

We have a Franke unit. I just measured it when it was sitting idle and it was using no power. I used some water and it kicked back on to 720 watts. I don't want to leave my meter running to measure the average because we hardly use ours! The main use ours gets is for washing things in the sink (when needed).

We have a dedicated hot water pot we use with teflon inside, etc. We use it for making tea and such where even the slightest off taste makes the tea unpleasant to drink. And our Franke has always had some of that. Mabye others have better luck with them in this regard. In addition, the stand-alone unit is able to keep percise temps you dial in for different kinds of tea, something that is hard to do with under-sink units.

The Zuji stand-alone unit has an electric pump (read, easy to use) and is super insulated. Its outside is colder than that of Franke by far. So I think it is more efficient that way. The one we have holds more water than the Franke to boot so when you are making a pot of tea, the next person doesn't have to wait.

goldie: There was an older model of istanta hot in our kitchen when we moved in. When I disconnected the unit, I noticed a change in our electrical consumption month-over-month.

WOW, I'm sure glad I read this thread. I hadn't really thought much about a hot tap in my kitchen reno, but several friends have gushed about how convenient they are, and how they are "must haves". I think my best/efficient method of boiling water will remain my electric kettle. Not only does it use less energy, it really boils!

I have a device called kill-a-watt that you plug an appliance into then plug into wall. It tells you exactly how much it is costing to run the appliance (kilowatt hours, amperage, voltage and more). Our stand alone hot/cold water dispenser was $30 more a month with the instant hot on than with it off. Being that the induction cooktop boils water faster than a microwave can heat it, the cooler is off.

Klaa2----holy hat! That information is so interesting! I am thinking of this new process of building our house like this: just because you can do something, it doesn' mean that you should. If I'm using compact flourescent lights as much as possible around the house, solar energy, etc... it seems counter productive on a small scale for me to have the instant hot faucet. Sure it is just one decision, but it has me thinking....

I think some context here is important. Any device heating up water is going to use power. That power needs to be subtracted from the energy usage of this device to figure out its true operation cost. That is, the only cost is maintaing the water temp in the little tank.

I believe the company when they say that is equiv to 40 watt light bulb. When I put my hand on the unit, it is only slightly warm so it is pretty well insulated. 40 Watts translated into monthly cost adds up to $2.30 in our area (electricty = 8 cents a KW). If the bill is $30 it is because of usage and/or poor insulation of the heated water.

Mind you, I am not trying to recommend anyone get one of these. There are many reasons to avoid them starting with short life and water taste I mentioned before. But power usage is not really a factor. I am sure I go through a ton of tea bags costing far more than $2/month :).

Short life of the unit? I hadn't heard that before. Please go on.... Tell me more.

Depending on type of water you have, the machine's life becomes as short as 4 years. I think hard water is well, "hard" on it :). I did a quick search here and the very first hit shows this: http://ths.gardenweb.com/forums/load/appl/msg01021911334.html

"I have installed 3 of these units (two of the most expensive Insinkerators and one other brand that I can't remember) over the years. Every one of them has broken within 2 years of the installation, so I would stick with the microwave heating option unless you like non-functional instant hot water units sticking through your granite countertops.

My installations were all in the SoCal area, where the water has a lot of minerals in it, so the dispenser's longevity MIGHT improve if you live in a soft water area. I would spend my money on something else, though."

Everytime I read a thread, there are comments like above, including people who have taken them apart and found less than pleasant inside.

Of course, keep in mind that all of this is second hand info. Ours is still working although it doesn't hardly get any use and our water is not hard.

Here is a link that might be useful: instant hot issues

Lowe's has a version made by insinkerator for $173.00. We did not notice a spike in our electric bill when we installed ours. We LOVE it, but then again we live in the north and drink hot drinks all day long in the cool weather and use it to brew tea for iced tea in the summer.

This is a little OT, but I want to share my tale of a recirculating water device. I bought one at HD for $200 to get hot water at my kitchen sink faster, which according to the box would save energy, save water, cure male pattern baldness, and all sorts of nifty stuff. Plumber installed it at the upstairs bathroom sink (which was further away from the hot water tank). Water coming out of that faucet was never cool -- lukewarm at best. Plumber explained that it was a design issue. More importantly, my gas bill tripled. Maybe I saved a gallon a minute, but I sure didn't save energy. It turns out that hot water circulating is water always being reheated, unless your builder was so prescient as to insulate all hot water pipes. I'll stick to microwaving my water for tea, and do something intelligent with the extra gallon of water needed before water starts running hot.

blue - Thank you SO much for confirming something that I have long suspected. That recirc never made sense to me - If your pipes are not well insulated then you are losing a lot of heat all the time as opposed to just when the pipes are freshly hot. If you are approaching a perfect world where your pipes are so well insulated that they do not lose much heat, then you do not need a recirc anyway.

Within the last week or so I did a google search to see others' opinions on this. The only places that I could find that said it saved energy were sites selling these pumps. Go figure.

Maybe there is some place in the world where a gallon of water is more precious than the energy needed to warm it, but unless you live there...

recirc pump does have that issue. I have seen an install on TV which used a motion sensor to turn it on though. If you have a security system and smart wiring, you could use that motion sensor just the same.

In our case, if I turn off the recirc pump, you just can't use the kitchen faucet. You could wait minutes and it never really gets hot. With the pump running, you have hot water nearly instantly. So it is a case of necessity, rather than convenience.

In our vacation house prior to remodel, we had two hot water heaters, one for each side of the house. That worked better than the recirc. So even though our GC doesn't like it, we are pushing him to go that way rather than use the pump. So if you have the space, do look into using dual water heaters. You also get more hot water capacity this way and showers, etc., at the other end of the house doesn't impact the other system.

As an aside, I would never drink the hot water out of the pipe or for cooking. You don't know what is sitting in your hot water tank :).

Insinkerator published an energy analysis for their dispensers Insinkerator Energy Use which supports the claim that use is equivalent to a 40W light bulb. So in my area, with electricity at $.13/KWH, the annual cost will be about $45.

This is the best write up I could find. May save water, not really save energy

https://www.saleappliancesltd.co.uk/blog/built-in-appliances/does-an-instant-boiling-tap-use-more-energy-than-a-kettle