Is there is cost saving for you in having a tankless water heater?

I would like to know if you have experienced cost saving by switching to tankless?

If you have a whole house or just one faucet?

What brand do you use and do you like it?



Tags: garden, heaters, hot, plumbing, tankless, water

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I haven't personally switched to tankless but have been involved with hundreds and have feedback from dozens.  Most all of them are one unit supplying the entire house.  Some have a second unit and others have tankless for the master and tank for the rest of the house.  

They seem to work best if it is centrally located.  Singles and couples seem to have better cost savings.  Families with teenagers or overgrown kids that like long, endless showers drive the cost savings out of the house! A poor location with long runs will decimate savings. It is not a one fits all scenario.

I have a gas fired tankless hot water heater installed in my basement  for the past 8 years.  Air supply and exhaust is a double wall direct vent system.  Great system as you can run more than one shower and washing machine and dishwasher at the same time and still not run out of hot water. .In the summer when we do not run the gas fired hot air furnace our gas bills are in a range of $13.50 to $20.00 which includes a monthly meter charge of $8.55 per month. The higher bills are the past several years since we installed a gas clothes dryer and we do a lot of laundry.  You do need to service the unit periodically (flush the water lines with an acidic vinegar solution to remove lime scale build up in the heating coils). New homes with piping runs designed for a tankless avoid running a lot of cold water down the drain waiting on hot water.

Its just so confusing! I dont know what brand or model to buy? I found so many websites but still not sure. I need help, this is one of the websites

Can someone tell me which one I should buy for the whole house 6 people. 2 adults and 4 kids all over 12 years old.

Any help would be much appreciated.


I have a Rinnai unit, rated at 199k input.  Other brands work fine.  Size by selecting units that will make at least 5 or 6 gallon flow rate at 125 degrees outlet based on the local inlet water temps. Select yours from a dealer that has installed lots of tankless units and talk to some clients from several years ago..  If he cannot give references, try another company.  These units cost more than tank type units, unless you are looking at heat pump type water heaters (another choice if you do not have natural gas and in some local areas there are rebates available to help pay for the cost difference of a heat pump type versus a standard electric tank type).  Be aware you will need a larger gas line than if you were using a standard tank type gas water heater.  This adds to install cost.  I have a 3/4" gas line to the Rinnai and only a 1/2" line to the Lennox hot air furnace.

The only actual experience I have with electric point of use hot water heaters is in the UK where they often have a unit installed into the water pipe right above the shower head.  With the visible wires  to the unit, I always wonder about running electricity and water together just before the water hits my body.  So far, so good......

It isn't only the number of adults and the kids in the house.  Your usage patterns are also important.  Put a note pad by each sink, shower/tub and have family members keep track of when and for how long they've used HOT water.  Then you can go back and estimate the flow rate of the water used.  Flow rate determines the size of the tankless.  The hot water system pipe design, long trunks or end runs, size 1/2 or 3/4 for trunks,  will then give you an idea if you'd be seen a little water sandwich (cold plug of water), or a big sandwich.  

You need to look at the fixtures,  are they low flow fixtures, or higher flow... low flow fixtures may not trigger some of the less expensive tankless heaters to turn on.

Look at when you do laundry and use the dishwasher,  keep track of the time.  Record it in the note book.

Check your water for hardness and minerals.  

Then once you've got all this down,  estimate for how long the water would be running (hot water), and the flow rates (you can measure flow rates by capturing one minutes worth of shower water in a bucket and measuring the volume).

Calculate what you think you need for sizes, put it on a piece of paper that you can hand out to plumbing contractors that you'd buy and install the tankless unit.  Let them ask questions and estimate ;sizing... then ask them to explain.

If you do the work up front,  it will be far easier to choose the unit AND you will be happier with your choice of units.

Right size for a tankless water heater basically depends on how many gallons water will be coming out of the taps at the peak hour i.e. when everyone likes to shower in the day. Simply add 2 gallons for each faucet and shower head that will be in use to find out your maximum hot water usage. You then estimate how many BTUs are needed to heat so many gallons and that needs you to know the tap water temperatures in your city. Naturally, you are going to need more power if the water that enters the water heater is very cold. Here is an article on tankless water heaters. Sizing and some other features are explained under the title: What Features to Look for in a Good Tankless Water Heater. To get good results, I suggest you do some research first and then seek professional advice and installation.

Thanks Theodore, perfect info.

I do not have a tankless unit installed but I wish I had. According to the my tankless water heater expert, there are not much difference in savings between a tankless unit and a very efficient tank unit.
However the real savings are in preventive maintenance and space savings in a home. If your tank unit breaks inside the home and no one is home, then you have a costly repair and replacement job. Also space in a home is normally valued at over $140 per square foot. A tank unit occupies over $1,000 of valuable interior space that could be used by me or my wife for extra storage space. The tankless unit is normally mounted on an outside wall and does not occupy or put at risk valuable interior space.

Since solar hot-water units are cheap vs anything interior to a home and the water tank can be near the collector, I'd argue your using coal for at least 1/2 your power not sun and that's obviously ruining the planet when on the grid.

Solar works well if you have a reasonable solar insolation.  Pretty difficult to use solar during the winter time in Alaska.  Electric hot water heaters in Washington/Oregon most likely get their electricity from hydro.. not coal.

Solar hot water heating in the NW is more expensive than NG or electric.  

A heat pump hot water heater also uses less electricity than a generic resistance heater.

Location is important... the type of heater is important...selecting the hot water heater that matches the available resources is important.

It isn't good idea to presume everyone's power comes from coal.

The grid mixes power, you can't tell where it came from unless you're doing the mix, it's a big money game so very complex with demand & supply with preference to fossil over wind and hydro, they don't mix it to cost the least to the consumer, pipe dream. Mini-grids are popping up due to this and alternatives the choice with large-scale battery arrays in containers at 1.5Mwh each it's the future, grid and miles of wires is dead.

For the Arctic a system I'm working on for home-ranch-farm is biodiesel made from your own septic tank effluent, to do this uses photo-bioreactors, climate control, aeration, light piped in, they stack to reduce footprint being 14" cubes plus insulation on sides with a base and top to complete connections.

Beyond hot-water, this produces enough for home heating, a truck & snowmobiles if a family with dogs, the Inuit or anyone burning diesel all winter will jump on this instead of paying by the barrel. Most biodiesel produced in the USA is used for heating, about 1/3 of producers use wastewater as the feedstock.

Heat pumps are right on in general, good investments but still need power from some source, of course each home & site should dictate choices along with the budget.

I've never heard of solar hot-water being more expensive than fossil fuels, it's a shallow collector nowadays mostly DIY. There are 80's collectors in Seattle they put in the attic, nobody does that today.

Collector hot-water as the source use heat-exchangers as "burners" that are available from several brands of tank and 150-gal common as adequate mass to maintain itself, withdrawals a smaller percent. Most off-grid use an on-demand in the system for backup so that would be a larger capacity for high latitudes.

Something on the horizon is long infrared which can be collected at night, researching that. A strong suggestion to anyone in cold climates is insulate the outside of your walls, put up furring strips and siding over that to hold the cold wind off the wall.

I got onto this with tiny sheds, the ones with insulation board on the outside stayed warm way better, recently did heat-transfer modeling and it's 3-4 times more thermal resistance than the same R-factor as batting between studs, ymmv.

Not entirely.   ERCOT (Texas) is essentially its own grid.

The grid is broken into regions,  with system operators (ISO). They can track and tell you the source of generation.  AC from west coast is not shipped to Florida - instead it is pretty much consumed within WECC (Western Electric Coordinating Councils) turf.   Electricity generated by PJM doesn't make it to CAISO (California) or ERCOT.

Solar water heat systems - need not be more expensive... but they are.  mostly from profit taking by the manufactures - and smaller production quantities.   Compare the price for an 80 gallon solar hot water tank - with a external flat plate heat exchanger,  or a double lined in-tank heat exchanger... and the price is generally equal or higher than the tankless heater.

I've been there and done it... hands down the solar is more expensive.   In China the hot water is more commonly produced using solar hot water systems -- however that is possible because they take lots of short cuts that most US installers are not allowed to do... China tanks may not  ( optional) use the double lined internal heat exchanger,  the materials are often lower cost/grade and just replaced more frequently.. space isn't generally as much of a problem... and  there tends to be less concern about the looks of the system and the surrounding architecture.

If you go out and look for places to buy solar hot water systems - many of the businesses are no longer  there... unfortunately within the US we are going through another solar hot water bust cycle.  The cause was simply too expensive hardware -- with lower cost solarPV options available.  It actually becomes cheaper and less maintenance to install solarPV (even in offgrid situations) and either dump the excess generation to resistance elements in electric hot water heater,  use heat pump hot water heaters,  or go grid tied.  

I don't believe you can find the parts for a commercially built solar hot water systems with the appropriate industry certifications... for less than perhaps $5000 or $6000.   But for that price you can easily add on 2KW solarPV, then direct heat the water via energy dump, or go grid tied.


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