One advantage is that since the tankless unit does not have a tank, there is no continuous heat (energy) loss from the large volume of stored hot water, as there is with a traditional storage type heater. Typically tankless heaters do not have standing pilot lights like tank type units, saving even more energy. There is no question tankless water heaters are more energy efficient.

Another advantage is that you have virtually unlimited hot water, you will never run out. This could be a double edged sword though, as there is a tendency for humans to use what is available. Some users might end up taking much longer showers for instance, leading to an increase in water and energy usage.

This effect was common back when the government provided large tax credits for installing solar water heaters. Homeowners believing they now had cheap hot water tended to use a lot more hot water than before the solar heaters were installed.

American Heat ADK 16 KW Whole House Tankless Water Heater US $269.00

Noritz SC-201-6M Tankless Water Heater System Control US $264.95

Tankless Water Heater Olympia 18 KW Whole House New US $205.00

American Heat AH-18 Whole House Tankless Water Heater US $391.00

TITAN N-160 SCR-3 Electronic Tankless Water Heater BRAND NEW US $309.99

Rheem RTGL74XP Outdoor 7.4 GPM Tankless Water Heater for Liquid Propane US $699.88

Bosch 1600H LP AquaStar 4.3 GPM Indoor Tankless Liquid Propane Water Heater NIB US $580.00

NIB GE INDOOR TANKLESS GAS WATER HEATER 7.5 MODEL GN75DNSRSA US $649.88

NORITZ 8 GPM INDOOR NATURAL GAS TANKLESS WATER HEATER US $1,999.99

NORITZ 8.3 gpm INDOOR HOME TANKLESS WATER HEATER NATURAL GAS NG NR83-DVC-NG US $1,319.99

NEW NATURAL GAS TANKLESS WATER HEATER 4.23 GPM / 16 L US $297.95

American Heat 16 KW Whole House Tankless Water Heater US $269.00

Noritz N-0751M-DVC (LP) - 9.8 GPM - 199,900 BTU/H Tankless Water Heater Propane US $910.00

Rinnai Tankless Water Heater R75LSIN Interior Natl Gas US $1,125.00

8 Valve kits for Tankless Water Heater LEAD FREE (T) US $590.00

8 Valve kits for Tankless Water Heater (S) US $460.00

8 Valve kits for Tankless Water Heater LEAD FREE (S) US $590.00

8 Valve kits for Tankless Water Heater (T) US $460.00

Rinnai Tankless Water Heater R94LSIN Interior Natl Gas US $1,299.00

Rinnai Tankless Water Heater R75LSIP Interior LP Gas US $1,125.00

Marey® 4.2GPM/16L Natural Gas Whole House ON DEMAND Tankless Hot Water Heater US $296.95

Rinnai Tankless Water Heater R75LSe Exterior Natl Gas US $1,090.00

Rinnai Tankless Water Heater R94LSe Exterior Natl Gas US $1,290.00

Eccotemp 40HI 6.3 GPM LP Intdoor Tankless Water Heater US $429.00

Eccotemp 40H 6.3 GPM LPG Outdoor Tankless Water Heater US $429.00

Eccotemp FVI12-LP 3.4 GPM Gas Tankless Water Heater US $269.00

Eccotemp 40H 6.3 GPM NG Outdoor Tankless Water Heater US $429.00

Rinnai Tankless Water Heater R75LSEP Exterior LP Gas US $1,090.00

Rinnai Tankless Water Heater R94LSEP Exterior LP Gas US $1,290.00

Rinnai Tankless Water Heater R94LSIP Interior LP Gas US $1,299.00

Noritz N-132M-ASME (LP) - 13.2 GPM - 380,000 BTU/H Tankless Water Heater Propane US $2,905.00

NIB Rheem Tankless Water Heater US $580.00

Bosch Tankless Water Heater ES VVT Vertical Vent Kit for AquaStar 2700ES 2400ES US $270.00

Marey Whole House On Demand 4.2 GPM Propane LP Gas 16L Tankless Hot Water Heater US $296.95

New Rheem/Paloma Tankless Water Heater 7.4 GPM Propane Gas Power Vent PTG-74PVP US $799.99

NEW Rheem/Paloma 5.3 GPM Tankless Water Heater Power Vent Propane RTG/PTG-53PVP US $529.95

HHP HH19 Single Shower Tankless Water Heater US $434.12

HHP HH28 Tankless Water Heater Whole House US $704.95

HHP HH12 Single Shower Tankless Water Heater US $412.47

Stiebel Eltron Tankless Water Heater Tempra 12B US $435.00

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A minor advantage that tankless units have over storage units is the size of the footprint. The tankless units take up less space, although I don’t think that is very important to most people.

Obviously there are some disadvantages to tankless water heaters. For one thing, they are much more expensive, and far more complex than a standard water heater. If they require repair it’s likely to be more expensive, and the parts are harder to obtain in some cases. Gas units require a large and more expensive flue, and electric units require very heavy wires because they use so much electricity.

Tankless heaters are typically turned on by a flow switch which turns the heater on when a minimum flow is reached, typically ½ to ¾ gallons per minute. This can be problematic if you need a very small flow of hot water, and can lead to wasting water. Most hot water circulating pumps don’t pump enough water to reliably activate tankless water heaters.

Using a traditional circulating pump will void the warranty on most tankless heaters, since they will cause the heater to turn on and off very frequently and far more than in typical household usage.

One of the biggest problems with the tankless heaters is the fact that they take much longer to get hot water to the fixture than traditional tank type units. You can picture a tankless water heater as a long pipe coiled up over a flame. For the water to get fully hot, it must travel all the way through the pipe. If the water starts out in the middle of the heater for instance, it will leave the heater after only being in the pipe for half the time it would need to reach full temperature. This means that it will take much longer for your water to get hot while you run the faucet waiting for it. It’s pretty clear that this will cause an increase in water being run down the drain, costing the home owner money, wasting one of our most precious resources.

There is however a way to eliminate any of the water from being wastefully run down the drain while waiting for hot water. Use a hot water demand system. A hot water demand system only turns on when hot water is “demanded”. When you are ready for your shower you push a button and the pump sends the hot water from your water heater to your fixture more quickly than if you run the shower at full blast, and the pump shuts off when the hot water reaches it. Thus you save time, water, energy, and money.

Many local water districts offer rebates for demand hot water systems, so check with your local water company, some of the rebates cover the entire cost of a demand system, so in effect, you get a free system!

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