Which is the best tankless water heater will depend on who is purchasing it and for what application. The best tankless water heater for your cabin in the mountains’ will not be the best one for your 4,500 square foot home in Florida. It may be a different model for the same home in Colorado.
For some people the best tankless hot water heater will be the one that saves the most energy, or the one with the least maintenance, or even the one that is the least expensive. For others, the ability for the tankless heater to work with a hot water circulating system, or the ability to deliver very low flow rates would be the best tankless water heater.
If you are looking for a point-of-use water heater you will have an entirely different set of critera than if you are in need of a whole-house unit.
Some tankless water heaters are designed for mounting indoors, and some are designed for mounting outdoors on an external wall. The outdoor units usually come with an internal heater to protect against freezing… very important in many areas. If your heat exchanger becomes damaged due to freezing temperatures, the warranty will not cover it.
First, be certain you are better off with a tankless unit than a standard storage heater. There is little similarity between tankless and storage type heaters. About the only thing they have in common is they consume similar fuels and produce hot water.
Energy Savings
I suspect that one of the big reasons people convert from tank type heaters to tankless heaters are to be green and reduce their energy bills while reducing their carbon footprint. Further I would think that the primary reason to save energy is to save money. Let’s take a look at the savings from a tankless heater over a conventional tank type heater.
Tankless water heaters are said to be more energy efficient than standard tank type water heaters primarily because they do not have standby losses. You can figure out a ball park figure for standby losses from heat leaking out of the tank full of water with the following formula:
H = A (T1-T2)/R
H = Heat loss in Btu/hr
A = Surface area in square feet
T1 = Hot water temperature in Degrees Fahrenheit
T2 = Air temperature in Degrees Fahrenheit
R = R-value of the insulation in ft2hrF/btu
My assumptions:
Tank dimensions: 60 inches tall by 22 inches in diameter.
Area = 36.5 square feet.
R value = 16
Hot water temperature = 140 degrees
Ambient Air temperature around heater – 55 degrees average over a year
H = 36.5 * (140 – 55)/16 =194 Btu/hour
Btu/month = 194*24*30 = 139,680 Btu = 1.39 Therms per month
Assuming $0.60 per therm your standby heat loss from the tank will cost you about 83 cents a month.
Although the standby losses are a little higher for colder climates, standby losses will never add up to a huge amount of money. You might be better off buying a high efficiency tank type water heater.
Endless Hot Water
It would seem to me that the next most common reason for going tankless would be for the endless hot water. In my opinion this would be the most realistic reason for switching to tankless. Running out of hot water is a real pain in the shower.
As long as you choose a tankless heater that is big enough for your needs you will get your unlimited amount of hot water no matter which brand you choose. There isn’t one tankless brand that stands out above the rest as far as I can see.
To learn more about proper sizing of a tankless hot water heater: Sizing a tankless water heater
Here is an article where I compare Navien, Rinnai, Takagi, and Nortiz brand tankless water heaters. Compare Tankless Water Heaters.
Reliability
For some people the best tankless water heater is the one that is the most reliable. Tankless water heaters are highly complex machines, unlike their tank type cousins. They monitor things like inlet water temperature and flow, outlet temperature, exhaust temperature, and gas pressure and flow. They have one or more onboard computers to makes sense of all the data streaming in from the sensors and control the burners and some models even control the flow of water through the unit.
Needless to say there are a lot more things to go wrong. The most important thing to consider when choosing a tankless heater for your home is the installation. Improper installation is the most common cause for tankless water heater problems.
An improperly installed heater can wait years before the problems show up. The heater may work fine with small draws, but when a large draw is required suddenly there is a problem. If the heater requires the condensate from the flue to be drained, and the installation isn’t done right, the condensate can drip on the heat exchanger and after a couple of years suddenly the heat exchanger goes out due to corrosion from the condensate. This will not be covered by your warranty.
More about tankless water heater installation: Tankless Water Heater Installation
My advice is to find a local plumbing company that will stand behind their water heaters, have professional factory trained installers, and can refer you to some happy customers. Get the right size unit from the right local supplier and you will have found the best tankless water heater for your needs.
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