For some, installing a tankless water heater system is the most energy efficient and only way to go, but it's not the best for everyone. If you live in a northern climate, very cold ground water can affect the demand and cost efficiency of a tankless water heating system, as can low water pressure.
Fuel type is your first decision - whether you want an electric, natural gas or liquid propane water heater depending of course on availability in your area. And you'll need to confirm that any system you decide to install, meets local building, electrical/gas codes as well as your own in-home compatibility. Next, you'll need to decide on size to meet your family's hot water needs. Most tankless systems are designed to supply enough water based on the number of bathrooms a home has and average use, so you may want to watch for this important detail. Electric systems are the most economical to buy, but may not be the most efficient to operate if natural gas or propane is readily available. Keep in mind that gas heaters will have venting requirements and you may want to consult with your provider to ensure your fuel set-up can support a tankless heater.
Even with the cost of professional installation (recommended) and the initial outlay, a tankless water system will quickly pay for itself, given the lower operating costs. And when you factor in the longer lifespan compared to a tank model, a tankless water heater is a solid investment.
Why it's best: This model offers the best performance and price value for a natural gas, whole-house model that can be installed inside the home. It has ample hot water flow for a typical family home with two or three bathrooms and the ease of installing, though it still needs to be done by a professional, makes it a good choice. With a commercial-grade heat exchanger - it's durable and has a long 12-year limited warranty on the exchanger and 5/1 on parts and labor. Because it's Energy Star compliant, you'll get the best operating cost efficiency and check your state's rebate programs - it may qualify for an Energy Star rebate. This model is also available for liquid propane fuel (R75LSILP) or for installing to the exterior of the home (R75LSENG). See more reviews, photos, prices, and specs
Why it's a best pick: The best choice in an electric model, the Stiebel combines good performance with an affordable price. As for water flow, it's a good size for a family home with two or three bathrooms. Its best feature - you can set the desired temperature, which is nice when you have young children in the home and it will monitor the water to maintain that setting. Stiebel combines German engineering with reliability and a three-year parts warranty to offer consumers tankless water systems they can depend on. See more reviews, photos, prices, and specs
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Why it's a best pick: With 7.4 gallons per minute, there's plenty to go around so you can conveniently draw hot water from more than one source at the same time. Built to last, this Rheem water heater has a 20-year expected life cycle - that's much more than most traditional storage tank models. Designed for easier installation, there are venting options to choose from and this indoor unit is fueled by natural gas. Energy Star compliant, so it may qualify for a rebate in your area and it's a good choice if you're looking for the best energy savings. See more reviews, photos, prices, and specs
Why it's a best pick: You can save a little if your needs are less. Rated for one to two bathroom homes in warm climates or less (1-bedroom) in cold areas, the Tempra-20 is a good choice if your water pressure is not optimum as this unit flows well with less. A slim design so it gives you more installation options and this unit has the same handy temperature control features as the Tempra-29. See more reviews, photos, prices, and specs
Why it's a best pick: The Bosch is a good choice if liquid propane gas is your fuel of choice for heating hot water, your needs are smaller and your normal water pressure is on the lower end. Though hot water flow is not as great as other units, this smaller system may be easier to install for some and consumers find it adequate when they're not running several hot water appliances at once. See more reviews, photos, prices, and specs
I Have the Bosch Aquastar 125FX Propane Tankless Water Heater and i can say its a very efficient machine and very easy to install
About "Even with the cost of professional installation (recommended) and the initial outlay, a tankless water system will quickly pay for itself, given the lower operating costs." is great sentence why I prefer to choose use tankless model.