Tankless water heaters are also known on demand or instant water heaters; heating water only when required. In these types of heaters, the type of gas used may be either propane or natural gas and hence one should always verify the supply available before purchasing the heater.
Some popular models include Bosch Aquastar 2400ES Gas Tankless Water Heater, GE Indoor Tankless Gas Water Heater Model GN94DNSRSA and Rheem Tankless Water Heater RTG-74PVN-1, Indoor Use.
One has to carefully evaluate their need and usage along Best propane tankless with the cost factor before purchasing them considering that this is one time investment as the tankless water heaters have a life expectancy of about 20 years.
Pros for Tankless Gas Water Heaters
Saves energy. The unit operates when there is a demand for hot water, which can reduce its energy cost by about 25% annually. Best performance comes from gas units, as electric units are not Energy Star-rated.
High efficiency. The most efficient storage tank has an energy factor of about .67, but according to Energy Star, some tankless units have energy factors as high as .95.
Unlimited hot water. Can deliver hot water for hours, not limited by tank capacity.
Constant temperature. Doesn’t get cooler as hot water runs out of the tank. If a unit is sized properly, a gas tankless heater can deliver a continuous supply of water at a preset temperature at a rate of typically 2 to 5 gallons per minute.
Compact size. Can be mounted on wall, freeing up floor space.
Cons for Tankless Gas Water Heaters
More expensive. Tankless units cost about twice as much as traditional storage tanks. A typical unit may cost about $700 to easily top $1,500.
Installation is expensive. Besides high product cost, installation and the necessary piping can be pricey. Good venting is also required which can be expensive.
Retrofit is pricey and complicated. Retrofitting a home with a tankless unit can be a complicated process as compared to traditional storage tank and may cost as high as $3,000.
Longer delay by a few seconds before hot water starts flowing. This can make short uses like washing of hands impractical. Water is also wasted while waiting for the hot water to flow. Placing the heater close to the point of use will reduce this problem.
Limited heating capacity. Might not heat water to high enough temperature in winter, depending on required flow rate of water. Some models have a specified minimum inlet water temperature (example: 60 degrees Fahrenheit).
Maintenance is required. Valves may need cleaning or lubrication every year, replacement every few years.
Needs high gas pressure. Gas pressure in some locations can be too low. This needs to be checked with a manometer.
Warranty terms can be strict. Warranties can be voided by installing without licensed plumbers, installing the heater in the bathroom, not doing annual maintenance.
Many of the points above can be found in the instruction manuals of tankless gas heaters. Homeowners should check the instruction manuals before buying, to avoid unpleasant surprises.