Traditional water heaters usually have higher energy costs, require large space and have a life of 10 to 15 years. Tankless water heaters solve these problems and are hence becoming very popular. If you want to buy a tankless water heater, take some time to know the technology, fuel type, flow rate, energy efficiency, installation costs, maintenance and warranty. Once you know the important features, compare the costs of at least ten companies and shortlist five and make a final decision.

Checklist of features to compare before buying tankless water heaters
Once you know how much warm water you need and the fixtures you have (bathroom, sinks, washers), you can look for water heaters with appropriate flow rates. If you have a higher requirement and buy a water heater with a lower flow rate, you have to face a slow supply of hot water if multiple people use it simultaneously. Other features that you need to compare are as follows:

• Fuel type: Natural gas, propane and electricity
• Flow rate: The maximum flow of hot water at gallons per minute (GPM)
• Power Input in British Thermal Unit
• Energy-certified rating
• Venting
• Condensing or non-condensing
• Your family’s hot water requirements
• Price
• Installation costs
• Warranty

1. Rinnai RU199iN Tankless Water Heater
   The Rinnai RU199iN Tankless water heater has an 11-Gallon-per-minute flow rate and can satisfy the hot water requirements for seven fixtures. Its thermal input is 199,000 BTU, and can satisfy the requirement for a family. It is Energy-Star certified, and its energy efficiency is between 93 and 96 percent. It works on natural gas and on the condensing feature, which allows the heater to remove the heat from the exhaust and release it through the ventilation. It is a wall-mounted unit. It needs the help of professionals for installation. It has different warranty levels on the device, parts, labor, and heat exchanger. It costs $1854.74.
2. Stiebel Eltron Tempra 36 Plus
   Stiebel Electron Tempra 36 plus runs on electricity has an impressive 99% energy efficiency rating. It operates silently. It has a flow rate of 7.5 GPM and 92,000 BTU power input. It has an advanced flow control feature that helps maintain uniform water temperature. It does not require venting. It has present temperature buttons digital displays and ensures a continuous warm water supply. It costs $692.44. (prices may vary on different e-commerce sites)
3. Rheem RTEX -24 240V Tankless Water Heater
   Rheem has been making water heaters for about 100 years. The Rheem 240V is an electric tankless water heater that continuously supplies hot water on multiple fixtures. It has features including external thermostat control and durable copper heating elements. It has a 99 percent efficiency rating. It has a 4 GPM maximum flow rate and a 45,000 BTU maximum power input. It is ideal for a family of two looking for a low-cost tankless water heater. It is not energy star certified. It costs $299.
4. Noritz EZ111 EZ series
   Noritz’s EZ111 series of tankless water heaters have a 25-year limited warranty. It uses liquid propane and has an energy efficiency rating of 97%. It has a flow rate of 11.1 GPM and 180,000 BTU power input. It is a direct vent model and is compatible with ½ gas pipe. It comes with a remote thermostat, adjustable temperature features, and is wall-mounted. It needs professional installation. It can be connected to Wi-Fi. It costs $1,585.
5. Takagi T-H3-DV-N
   Takagi T-H3-DV-N is a high-efficiency indoor tankless water heater that uses natural gas. It has multiple safety features, including freezing, overheating, surge protection, and troubleshooting. It has a 10 GPM and 199,000 BTU power input. It is compact, saves space, and supplies continuous hot water on demand. It is a direct vent and a condensing model. It can work efficiently up to 10,100 ft altitude. It can conveniently supply warm water for four bathrooms in cold climates. It is Energy-Star certified. It is ideally suited for single residences or small restaurants. The cost is $1,299.