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Article Originally Posted on WaterHeaterStore.co

For immediate, near-unlimited hot water, tankless water heaters are by far more efficient than their big brothers – tank-based water heaters. Tankless systems heat water on demand, as opposed to tank systems that heat water and store it in a reservoir. Tank-based systems are subject to having to re-heat the water if it cools and also has a limited supply of hot water since they’re not designed to heat water quickly.

Over the last few years, tankless systems have evolved, and a lot more options are available. Depending upon your needs and budget, tankless water heaters can be integrated into specific appliances – washing machines and dishwashers, for example – or into full structure hot water supply systems.

Types of Tankless Water Heaters

Tankless water heaters come in several shapes, sizes, and types. The primary consideration for most people is the fuel type. The more common formats for tankless systems are:

Electric Tankless Water Heaters 

  • They can be plugged into a 110/220 volt outlet or tied directly to a power supply. Throughput of hot water is less than gas-based tankless water heaters but can handle most demands so long as multiple sources are not drawing hot water.

Propane Tankless Water Heaters

  • Great for remote locations and short-term solutions like camping or rural installations. High throughput of hot water makes these tankless water heaters a solid choice for complete water heating systems.
  • Natural Gas Tankless Water Heaters are highly efficient and ideal for larger installations that need lots of hot water fast. These systems have a high throughput of hot water and can be installed in a single location in a facility or home to supply all hot water.

Advantages of Tankless Water Heaters

The most significant advantage of tankless water heaters is that you get an unlimited supply of hot water, so long as too many sources are not drawing hot water at the same time. For example, running a shower and a washing machine may max out your tankless water heater’s capacity.

Tankless water heaters are also incredibly efficient when compared to tank-based systems. Instead of heating water and reheating when it naturally cools, tankless water systems only heat water as needed. And you can tune the tankless water heater system to only heat up the water to the ideal temperature.

Lastly, there is no downtime for hot water. Because you get hot water on demand, you don’t have to wait like you would if you ran out of hot water with a tank-based water heater.

Applications for Tankless Water Heaters

The typical tankless water heater system is a single unit that provides hot water for an entire structure. This is fine for buildings where hot water is needed intermittently. If you need lots of hot water to multiple sources at the same time, you have other options.

For those installations that require lots of hot water to multiple sources – such as a restaurant where dishwashers, washing machines, and sinks may all need hot water at the same time – installing smaller tankless water heaters at each appliance is an ideal solution. This means the appliance has all the hot water it needs, the tankless water heater can be set to the ideal temperature – dishwashers like VERY hot water while you might scald people at a sink using the same hot water supply. Simply install smaller tankless water heaters at the hot water supply point for each appliance or where multiple appliances draw hot water.

Considerations for Tankless Water Heaters

The two big decisions are typically fuel source, and hot water throughput needs. If you don’t need high throughput, electric tankless water heaters are an ideal solution because of cost, lack of venting requirements, and ease of installation. A gas tankless water heater may be required high throughput environments.

When you are considering a tankless water heater solution, reference this handy chart for determining whether your tankless water heater can handle max capacity:


Normal Rate of Hot Water (Gallons per Minute/gpm)

Bathroom Sink Bathtub Shower Kitchen Sink Dishwasher
Flow Rates 0.5 2.0 – 4.0 1.5 – 3.0 1.0 – 1.5 1.0 – 3.0

Table of Typical Hot Water Flow Rates