Which Uses More Energy: a Tank or Tankless Water Heater?


Tanked water heaters are more commonly found in homes as they are the conventional option for getting hot water.

However, over the last few decades, tankless water heaters are becoming a rapidly spreading trend.

This is because tankless water heaters are known to save resources like energy.

But is there really a noticeable difference in the amount of energy used? Let’s find out.

Which uses More Energy: a Tank or Tankless Water Heater?

Tank water heaters tend to have a standby-loss of energy. This happens because energy is wasted to keep the tank full of hot water at all times.

This factor is eliminated with the tankless design as water is only heated as and when required. The energy saved by this design is of a significant amount.

By saving on energy, tankless water heaters end up saving money as well. While these products may cost more initially, they can cut down utility bills by 25%.

Through lower operation costs, regular use of these heaters compensates economically for the higher product prices.

The difference in energy efficiency depends on how much water is used but always favors tankless models. For a water usage of 41 gallons or less, the energy efficiency can be 24-34% more than that of tanked heaters.

A higher usage of about 86 gallons a day achieves an efficiency higher by 8-14%. This difference can be made 27-50% if separate heaters are installed for each point of use.

To demonstrate the difference in energy usage, we compared the Energy Efficiency Factor (UEF) of the most popular tank and tankless water heaters. As the numbers clearly show, this difference is huge.

The Rheem Performance Natural Gas 40-Gallon tank heater has a UEF of 0.58.

Similarly, the Sure Comfort 40-Gallon tank heater has a UEF of 0.62.

In fact, the maximum efficiency from a conventional storage-tank water heater does not exceed 0.70.

Tankless water heaters, on the other hand, have much better efficiency.

For example, the Rheem Performance Platinum Natural Gas tankless heater has a much higher UEF of 0.94.

The Takagi TK-199X3P and Rinnai V75iNl have a UEF of 0.93 and 0.82 respectively.

Thus, in terms of energy efficiency, tankless water heaters are far superior to tank ones. This efficiency translates into money savings too, but how much, that is based on water usage.

About Sharon Martin

Sharon is a woman of many talents. She loves to work on power tools and provides handyman services. Sharon has expertise with both woodwork and metalwork, so she's always prepared for any job! When not working, Sharon can be found listening to country music or spending time with her cats.