Tankless Water Heaters Are Not As Eco-Friendly As We Think

By Justin Horner | July 29, 2016

When tankless water heaters were first introduced to the market, it seemed to be a victory for those who cared about conserving our natural resources. Rather than having to use one of the wasteful traditional water heaters that constantly used energy to keep its tank filled with hot water, tankless offered us a much more eco-friendly option. We would only heat the water as we needed it and not waste energy by heating gallons of water that wasn’t currently being used. However it seems that tankless water heaters are not as eco-friendly as we think.

Wasted Water

The entire selling point of tankless water heaters is that they heat the water when you turn the faucet and not beforehand. This led to less energy being used, a benefit to both the environment and your wallet. Unfortunately neither of those alleged benefits will come to pass for those who use a tankless water heater.

Standard water heaters are described as being wasteful and inefficient. They are known for only being 60% efficient at heating the water in their tanks. That means 40% of the energy used to heat the water is lost. Some of this due to inefficient burners, and the rest due to the gradual cooling of the water stored in the tank over time. By comparison, tankless water heaters are advertised as being much more efficient as they do not have to worry about the water that has already been heated cooling down.

But don’t they?

When you turn the faucet at your kitchen sink, your plumbing begins to send the water to you to use. As it flows through your system, at some point it travels through your water heater. If you’re using a tankless water heater, the heater will detect that water passing it through it needs to be heated. It will begin the process of warming its coils and passing that heat to the water traveling through it. This can take a significant amount of time to reach the proper temperature. During that time the water flowing out of the faucet is being wasted.

The time it can take for the tankless water heater to produce hot water is largely dependent upon the piping you have running through your household. Remember that every time you use heat your water, you are also heating your pipes. This is because as the water travels through your pipes, the heat it gained is being siphoned away by the cold pipes.

How much water is wasted while waiting for it to arrive at the desired temperature is difficult to measure. This is because wasted water is mostly behaviorally driven. Those who are willing to take a cold shower are going to waste much less water than a person who is willing to watch water pour down the drain until their shower is “just right”.

Tank vs. Tankless

The energy efficiency of tank water heaters compared to tankless is not the blow out those selling tankless would have you believe. After factoring in the time it will take a tankless to actually heat the water passing it through it to the desired temperature, the comparison to a tank water heater that always keeps its supply of water hot and ready to use gives only a narrow lead to tankless heaters.

Economically, though tankless claim to save you money on your energy bills that will pay for the cost of the heater over time, this claim is made by leaving out associated costs. There are installations costs, regular service performed by a qualified technician required to stay within warranty, and the initial price tag that are regularly triple the cost of a comparable tank water heater to consider. When these costs are added together, the tankless water heater is far less friendly to your wallet than the tank.

With areas all over the world suffering from water shortages such as the record breaking drought in California, water conservation is a very real concern to consider. Wasted water is a certainty when using a tankless water heater. A tank water heater on the other hand, always keeps the water hot. Since users are not waiting for water to reach the desired temperature, there is very little water wasted when using a tank water heater.

If you are thinking of using a  tankless water heater in order to help conserve resources, then perhaps it is time you reconsider. Tankless water heaters are actually worse for conservation efforts than traditional water heaters. While they may use less energy, tankless heaters waste much more water by comparison. And we are quickly approaching a time, where every drop will count.