How to Choose Between a Tankless vs. Traditional Water Heater

New water heater in a home in Seattle

If you’re looking to replace your water heater, you might be wondering whether a traditional unit or a tankless heater is the better option. Tankless water heaters are generally more energy-efficient, but they also cost more to purchase and install. This is especially the case if you’re changing from a traditional to a tankless unit since this will require retrofitting the plumbing to the unit. On the other hand, tankless heaters take up less space and don’t have the same risk of leaking as a traditional unit since they don’t store any water.

Tankless water heaters are the preferred choice nowadays. However, there are some situations where a traditional heater still makes more sense. Here is everything you need to know about both units to help you determine which is the better option for your home.

How Tankless Water Heaters Work

Whereas a traditional water heater stores a large volume of hot water inside its tank, a tankless heater only runs when hot water is needed. Often referred to as on-demand water heaters, these units use a heat exchanger that brings the water up to temperature in only a few seconds. The units can run off either gas or electricity. With a gas heater, the unit burns either natural gas or propane to warm the heat exchanger, whereas an electric unit uses electricity to instantly heat a series of coils. In either case, the heat exchanger then instantly transfers the heat to the water as it passes through the unit.

Electric units are usually what is termed a point-of-use heater, which means they only provide hot water to one water source, such as a sink or shower. On the other hand, a gas unit is usually a whole-home heater that can provide hot water to the entire building. Electric heaters have the advantage of being able to provide hot water almost instantly since these units are usually located within a few feet of the water source. With a gas heater, it can take anywhere from a few seconds to a minute or more for hot water to reach the tap. The exact time depends on how far away the water source is from the heater, as well as the temperature of the water coming into the unit and the temperature of the plumbing lines inside the building.

How Much Energy Do Traditional and Tankless Heaters Use

In general, electric tankless heaters are more efficient than gas units. Most gas units will achieve around 80 to 85% efficiency, whereas electric units are usually around 98% efficient. Still, the fact that natural gas and propane tend to cost less than electricity means that the overall energy costs tend to be quite similar with either type of unit.

Compared to traditional water heaters, tankless units use much less energy. This is because a traditional unit constantly uses energy to ensure the water inside the tank remains at a certain temperature. In essence, this means that you’re paying money to heat the water whether you’re using it or not.

According to the EPA, tankless water heaters use around 22% less energy than traditional heaters on average. However, this number can be much greater or lower depending on how much hot water you use in a day. If you use very little hot water on an average day, your savings will be much greater than if you use lots of hot water every day. The EPA estimates that a tankless water heater will use around 40% less energy if you only use 40 gallons of hot water a day, but this could shrink to less than 10% if you use over 80 gallons a day.

Understanding Flow Rates

A tankless water heater can provide an almost limitless supply of hot water, which means you should never again have to worry about running out of hot water like you would with a traditional heater. However, it is vital that whatever tankless unit you choose is appropriately sized for your needs. If the unit isn’t appropriately sized, you may be limited as to how much hot water you can use at one time.

In this case, the most important factor is the flow rate, which is measured in gallons per minute (GPM). To determine what size of unit you need, you’ll need to consider how many different water sources you might need to use at one time and then add up the total water usage.

To make this easier, here are the typical flow rates for various fixtures.

  • Bathroom faucet: 0.5-1.5 GPM
  • Kitchen faucet: 2-3 GPM
  • Shower: 1.5-3 GPM
  • Dishwasher: 2-4 GPM
  • Washing machine: 3-5 GPM

Let’s say that two people in your home typically shower at the same time. In this situation, your tankless heater would need to have a minimum flow rate of around 6 GPM to ensure both people have plenty of water. Still, an even larger unit would be required if you wanted to be able to run your dishwasher and washing machine at the same time. This is an important consideration since the higher the flow rate the unit has, the more expensive it will be.

Factors to Consider When Choosing a Water Heater

Although tankless water heaters are usually the better option, this might not always be the case. For instance, if your home is especially large, you might still want to consider a traditional unit since it could potentially take up to a few minutes for the hot water to reach a sink or shower that’s a long distance away from the heater. In this case, the added water usage from having to leave your tap running for that long can cut into whatever energy savings you get from the tankless unit.

The same can also be true if your home uses lots of hot water every day or you think you’ll need a large volume of hot water at any given time. In this situation, whatever energy you save with the tankless heater may not ever be enough to offset the additional purchase and installation costs. You could avoid this issue by purchasing multiple point-of-use tankless heaters, but this will obviously cost far more than it would to buy and install a traditional unit.

One other factor to consider is the expected lifespan of each type of heater. In most cases, a traditional water heater will only last for around 10 to a maximum of 15 years before needing to be replaced. On the other hand, a tankless heater should easily last for 20 years or more. This is obviously a major consideration since you could potentially end up needing to buy two traditional heaters in the same time span that you would one tankless unit.

Expert Water Heater Service

If you’re looking to replace your water heater, Black Lion Heating & Air Conditioning can help you evaluate your home and your needs to determine whether a traditional or a tankless unit is best. We specialize in the installation, maintenance, and repair of all types of water heaters and have been providing exceptional service to customers in Kirkland and the Seattle area for more than 20 years. Our team also includes certified HVAC technicians who can maintain and repair your home’s heating and cooling systems. For more information on your options for a water heater replacement, give us a call today.