What to Know Before Buying a Tankless Water Heater

This is the first article of a new Q&A interview series, “Ask an Expert,” that will feature a trending topic within our industry. For this first Q&A, Lisa Zollinger, IEI marketing manager, interviewed Bill Ivey, IEI principal consultant, and asked him several questions related to tankless water heaters.

Lisa Zollinger (LZ):How does a tankless water heater differ from a traditional water heater?

Bill Ivey (BI): The traditional tank type water heater utilizes electrical elements or a gas burner to heat, store and maintain hot water at a certain temperature setting. The idea is to store enough hot water to meet the anticipated demand without relying on electrical elements or a gas burner, which are only used to slowly restore the temperature.

A tankless water heater does not store hot water, rather it heats the water as it passes through the water heater in a near instantaneous fashion. This means that the electrical elements or gas burners must have more heating capacity than those for a tank-type heater.

LZ: What are the primary benefits of a tankless water heater?

BI: The primary benefit is energy efficiency, as there is less energy loss. In a tank type unit, heat is lost from the water being stored which is transferred through the tank and into the surrounding space. Tankless heaters are also smaller, can be mounted on a wall and should last longer. Another advantage is, assuming proper sizing, you should never run out of hot water.

LZ: What are the disadvantages of a tankless water heater?

BI: Tankless water heaters are not always well suited for replacement of a tank type since the electrical or gas infrastructure will have to be upgraded to support the instantaneous heating feature. In some instances, this could require increasing the capacity of the service from the utility company. Tankless heaters are also more sophisticated and require a higher level of installation and operational expertise.

LZ: What do I need to know before switching to a tankless heater?

BI: You’ll need to verify available electrical or gas capacity. If you are going with electrical, you need to make sure your house has the additional electrical capacity to operate the tankless water heater. A good electrical contractor can help you determine this and what the cost would be to upgrade. The same applies if you are going with gas, except you need a licensed plumber or a plumbing engineer to help with this.

LZ: Do I need to hire a pro to install a new tankless water heater, or can I DIY it?

BI: This is not a do-it-yourself job, especially if you are replacing a tank-type heater. The electrical wiring or gas piping may have to be upgraded. It may even require upgrading the utility company’s service to the house. Tankless water heating systems are much more sophisticated than a tank-type heater and less forgiving, if not installed just right. Hire a licensed plumber that has experience with tankless water heaters and good reviews.

LZ: How do I properly size a tankless water heater?

BI: I recommend you find a licensed plumber that has experience with tankless water heaters to size it. You can then check it yourself using the manufacturers guidelines or have an engineer do it.

LZ: What other types of water heaters are worth considering?

BI: Heat pump water heaters are becoming more mainstream as manufacturers respond to today’s emphasis on energy efficiency and climate. These are refrigerant based systems like an air-conditioning unit and operate with electrical power. They remove heat from a room or outdoor environment and use it to heat water.

For more information on the pros and cons of tankless water heaters, check out our complete list, 4 Pros and 4 Cons of Tankless Water Heaters. Also, stay tuned for a future article on heat pump water heaters.