How Do Tankless Water Heaters Work?

One of the most widely advertised but ultimately misunderstood new technologies is the tankless water heater. While they were first heralded as a simple replacement for older standby tank water heaters, they’re a little more complex than that. You may see the best results from combining both styles of water heaters in the same home, or you may simply need to invest in more than one unit to get the heat you want. Find out how tankless water heaters work and how to get the most out of them for your investment.

The Basics of Tankless Water Heater Design

Standby or Tank Unit

The first water heater design that homes came to rely on was known as a standby or tank unit. A relatively large water tank held between 20 and 150 gallons of water at once, heating it constantly to a specific temperature. This water was sent to any hot tap opened in the house, and new water that flowed in would be heated by the element at the bottom of the tank. While this provided a specific amount of hot water, it would eventually run out and leave someone showering in cold water.

Tankless Water Heater

Tankless water heaters aim to reduce the shock of running out of hot water and how much energy is wasted keeping water heated when it’s not needed. Instead of keeping water hot at all times of the day and night, these devices only heat water on-demand. A small amount of water flows into the heater, usually half a gallon or so at a time, and it is heated very quickly before flowing out again. Depending on the size of the tankless water heater, it’s possible to produce up to 3 gallons of fully heated water per minute. This meets even the highest showering and bathing demands. Since the water heater continuously produces more hot water, there’s no sudden drop-off when a tank is suddenly depleted.

Benefits of Going Tankless

Switching to at least one or two tankless water heaters in your home reduces energy use in many cases. Since less water is held at a standby temperature when needed, electricity or gas is saved. You can find tankless units to match the energy source you already use for water heating, making it easy to switch over. Many homeowners with a lot of demand in certain bathrooms or kitchens also find they don’t run out of hot water after adding high-capacity tankless units. These water heaters hold less water, so they don’t create such a flooding or leaking risk as standby units do. Finally, they’re often easier for plumbers to maintain because they tend to be installed under the sink or next to the fixture relying on them.

Types of Tankless Water Heaters

Tankless water heater installed on thw wall

Of course, there’s more than one type of tankless water heater. The first category to consider is the fuel type. Many units are electric only, but some may require a higher voltage than your bathroom or kitchen currently features. Gas-powered tankless water heaters are also popular and tend to offer more on-demand heating capacity. However, they need venting and cost more to install. Each water heater must also be sized to the fixture or fixtures it serves. Add up the average flow in gallons per minute to figure out how many fixtures can be run from each water heater you’re considering. A 2 GPM unit may supply multiple faucets just fine but only a single shower.

Who Should Make the Switch?

Busy families and individuals who aren’t home for most of the day will benefit the most from switching to a tankless water heating system. By eliminating the need to keep water hot all day and night when it’s only used in the mornings and evenings, serious savings are likely to be noticed from the first month of use. People who stay at home all day and use hot water throughout the day are less likely to benefit as much financially. But they may still enjoy the convenience of having more hot water available on demand.

Sizing a Tankless Water Heater

It’s not enough to simply add up water demand for a tankless water heater and install a unit. Consider the incoming groundwater temperature as well before assuming a particular unit can overcome a certain heating gap. For example, many cities supply water at a steady 50 or 45 degree F temperature. To bring water up to 100 degrees F for a comfortable bath, the water heater you install must offer at least a 50-degree increase at on-demand rates. Buying a water heater that only offers a 20 or 30-degree increase at standard flow rates will disappoint you in areas with colder groundwater.

Don’t expect a single tankless water heater to handle the whole house. Instead, aim for one unit per bathroom with a tub or shower and another in the kitchen. Smaller appliances like sinks may be covered with a single centrally located unit instead. Of course, laundry rooms will need their own tankless water heaters as well. By combining a set of smaller units, you may be able to save on energy costs in the long run while enjoying a steady flow of hot water.

While do-it-yourself projects can be fun and fulfilling, there is always a potential for personal injury or property damage. We strongly suggest that any project beyond your abilities be left to licensed professionals such as electricians, plumbers, and carpenters. Any action you take upon the information on this website is strictly at your own risk, and we assume no responsibility or liability for the contents of this article.