How Tankless Water Heater Works: A Quick Guide for Homeowners

How Tankless Water Heater Works

In recent years, tankless water heaters have gained popularity among homeowners looking for a more efficient and cost-effective way to heat their water supply. These innovative devices work differently from traditional water heaters, providing on-demand hot water without storing it in a tank, translating to both energy and space savings. But how tankless water heater works?

A tankless water heater relies on either an electric element or a gas burner to heat cold water as it passes through the unit. As soon as you turn on a hot water tap, the water flows into the heater and is rapidly warmed up, delivering near-instant comfort at a consistent rate. This powerful technology prevents wasted energy, as the unit only operates when hot water is required, unlike traditional tank water heaters that continuously reheat stored water even when not in use.

The efficiency of a tankless water heater is worth noting, as most units can provide 2 to 5 gallons per minute of hot water. While this may be sufficient for single or smaller homes, larger households might consider installing multiple units to cater to simultaneous hot water demands.

Tankless Vs Traditional Water Heaters

Space and Waste Reduction

Tankless water heaters are compact and take up less space compared to storage tank heaters. This can be a significant advantage for homeowners with limited space available. Moreover, when a storage tank heater reaches the end of its lifespan, the large tank ends up in a landfill, contributing to waste. On the other hand, tankless water heaters have fewer materials that need disposal, reducing their environmental impact.

Energy Efficiency and Savings

  • Energy Efficiency: Tankless water heaters only heat the water when it’s needed, as opposed to storage tank heaters that keep a large amount of water hot at all times. This leads to higher energy efficiency and potentially lower energy bills.
  • Savings: Although tankless water heaters tend to have a higher upfront cost (up to $1,150) compared to traditional tank heaters (around $570 to $600), they can save a household around $100 per year, depending on their efficiency and how much hot water is used.

Lifespan and Convenience

  • Lifespan: Tankless water heaters generally last longer than storage tank heaters, providing savings after roughly six years.
  • Convenience: Tankless water heaters deliver hot water at a rate of 2-5 gallons per minute, providing a constant flow, while storage tank heaters may run out of hot water depending on demand. Additionally, gas-fired tankless water heaters produce higher flow rates compared to electric ones.

Overall, the choice between tankless and traditional water heaters depends on a homeowner’s priorities. Factors like available space, hot water usage, and long-term savings should be considered when deciding on the best option for a household.

How Tankless Water Heaters Work

How Tankless Water Heater Works

Heating Process

Tankless water heaters work by using an electric element or gas burner to heat the incoming water as it travels through a pipe to the unit. This method provides a near-endless supply of hot water without the need for a storage tank. When a hot water tap is turned on, cold water runs through a pipe to the unit, and the power source (electricity or gas) heats the water almost immediately.

Flow Rate and Gallons per Minute

The flow rate of tankless water heaters is generally measured in gallons per minute (GPM). These heaters can deliver a constant flow of hot water ranging from about 2 to 5 GPM. This flow rate depends on various factors such as the size and capacity of the heater, and it may vary with temperature changes. Keep in mind that multiple simultaneous hot water demands might affect the flow rate and possibly exceed the heater’s capacity.

Temperature Control

Tankless water heaters are equipped with a temperature sensor and thermostat, which work together to regulate the temperature of the water. The sensor detects the incoming groundwater temperature, and the thermostat adjusts the power source accordingly to maintain the desired hot water temperature. This allows for consistent, on-demand hot water supply and added user comfort.

In summary, tankless water heaters provide an efficient solution for hot water supply by heating incoming water almost instantly and maintaining the desired temperature. By eliminating the need for a storage tank, these heaters save energy and offer cost-saving benefits in the long run.

Types of Tankless Water Heaters

Tankless water heaters primarily come in two different types: gas and electric. Each has its own set of advantages and trade-offs. In this section, we will discuss the features and differences between gas and electric tankless water heaters, to help you make an informed choice.

Gas Water Heaters

Gas tankless water heaters use natural gas or propane as a fuel source to heat the water. Here are some key points about these heaters:

  • They typically have a higher flow rate than electric models, allowing them to provide hot water to multiple fixtures simultaneously.
  • Gas-powered units are often more energy-efficient than electric heaters, which can lead to long-term cost savings on energy bills.
  • Installation usually requires access to a natural gas or propane line, and proper ventilation is essential for safety.
  • Gas tankless heaters tend to have a higher upfront cost compared to electric models but may have lower long-term costs due to energy savings.

Natural Gas

Natural gas is the more common fuel source for gas tankless water heaters. It is typically less expensive and more widely available compared to propane. Some advantages of natural gas include:

  • It burns cleaner, producing fewer emissions and less impact on the environment.
  • Natural gas heating systems generally have a longer lifespan and are more durable compared to propane systems.
  • Gas prices for natural gas are generally more stable, making it a more predictable energy source in terms of cost.

Electric Water Heaters

Electric tankless water heaters heat the water using electric elements. Here are some noteworthy points about these heaters:

  • They require no access to a gas line, making them a more versatile option for installation.
  • Electric models tend to be smaller and easier to install compared to gas heaters, which may save on initial installation costs.
  • These heaters generally have lower upfront costs than their gas counterparts.
  • Electric tankless heaters are not as energy-efficient as gas models and may increase your electricity bill.

In summary, the choice between gas and electric tankless water heaters will largely depend on individual preferences, access to fuel sources, and priorities concerning energy efficiency and installation costs.

Selecting the Right Tankless Water Heater

Sizing and Capacity

When choosing a tankless water heater, it’s important to consider the size and capacity of the unit. Start by calculating the maximum gallons per minute (GPM) you’ll need during peak usage. To do this, add up the GPM of each fixture in your home (e.g., shower, sink, washing machine) that might be in use at the same time. Next, consider the required BTUs (British Thermal Units) needed to heat the water to your desired temperature. Keep in mind that a higher BTU rating will result in more heat output and thus higher efficiency.

Cost and Energy Efficiency

Tankless water heaters vary in cost and energy efficiency. Gas-fired units can range from $170 to over $2,000, while electric heaters can cost between $90 and $900. High-output heaters tend to be more expensive but can supply hot water for multiple fixtures concurrently. In terms of energy efficiency, using a tankless water heater may result in savings on your utility bills. Installing low-flow showerheads or reducing hot water usage can further enhance these savings.


Before purchasing a tankless water heater, consult with a professional plumber to ensure proper installation. First-time installation costs can be higher than a simple tank replacement, but the benefits include a more efficient and reliable hot water supply.


There are several reputable brands to consider when selecting a tankless water heater. Bosch is a well-known manufacturer that offers a variety of on-demand water heaters to suit different needs and budgets. Be sure to research and compare various brands to find the optimal solution for your specific hot water requirements.

By taking the time to consider factors such as sizing, cost, energy efficiency, installation, and brand reputation, you can choose the right tankless water heater for your needs, ensuring a near-endless supply of hot water and greater convenience in your home.

Maintenance and Common Issues

Mineral Buildup and Descaling

Tankless water heaters are highly efficient, but they may experience mineral buildup over time due to the continuous flow of water through them. These mineral deposits can create blockages and reduce the overall efficiency of the heater. To maintain optimal performance, periodic descaling is recommended. Descaling involves removing these mineral deposits through a flushing and cleaning process. Typically, it is advised to perform descaling at least once a year, although the frequency can vary based on the hardness of the water in your area.

Timer and Front-Facing Panel Issues

Another common issue that may arise with tankless water heaters is related to the timer and front-facing panel. The timer is a crucial component of the heater, as it manages the distribution of hot water with energy efficiency in mind. If the timer fails or malfunctions, it can lead to inconsistent hot water supply or even total system shutdown. It’s essential to have the timer checked and repaired by a professional as soon as a problem is detected.

The front-facing panel, also known as the control panel, allows users to adjust the settings of the heater and monitor its performance. Issues with the panel can include unresponsiveness, inaccurate readings, or total malfunction. In such cases, it is essential to consult with a professional to diagnose the problem and determine if the panel needs to be repaired or replaced.

To prevent these common issues and maintain your tankless water heater’s efficiency, it is essential to follow regular maintenance procedures, such as cleaning, checking, and adjusting settings as necessary.

  • Regular descaling to remove mineral buildup
  • Check and repair timer, if necessary
  • Monitor and maintain the front-facing panel’s functionality

Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top