Electric vs Gas Tankless Water Heater [2024]

For homeowners considering an upgrade, the ongoing debate of electric tankless water heater vs gas models often surfaces, presenting a complex decision. Energy efficiency standards, such as those promoted by the Department of Energy (DOE), significantly influence the long-term operational costs of both systems. Brands like Rinnai specialize in gas tankless solutions, while companies such as Stiebel Eltron offer advanced electric options, each presenting distinct installation requirements. Furthermore, local climate conditions in areas like California can drastically affect the performance and cost-effectiveness of either an electric tankless water heater vs gas unit.

Tankless Water Heaters: A Modern Solution for On-Demand Hot Water

Tankless water heaters, also known as on-demand water heaters, represent a significant shift in how homes and businesses access hot water. Unlike traditional tank water heaters that continuously heat and store a large volume of water, tankless models heat water only when needed.

This fundamental difference offers several compelling advantages. These advantages include increased energy efficiency, space savings, and a virtually endless supply of hot water. As a result, tankless water heaters have witnessed a surge in popularity, becoming a sought-after upgrade for those seeking modern and efficient solutions.

The Rise of On-Demand Heating

The appeal of tankless water heaters lies in their ability to eliminate standby heat loss, a common inefficiency in traditional tank systems. With a traditional tank heater, energy is constantly expended to maintain the water temperature within the tank, regardless of whether hot water is being used.

Tankless heaters bypass this issue entirely. By heating water only when a hot water tap is opened, they drastically reduce energy waste.

This makes them particularly attractive to environmentally conscious consumers and those looking to lower their utility bills.

Electric vs. Gas: A Critical Comparison

This article focuses on a detailed comparison between electric and gas tankless water heaters. Both types offer the core benefit of on-demand hot water, but they differ significantly in their heating mechanisms, performance characteristics, installation requirements, and long-term costs.

Understanding these differences is crucial for making an informed decision. This article aims to provide you with the information necessary to select the tankless water heater that best aligns with your specific needs and circumstances.

The Importance of Informed Decision-Making

Purchasing a water heater is a significant investment, and choosing between electric and gas tankless models requires careful consideration. Factors such as:

• hot water demand
• energy source availability
• budget constraints
• local building codes

These all play a vital role in determining the optimal choice.

By thoroughly evaluating these factors and understanding the nuances of each type of tankless water heater, you can ensure that your investment provides years of reliable and efficient hot water. This guide will empower you with the knowledge to make a confident and well-informed purchase.

Core Functionality: Electric vs. Gas Heating Mechanisms

The defining characteristic that separates electric and gas tankless water heaters lies in their fundamentally different approaches to heating water. Understanding these mechanisms is key to appreciating their respective strengths and weaknesses.

Both types achieve the same outcome—providing hot water on demand—but their internal processes and energy sources differ considerably.

Electric Tankless Water Heaters: Direct Electrical Heating

Electric tankless water heaters employ electrical resistance to directly heat the water flowing through them. This process relies on heating elements, typically made of nichrome or similar resistive materials.

When a hot water tap is opened, cold water flows into the unit. This flow activates the system, sending electricity to the heating elements.

As the water passes over these energized elements, it is rapidly heated.

The simplicity of this direct heating approach contributes to the compact design of electric tankless heaters.

Flow and Temperature Sensors: Precise Control

Flow and temperature sensors play a vital role in the operation of electric tankless water heaters.

The flow sensor detects when water begins to move through the unit, signaling the system to activate the heating elements.

Temperature sensors continuously monitor the water temperature, providing feedback to the control system.

This feedback loop allows the unit to precisely regulate the amount of electricity supplied to the heating elements.

This regulation ensures that the water is heated to the desired temperature, preventing overheating or inadequate heating.

Gas Tankless Water Heaters: Combustion-Based Heating

Gas tankless water heaters utilize a combustion process to heat water. These units burn natural gas or propane to generate heat, which is then transferred to the water.

The core components of a gas tankless heater include a heat exchanger and a gas burner.

When hot water is needed, the burner ignites, and the resulting flames heat the heat exchanger.

Cold water flows through the heat exchanger, absorbing the heat from the combustion process.

This rapidly raises the water's temperature to the setpoint.

Venting Systems: A Critical Safety Requirement

A critical aspect of gas tankless water heaters is the necessity of a venting system.

The combustion process produces exhaust gases, including carbon dioxide, water vapor, and potentially dangerous carbon monoxide.

These byproducts must be safely vented to the outside to prevent indoor air pollution and health hazards.

The venting system typically consists of specialized pipes that carry the exhaust gases away from the unit and out of the building.

Different venting options exist, including conventional and direct vent systems, each with its own installation requirements.

Flow and Temperature Sensors: Similar Role, Different Context

Like electric models, gas tankless water heaters also rely on flow and temperature sensors for optimal operation.

The flow sensor detects water flow and triggers the ignition of the gas burner.

Temperature sensors monitor the water temperature and provide feedback to the control system.

This feedback loop adjusts the gas supply to the burner.

This ensures that the water reaches the desired temperature while maximizing energy efficiency.

Carbon Monoxide: A Serious Safety Concern

It is imperative to emphasize the potential for carbon monoxide (CO) production with gas tankless water heaters.

CO is a colorless, odorless gas that is highly toxic.

Incomplete combustion of natural gas or propane can lead to elevated CO levels.

Proper ventilation is essential to prevent CO buildup and protect the health of occupants.

Regular inspection and maintenance of the venting system are crucial to ensure safe operation.

CO detectors should be installed in the vicinity of the water heater as an added safety measure.

Features and Technologies: Similarities and Unique Aspects

Beyond their core heating mechanisms, electric and gas tankless water heaters share several features and technologies designed to enhance user experience, improve energy efficiency, and prolong the unit's lifespan. However, certain models incorporate unique features that cater to specific needs or provide added convenience.

Understanding these commonalities and unique aspects is essential when evaluating the various options available on the market.

Common Features in Tankless Water Heaters

While electric and gas tankless water heaters differ in their energy source and heating method, manufacturers often incorporate similar features to improve performance and user control.

Digital Control Panels: Precise Temperature Management

Most modern tankless water heaters, regardless of fuel type, feature digital control panels. These panels allow users to precisely set the desired water temperature, typically within a range of 100°F to 140°F (38°C to 60°C).

Digital controls offer greater accuracy and convenience compared to the analog dials found on older models.

The ability to set a specific temperature minimizes energy waste by preventing overheating and ensuring water is heated only to the required level. Digital displays also often provide diagnostic information, alerting users to potential issues with the unit.

Modulating Technology: Enhanced Energy Efficiency

Modulating technology is a significant advancement found in many tankless water heaters.

This technology allows the unit to adjust its heating output based on the demand for hot water. Instead of operating at full capacity regardless of the flow rate, modulating units can reduce their energy consumption when only a small amount of hot water is needed.

For example, when a user is only washing their hands, the heater reduces the power consumption.

This results in considerable energy savings over time.

The level of modulation varies between models, with some offering a wider range of adjustment than others.

The greater the modulation range, the more efficiently the unit can operate under varying demand conditions.

Scale Prevention Technology: Combating Hard Water Issues

Hard water, characterized by high mineral content (primarily calcium and magnesium), poses a challenge for all water heaters. Mineral buildup, or scale, can reduce efficiency, restrict water flow, and ultimately damage the unit.

To combat this issue, many tankless water heaters incorporate scale prevention technology. These technologies vary in their approach, but common methods include:

• Electronic Descaling: Employs electronic fields to disrupt mineral crystallization, preventing scale formation.

• Physical Filters: Installed inline to physically remove mineral particles from the water before they enter the unit.

• Specialized Coatings: Applied to heating elements or heat exchangers to minimize mineral adhesion.

While these technologies can mitigate the effects of hard water, it's important to note that they may not eliminate the need for periodic descaling maintenance, especially in areas with extremely hard water.

Unique Features of Select Tankless Water Heaters

In addition to the shared features, certain tankless water heaters boast unique functionalities that set them apart. These features are often model-specific and cater to particular needs or preferences.

Preheating Technology: Instant Hot Water Delivery

Some high-end tankless water heaters, particularly certain gas models, incorporate preheating technology.

This feature maintains a small amount of heated water within the unit, ensuring that hot water is delivered almost instantaneously when a tap is opened.

This eliminates the brief wait time typically associated with tankless water heaters, where cold water initially flows through the pipes before the heated water arrives.

Preheating technology enhances user convenience but can slightly increase energy consumption, as the unit expends energy to maintain the preheated water.

It is often a user-selectable option, allowing individuals to prioritize instant hot water delivery or energy efficiency based on their preferences.

Performance Comparison: Flow Rate, Temperature Rise, and Efficiency

The practical performance of tankless water heaters hinges on several key metrics. These include flow rate, temperature rise, energy efficiency, and overall lifespan. Examining these factors allows for a more informed comparison between electric and gas models, revealing their respective strengths and weaknesses in real-world applications.

Flow Rate (GPM): Meeting Hot Water Demand

Flow rate, measured in gallons per minute (GPM), indicates the volume of hot water a tankless heater can deliver at a given time. This is a critical factor in determining whether a unit can simultaneously supply multiple hot water fixtures (showers, sinks, dishwashers) without a noticeable drop in temperature or pressure.

Gas tankless heaters generally offer higher flow rates compared to electric models. High-output gas units can often handle multiple simultaneous uses, making them suitable for larger households or applications with high hot water demand.

Electric tankless heaters, on the other hand, tend to have lower maximum flow rates. Selecting a unit with an inadequate flow rate can result in reduced hot water availability or a drop in temperature when multiple fixtures are used simultaneously.

Properly sizing a tankless water heater based on household demand is crucial to avoid these issues. Consult the GPM ratings to make the correct choice.

Temperature Rise: Achieving Desired Hotness

Temperature rise refers to the number of degrees Fahrenheit (or Celsius) that a tankless water heater can increase the temperature of the incoming water. This is especially important in regions with colder groundwater temperatures.

A higher temperature rise capability ensures that the unit can deliver adequately hot water, even when the incoming water is very cold.

Both electric and gas tankless heaters have limits to their temperature rise capabilities. The capacity to generate heat is directly proportional to the water flow, and vice-versa. Higher flow reduces heat capacity. Cooler incoming water requires a higher temperature rise to achieve a target temperature.

Gas tankless heaters typically offer a greater temperature rise range than electric models. This makes them better suited for colder climates where larger temperature differences are needed.

Electric tankless heaters can struggle to deliver a sufficient temperature rise in colder climates, particularly at higher flow rates. This limitation should be carefully considered when assessing the viability of an electric model.

Energy Efficiency: Minimizing Energy Waste

Energy efficiency is a crucial consideration for any water heater, impacting both operating costs and environmental footprint. Tankless water heaters are generally more energy-efficient than traditional tank heaters, as they only heat water on demand, eliminating standby heat loss.

Energy efficiency is usually expressed as an Energy Factor (EF). A higher EF rating indicates greater energy efficiency. However, real-world efficiency can vary depending on usage patterns and other factors.

Both electric and gas tankless heaters can achieve high levels of energy efficiency, but the specific values depend on the model and technology used. Modulating technology, as discussed earlier, plays a significant role in maximizing energy efficiency.

Gas tankless water heaters have evolved to match and sometimes exceed the efficiency of electric tankless, so there isn't necessarily a clear winner here.

The choice of fuel source (electricity vs. gas) also impacts the overall cost of operation, which will depend on local energy prices. This will be discussed in the operating costs section.

Life Expectancy: Long-Term Reliability

The life expectancy of a tankless water heater represents its expected lifespan under normal operating conditions. A longer lifespan translates to greater value and reduced replacement costs over time.

Gas tankless water heaters generally have a slightly longer lifespan than electric models. With proper maintenance, a gas tankless unit can last for 20 years or more. Electric tankless heaters typically have a lifespan of 10 to 15 years.

Factors such as water quality, usage patterns, and maintenance practices can significantly impact the lifespan of any water heater.

Regular descaling and adherence to manufacturer recommendations are essential for prolonging the life of both electric and gas tankless models.

Demand Hot Water: Meeting Expectations

Both electric and gas tankless water heaters are designed to provide on-demand hot water. This means that hot water is only produced when a tap is opened, eliminating the need to store a large volume of heated water in a tank.

While both types offer on-demand hot water, there are subtle differences in how quickly they can deliver it. Gas tankless heaters typically have a slightly faster response time, particularly for high-demand applications.

Electric tankless heaters may exhibit a brief delay before hot water is delivered, especially in colder climates or when the unit is initially activated.

Preheating technology, as mentioned earlier, can mitigate this delay in certain high-end gas models, providing near-instantaneous hot water delivery.

Installation and Operating Costs: A Financial Perspective

The financial implications of choosing between electric and gas tankless water heaters extend beyond the initial purchase price. Installation expenses and ongoing operating costs represent significant factors in the long-term affordability and value proposition of each system.

Installation Costs: Upfront Investment

The installation cost of a tankless water heater can vary significantly, influenced by factors such as the type of unit (electric or gas), the existing infrastructure, and local labor rates. Understanding these variables is crucial for accurate budgeting.

Electric tankless water heater installation often appears less complex at first glance, potentially leading to the misconception of lower upfront costs. However, electrical requirements, particularly amperage, can significantly increase installation expenses. Many electric models demand substantial electrical upgrades, including thicker gauge wiring and potentially a service panel upgrade to accommodate the increased load.

These upgrades, performed by a qualified electrician, can add hundreds or even thousands of dollars to the initial installation cost. The existing electrical capacity of a home is a critical determinant of the overall installation expense for electric tankless systems.

Gas tankless water heater installation, on the other hand, typically involves more complex plumbing and venting considerations.

Gas line installation or modification is frequently necessary, particularly in homes not already equipped with adequate gas infrastructure near the desired location. This can involve running new gas lines, upgrading existing lines to a larger diameter, and ensuring compliance with local gas codes.

Furthermore, gas units require a dedicated venting system to safely exhaust combustion byproducts, such as carbon monoxide, to the outside. Venting can be a significant expense, especially in older homes where existing chimneys may not be suitable or compliant with current safety standards.

Depending on the complexity of the venting requirements, this may involve professional chimney relining or the installation of a new direct-vent system. Proper permitting and inspections are also mandatory for gas appliance installations, adding to the overall cost.

Both electric and gas tankless water heater installations often necessitate the expertise of licensed plumbers and electricians. Their hourly rates and the complexity of the job will influence the final installation cost.

Obtaining multiple quotes from qualified professionals is highly recommended to ensure competitive pricing and a thorough assessment of the specific installation requirements.

Operating Costs: Ongoing Expenses

Operating costs represent the ongoing expenses associated with heating water, primarily influenced by energy consumption and local utility rates. A comprehensive cost comparison requires careful consideration of both electricity and gas prices in your region.

Electric tankless water heaters consume electricity directly to heat water. The operating cost is directly tied to the local cost per kilowatt-hour (kWh). While tankless models eliminate standby heat loss, the electricity consumption during operation can be substantial, especially during periods of high hot water demand.

In regions with high electricity prices, the operating costs of electric tankless heaters can be significantly higher compared to gas models. Consider off-peak electricity pricing programs offered by some utility companies, which could potentially lower the overall expense if hot water usage can be shifted to these times.

Gas tankless water heaters utilize natural gas or propane to heat water. The operating cost is determined by the local cost per therm (natural gas) or gallon (propane). In many areas, natural gas is a more cost-effective energy source compared to electricity, resulting in lower operating costs for gas tankless systems.

However, propane can be more expensive than natural gas in certain regions, potentially increasing the operating expenses of propane-powered tankless heaters. Fuel source availability (natural gas vs. propane) is another important consideration.

Regular maintenance, such as descaling to remove mineral buildup, can also impact operating costs. Scale buildup reduces the efficiency of both electric and gas models, requiring more energy to heat water. Adhering to the manufacturer's recommended maintenance schedule is crucial for optimizing energy efficiency and minimizing operating expenses.

Regulatory Compliance and Safety: Meeting Standards

The installation and operation of tankless water heaters, whether electric or gas-powered, are subject to stringent regulatory oversight designed to ensure safety and efficiency. Adherence to these standards is not merely a formality but a critical responsibility for homeowners and installers alike, protecting both property and well-being.

The Importance of Code Compliance

Building, plumbing, and electrical codes are the cornerstones of safe and compliant installations. These codes dictate specific requirements for materials, installation techniques, and safety features, reflecting the latest knowledge and best practices in the industry.

Ignoring these codes can lead to hazardous situations, including gas leaks, electrical fires, carbon monoxide poisoning, and improper venting, all of which pose significant risks to occupants.

Compliance with local codes is also often a prerequisite for insurance coverage and property resale. Non-compliant installations may invalidate warranties and create legal liabilities.

Understanding Building Codes

Building codes establish general safety requirements for structures, including provisions for fire protection, structural integrity, and proper ventilation. Tankless water heater installations must comply with these broader building regulations.

Navigating Plumbing Codes

Plumbing codes address the safe and efficient distribution of potable water and the proper disposal of wastewater. These codes specify requirements for pipe materials, fittings, connections, and backflow prevention devices to protect the water supply from contamination.

Gas tankless water heaters also require adherence to specific plumbing codes related to gas line installation, pressure testing, and leak detection.

Adhering to Electrical Codes

Electrical codes govern the safe installation and operation of electrical systems, including wiring, grounding, and overcurrent protection. Electric tankless water heaters, in particular, demand strict adherence to electrical codes due to their high amperage requirements.

Proper wiring gauge, circuit breaker sizing, and grounding are crucial to prevent electrical fires and ensure safe operation.

Energy Efficiency Standards and Certifications

Beyond safety, regulatory compliance also encompasses energy efficiency standards aimed at reducing energy consumption and promoting sustainable practices. ENERGY STAR certification is a widely recognized indicator of energy efficiency.

ENERGY STAR-certified tankless water heaters meet specific performance criteria established by the Environmental Protection Agency (EPA), ensuring that they operate efficiently and minimize energy waste.

Local Regulations and Permits

In addition to national standards, local jurisdictions may have their own specific regulations and permitting requirements for tankless water heater installations. It is essential to consult with local building officials to determine the applicable requirements in your area.

Permitting processes typically involve submitting plans, undergoing inspections, and paying fees. While seemingly burdensome, these processes ensure that installations meet all applicable codes and regulations, providing peace of mind and protecting your investment.

Popular Brands and Manufacturers: A Market Overview

The tankless water heater market boasts a diverse landscape of manufacturers, each offering a range of models with varying features, performance capabilities, and price points. Navigating this landscape can be daunting for consumers.

This section provides a brief overview of some of the more notable brands, serving as a starting point for further research and comparison. This information should aid in identifying manufacturers whose products align with specific needs and priorities.

Rheem

Rheem is a well-established name in the water heating industry, offering both electric and gas tankless models. They are generally known for their reliability and wide availability.

Rheem’s offerings cater to a broad spectrum of needs, from compact, point-of-use electric units to high-capacity gas models suitable for larger households. Their product line incorporates features like digital thermostats and self-diagnostic systems.

Rinnai

Rinnai is a Japanese manufacturer renowned for its focus on gas-powered tankless water heaters. They are often considered a premium brand, emphasizing quality and technological innovation.

Rinnai units often feature sophisticated controls, multi-point systems, and advanced safety features. Their products are generally positioned towards homeowners seeking high performance and long-term reliability.

Navien

Navien, another prominent player in the tankless market, distinguishes itself with its condensing technology. This technology allows for higher energy efficiency compared to non-condensing models.

Navien offers both gas tankless water heaters and combi-boilers. The combi-boilers provide space heating and domestic hot water, suitable for a whole house.

Navien places a strong emphasis on eco-friendly operation.

EcoSmart

EcoSmart specializes primarily in electric tankless water heaters, focusing on energy efficiency and ease of installation. Their models are often compact and designed for point-of-use or supplemental heating applications.

EcoSmart aims to provide cost-effective solutions for homeowners looking to reduce energy consumption and save space. They are noted for ease of install.

Stiebel Eltron

Stiebel Eltron is a German manufacturer known for its high-quality electric tankless water heaters. The company has earned a reputation for durability and precise temperature control.

Their products are often favored in applications where precise temperature regulation is critical, such as laboratories or specific industrial processes. The units are also well-suited for residential use.

Takagi

Takagi offers a range of gas tankless water heaters. These are designed for both residential and commercial applications.

Takagi models are often praised for their robust performance and reliability, even under demanding conditions. Their focus is on providing dependable hot water solutions for a variety of settings.

It's important to note that this is not an exhaustive list, and other reputable manufacturers exist in the market. Furthermore, product lines and specifications can change rapidly. Consumers are encouraged to conduct thorough research and consult with qualified professionals. This ensures selecting a tankless water heater that best meets their individual needs and circumstances.

Key Concepts and Measurements: Understanding the Terminology

Throughout this comparison of electric and gas tankless water heaters, we've referenced several key concepts and measurements. Ensuring a clear understanding of these terms is crucial for making an informed decision. This section provides concise definitions and explanations to solidify your comprehension.

Understanding Flow Rate (GPM)

Flow rate, measured in gallons per minute (GPM), indicates the volume of hot water a tankless heater can deliver at a given time. A higher GPM rating is necessary to simultaneously run multiple hot water fixtures, like showers and faucets.

Selecting a unit with an insufficient GPM rating can lead to a frustrating experience. The user may experience a drop in water pressure or temperature fluctuations when multiple outlets are in use.

Demystifying Temperature Rise

Temperature rise refers to the increase in water temperature that a tankless water heater can achieve. It's the difference between the incoming cold water temperature and the desired output temperature.

For example, if your incoming water is 60°F and you want to shower at 105°F, you need a temperature rise of 45°F. Tankless heaters are often specified by their GPM at a certain temperature rise.

Energy Efficiency Explained

Energy efficiency, often expressed as an Energy Factor (EF) or Uniform Energy Factor (UEF), represents how efficiently a water heater converts energy into hot water. A higher EF/UEF indicates greater energy efficiency and lower operating costs.

Tankless water heaters generally boast higher energy efficiency compared to traditional tank heaters. This is due to the elimination of standby heat loss.

Assessing Life Expectancy

Life expectancy refers to the estimated lifespan of a water heater. Gas tankless models typically last longer (20+ years) than electric models (10+ years) due to the lower stress on components.

However, factors like water quality, usage patterns, and maintenance practices can significantly impact the actual lifespan of any water heater.

Delving into Installation Costs

Installation costs encompass all expenses associated with setting up the tankless water heater. This includes plumbing, electrical work, venting (for gas models), and labor charges.

Gas tankless installations often involve higher upfront costs due to the need for gas line connections and venting systems. Electric models may require significant electrical upgrades, adding to the initial expense.

Understanding Operating Costs

Operating costs refer to the ongoing expenses of using the tankless water heater. The single highest operating cost is most often the fuel source itself.

This is primarily electricity for electric models and natural gas or propane for gas models. These costs are directly tied to local energy prices and usage habits.

Defining Demand Hot Water

"Demand hot water" is a key feature of tankless systems. The tankless system instantaneously heats water as it flows through the unit, providing a continuous supply of hot water on demand.

The user is only paying to heat water when needed, unlike traditional tank heaters. The tank heater cycles on and off to maintain temperature.

Hard Water Considerations

Hard water contains high levels of minerals like calcium and magnesium. Over time, these minerals can accumulate inside the heat exchanger, reducing efficiency and potentially causing damage.

Scale prevention technology or the use of a water softener can mitigate the negative effects of hard water and extend the lifespan of your tankless unit.

Okay, so there you have it! Choosing between an electric tankless water heater vs gas really boils down to your home's specific needs and budget. Hopefully, this has given you some food for thought as you weigh your options and make the best decision for your hot water future. Happy showering!