Tankless water heaters have become famous for homeowners seeking energy-efficient solutions that provide on-demand hot water. Unlike traditional storage tank heaters, which continuously heat and store water, tankless systems heat water only when needed, saving energy and space. With advancements in technology, these heaters are now more efficient, reliable, and capable of serving households of various sizes. However, choosing the right tankless water heater involves considering factors such as flow rate, energy source, and installation costs. This guide explores the best tankless water heaters available today, helping you find the ideal model for your home.
Key Takeaways:
- Energy Efficiency: Tankless water heaters significantly reduce energy consumption by only heating water when necessary, unlike traditional heaters that continuously heat stored water. This reduces utility bills and environmental impact over time.
- Flow Rate is Crucial: The flow rate (gallons per minute, or GPM) is critical in choosing a tankless water heater. A higher flow rate is required for larger households or homes with several water fixtures operating simultaneously to prevent problems such as temperature dips.
- Installation Costs and Considerations: Even while tankless water heaters save money over time, installation can be expensive up front, particularly for gas-powered models. Professional installation is often advised to guarantee safety and optimal operation, especially for gas models that need venting.
What is a Tankless Water Heater?
An instantaneous or on-demand water heater, also known as a tankless water heater, warms water only when needed. Unlike conventional tank water heaters, which hold hot water in a large tank, tankless water heaters use electric solid or gas burners to heat water as it passes through the device. This eliminates the need for a storage tank and guarantees a constant hot water supply.
How Tankless Water Heaters Work (On-Demand Hot Water Production)
When you turn on a hot water tap, cold water travels through the tankless heater. The water is heated rapidly by an electric element or gas burner. Therefore, you won’t have to wait for a storage tank to fill to benefit from a continuous hot water supply. The system is designed to provide only hot water when needed, so there’s no standby energy loss, a common problem with traditional tank water heaters.
Tankless and Traditional Tank Water Heaters Differences
- Storage: Traditional water heaters store a certain amount of hot water (typically 40 to 80 gallons), while tankless systems heat water on demand and do not store it.
- Energy Usage: Traditional heaters continually heat stored water, wasting energy over time (standby heat loss). Tankless versions are more energy-efficient since they only draw power when hot water is needed.
- Flow Rate: Tankless heaters are limited by their flow rate, meaning that if multiple hot water outlets are in use, performance could be reduced, while traditional heaters can deliver hot water until the tank runs out.
Tankless Water Heaters Advantages
- Energy Efficiency: Tankless water heaters minimize standby energy loss by heating water only when needed, making them energy-efficient. This efficiency can reduce utility bills, especially in homes with lower hot water demand.
- Space-saving: Tankless water heaters are compact and do not require a large storage tank installed in small spaces.
- Continuous Hot Water Supply: Unlike traditional tank heaters that can run out of hot water once the tank is depleted, tankless systems provide a constant hot water supply as long as the unit’s flow rate isn’t exceeded.
Tankless Water Heaters Disadvantages
- Higher Costs: Tankless water heaters are more expensive than conventional tank systems, particularly for gas-powered versions requiring special venting.
- Flow Rate Limitations: The amount of hot water a tankless heater can provide is limited by its flow rate. Showers, dishwashers, and faucets are fixtures that might struggle to produce enough hot water simultaneously, causing temperature fluctuations in the heater.
Tankless Water Heater Key Features
Flow Rate (GPM – Gallons per Minute)
The highest amount of hot water a tankless heater can generate at any given moment is its flow rate, defined as gallons per minute (GPM). The flow rate is crucial because it regulates the amount of hot water the unit can generate while many fixtures operate simultaneously. For example, a shower might require 2.5 GPM, while a dishwasher may need 1.5 GPM.
How to Calculate the Flow Rate Needed Based on Household Size
To choose the right tankless water heater, you need to estimate your household’s hot water demand by adding up the GPM requirements for all the appliances and fixtures that might be used simultaneously.
| Fixture/Appliance | Average Flow Rate (GPM) |
| Shower | 2.0 – 2.5 |
| Dishwasher | 1.5 – 2.0 |
| Kitchen Faucet | 1.5 – 2.2 |
| Washing Machine | 2.0 – 2.5 |
For example, if you plan to run a shower (2.5 GPM), kitchen faucet (1.5 GPM), and washing machine (2.5 GPM) at the same time, your tankless water heater should be able to handle a minimum flow rate of 6.5 GPM.
Energy Efficiency (EF – Energy Factor Rating)
Due to their ability to heat water only when necessary and to prevent standby heat loss, tankless water heaters utilize less energy than traditional ones. As a result, utility expenditures can be significantly reduced, particularly in houses with modest hot water usage.
Explanation of EF and How It Impacts Long-Term Costs
Energy Factor (EF) measures the efficiency of water heaters. The higher the EF, the more energy-efficient the unit. Tankless water heaters typically have EF ratings of 0.8 to 0.99, which means they convert 80% to 99% of the energy they consume into hot water.
| Type of Heater | Average EF Rating | Energy Efficiency |
| Traditional Tank | 0.55 – 0.65 | Moderate |
| Tankless Electric | 0.9 – 0.99 | High |
| Tankless Gas | 0.82 – 0.94 | High |
Higher EF ratings translate to lower operating costs over time, so selecting a tankless water heater with a higher EF can lead to more significant long-term savings.
Fuel Type: Electric vs. Gas
| Type | Pros | Cons |
| Electric |
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| Gas |
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Installation Costs and Requirements for Each Type
- Electric heaters are typically more accessible and cheaper to install since they don’t require venting. They work well in smaller homes or for individual fixtures.
- Gas heaters require professional installation because they need venting to remove exhaust gases safely. While installation costs are higher, gas heaters are generally better for larger households due to their higher flow rates.
Sizing & Placement
Compact Design Advantages
The small size of tankless water heaters is one of their main advantages. Tankless water heaters are the best option for households with limited storage space since they don’t require as much room as standard water heaters because they need a storage tank. Important floor areas may be freed up by mounting tankless units on walls.
Placement Considerations: Indoor vs. Outdoor Units
- Indoor Units: More common in colder climates, indoor tankless water heaters are installed inside to protect them from freezing temperatures. If they are gas-powered, they require venting.
- Outdoor Units: Outdoor units can reduce interior space and venting requirements in warmer regions. However, they can need freeze protection in some places.
| Consideration | Indoor Unit | Outdoor Unit |
| Space | It takes up minimal indoor space | Saves indoor space, requires no venting |
| Weather | Protected from outdoor elements | Requires freeze protection in cold areas |
| Installation Cost | Requires venting for gas models | It is a less expensive installation without venting |
Top 5 Best Tankless Water Heaters in 2024
When it comes to selecting the best tankless water heaters, the options in 2024 are more efficient and feature-rich than ever before. Whether you’re looking for a powerful gas unit, an easy-to-install electric option, or a budget-friendly choice, here are the top 5 models, each excelling in different areas.
Rinnai RUR199iN (Best for Natural Gas)
- Features: Recirculation technology, high flow rate (up to 11 GPM), and WiFi remote control and monitoring capabilities.
- Pros: It is highly energy-efficient and has a built-in recirculation pump that reduces water waste and speeds up hot water delivery. The WiFi connectivity allows for advanced control and diagnostics.
- Cons: Installation is expensive due to venting and gas line requirements. It’s a premium unit, so the upfront cost is high.
Stiebel Eltron Tempra Plus 24 kW (Best for Electric)
- Features: Advanced flow control, energy-saving features, and compact design.
- Pros: Electric models like the Stiebel Eltron Tempra Plus don’t require venting, making installation simpler. The unit adjusts its power output based on the hot water demand, ensuring optimal energy savings.
- Cons: The limited flow rate is suitable only for smaller households with fewer hot water demands.
EcoSmart ECO 27 (Best Budget Option)
- Features: Self-modulating technology that adjusts energy consumption based on water usage.
- Pros: This affordable and highly energy-efficient model is a great budget option. It’s compact and designed for easy installation in small spaces.
- Cons: While cost-effective, it requires professional installation to handle high flow demands, especially in colder climates.
Rheem RTEX-18 (Best for Small Homes)
- Features: Advanced temperature control and easy installation.
- Pros: Reliable and simple to maintain, the Rheem RTEX-18 is ideal for small households. It is compact and features user-friendly controls for adjusting water temperature.
- Cons: This model is limited to small or medium-sized homes and may need to provide adequate hot water for larger families or homes with higher water demand.
Noritz NRC66DV (Best for Outdoor Use)
- Features: Designed for outdoor installation, it’s compact and highly energy-efficient, suitable for homes in warmer climates.
- Pros: Saves indoor space and eliminates the need for venting since it is installed outside. It’s a good option for homes with limited indoor space.
- Cons: Requires protection from extreme weather conditions, particularly in colder climates, which may add to the installation cost.
Comparison Table of Top 5 Tankless Water Heaters
| Model | Fuel Type | Flow Rate (GPM) | Best For | Key Features | Pros | Cons |
| Rinnai RUR199iN | Natural Gas | 11 GPM | High-demand homes | Recirculation technology, WiFi | Energy-efficient, reliable, fast hot water | Expensive installation requires a professional setup |
| Stiebel Eltron Tempra Plus 24 kW | Electric | 4.5 GPM | Small households | Advanced flow control, no venting needed | No venting, energy-saving, easy to install | Limited to smaller households |
| EcoSmart ECO 27 | Electric | 6.5 GPM | Budget-conscious buyers | Self-modulating technology | Affordable, energy-efficient, compact | Professional installation is needed for high-flow |
| Rheem RTEX-18 | Electric | 4.4 GPM | Small homes | Easy temperature control | Reliable, simple maintenance, easy installation | Limited to small to medium-sized homes |
| Noritz NRC66DV | Natural Gas | 6.6 GPM | Outdoor installations | Designed for outdoor use, energy-saving | Saves space, no indoor venting | Requires weather protection in colder climates |
Pros and Cons of Tankless Water Heaters
Pros:
- Energy-Efficient (No Standby Heat Loss): Energy efficiency is one of the advantages of tankless water heaters. Conventional tank heaters lose standby heat because they continuously heat water while it’s not in use. By heating water only when necessary, tankless heaters solve this problem and can drastically save energy use and utility costs.
- Unlimited Hot Water Supply: When the tank is empty, the amount of hot water that tankless water heaters may heat is infinite, but that of tank water heaters is restricted. Therefore, they are perfect for households with high hot water demand or where several people want hot water simultaneously.
- Longer Lifespan: Tankless water heaters last longer than traditional models. While conventional tank water heaters last about 8 to 12 years, tankless units can last 15 to 20 years with proper maintenance. This longer lifespan adds to the overall value of a tankless system.
- Space-Saving Design: Without a bulky tank to store water, tankless units are compact and can be mounted on walls, saving valuable floor space. This makes them an excellent option for homes with limited storage or utility space.
Cons:
- Higher Cost: The initial cost of buying and installing a tankless water heater is much greater than a conventional tank heater. The kind (gas or electric), size, and particular installation requirements can all affect the cost. Some homeowners may find this larger upfront cost prohibitive despite the long-term savings.
- Limited Flow Rate Can Affect Large Households: Despite offering an endless hot water supply, tankless water heaters have a limited flow rate. If multiple fixtures (such as showers, dishwashers, and washing machines) are used simultaneously, the tankless unit may need help to keep up, resulting in consistent water temperatures. This can be a drawback for large households with high hot water demands.
- Complex Installation Process: Tankless water heater installation can be trickier than typical tank installation, particularly for gas systems that must be adequately vented. Electric models may also require electrical upgrades to handle the increased power load. Professional installation is typically necessary, adding to the overall cost.
- Requires Regular Maintenance for Descaling: Tankless water heaters, especially in areas with hard water, require regular maintenance to prevent limescale buildup inside the unit. Over time, mineral deposits can reduce efficiency and lead to costly repairs. Descaling the system periodically is necessary to keep it running efficiently, which requires effort or professional servicing.
Maintenance and Lifespan of Tankless Water Heaters
Routine Maintenance to Prevent Limescale Buildup
Limescale accumulation can occur with tankless water heaters, especially in challenging water locations. The heating components of the unit may eventually become clogged with minerals such as calcium and magnesium, which limit the device’s lifespan and reduce its efficiency. Routine maintenance, including regularly descaling or flushing the system to remove mineral deposits, is essential to prevent this.
Typical Lifespan (15-20 Years with Proper Maintenance)
One of tankless water heaters’ most alluring features is their extended lifespan. These devices may survive 15 to 20 years with adequate care and maintenance, considerably longer than standard tank warmers. The extended lifespan makes tankless systems a more cost-effective investment in the long run, provided that regular maintenance is performed.
Descaling and Flushing Procedures
To ensure efficient operation, tankless water heaters must be descaled or flushed at least once a year, especially in challenging water areas. This involves running a solution, typically vinegar or a descaling product, through the system to dissolve mineral deposits. Some manufacturers also offer cleaning kits for easier maintenance. Neglecting this step can lead to inefficiencies, reduced water flow, and higher energy consumption.
Importance of Professional Servicing
While some homeowners may be comfortable performing basic maintenance tasks, such as flushing the system, it is advisable to have a professional inspect the unit annually. A skilled technician can check for any signs of wear and tear, ensure all components function correctly, and perform more in-depth maintenance tasks as needed. This helps to extend the unit’s lifespan and prevent costly repairs down the line.
Cost Considerations
Upfront Costs
The initial cost of ownership for a tankless water heater differs based on the model’s features, capacity, and type (gas or electric). Additionally, the installation fees for gas units are generally higher due to the need for proper venting and gas line work.
Price Comparison Between Gas and Electric Tankless Heaters
| Type | Average Unit Cost | Installation Cost | Total Estimated Upfront Cost |
| Electric | $500 – $1,200 | $300 – $1,000 | $800 – $2,200 |
| Gas | $1,000 – $2,000 | $1,000 – $3,000 (venting required) | $2,000 – $5,000 |
- Electric Tankless Heaters: These models generally have lower upfront unit costs and more straightforward installation procedures. However, the final price depends on the need for electrical upgrades in the home.
- Gas Tankless Heaters: While more expensive to purchase and install, gas units perform better, especially in larger households. They also require additional venting systems, which increases the installation cost.
Installation Fees and Additional Costs
- Venting for Gas Units: Gas tankless heaters require a proper venting system to expel combustion gases, which increases the installation cost. In some cases, new venting systems must be installed, adding up to $1,500 or more.
- Electrical Upgrades: For electric tankless heaters, homes may require electrical panel upgrades or additional wiring to handle the increased energy load, which can add several hundred dollars to the installation.
Long-Term Savings
While the upfront costs for tankless water heaters are higher than traditional tank models, the long-term savings can offset this initial investment over time. The key to these savings lies in the energy efficiency of tankless heaters, which only heat water when needed, as opposed to continuously heating stored water.
Energy Savings During the Unit’s Life
Compared to standard tank types, tankless water heaters are generally 24–34% more energy-efficient for residences that use 41 gallons or less of hot water weekly. Larger households using around 86 gallons daily can still see a 10-15% improvement in energy efficiency. Throughout the unit’s 15–20-year lifespan, this leads to cheaper energy expenses.
| Type | Annual Energy Savings | Lifespan (Years) | Total Energy Savings |
| Electric | $100 – $200 | 15 – 20 | $1,500 – $4,000 |
| Gas | $150 – $300 | 15 – 20 | $2,250 – $6,000 |
- Lower Operational Costs: Tankless water heaters have lower operational costs than traditional water heaters. Depending on usage, energy rates, and the unit type, the energy savings over the unit’s lifespan can range from $1,500 to $6,000.
FAQs
Do tankless water heaters work in cold climates?
While they may not operate as well in icy areas, tankless water heaters can still function. Select a model that effectively manages cooler water temperatures and has a higher flow rate.
How long do tankless water heaters last?
Tankless water heaters may last up to 20 years with regular maintenance, much longer than standard ones.
Can I do my tankless water heater installation?
While it’s possible to install an electric tankless water heater yourself if you have plumbing experience, gas tankless heaters should permanently be installed by a professional due to the need for proper venting and gas connections.
Are tankless water heaters noisy?
Some tankless water heaters can produce noise when heating water, but many modern models are designed to operate quietly. Noise is typically more noticeable in gas models due to combustion.
How much energy can I save with a tankless water heater?
Tankless water heaters can save 24–34% of the energy traditional water heaters use in homes with 41 gallons or less daily. Larger households using more hot water may still see a 10-15% improvement in energy efficiency.
Conclusion
Modern, cost-effective tankless water heaters are an excellent choice for homes trying to reduce energy expenses while ensuring a steady hot water supply. Despite the higher upfront costs, these systems provide significant long-term savings due to their ability to heat water on demand, eliminating standby energy loss. Their space-saving design and longer lifespan add to their appeal, especially in homes with limited space.
However, it’s essential to consider factors such as flow rate limitations, which can affect larger households, and the more complex installation process, particularly for gas models that require venting. Regular maintenance, such as descaling, ensures optimal performance, especially in challenging water areas.
Ultimately, tankless water heaters represent an investment that, over time, can offer both financial and environmental benefits. You can maximize the benefits of this efficient technology by choosing the suitable model for your home’s hot water demands and fuel availability.