Finding the best electric tankless water heater for whole house use involves balancing capacity, energy efficiency, and installation complexity. The Rheem RTEX-24 stands out for its reliable performance and straightforward setup, making it a top choice for many homes. For those seeking higher flow rates, the Mizudo 36kW offers impressive hot water output but requires a larger electrical setup. Meanwhile, models like the WINTEMP 18kW incorporate smart features such as WiFi control, appealing to tech-savvy buyers. The main tradeoffs in this category include capacity limits versus installation demands and upfront costs versus long-term savings. Continue reading for an in-depth comparison tailored to different home needs and budgets.
Key Takeaways
- High wattage models like Mizudo 36kW provide greater flow rates but demand more electrical capacity and space for installation.
- Self-modulating units such as the SIVUATEK series help optimize energy use, reducing operational costs over time.
- Features like WiFi control and digital displays add convenience but often come with a higher price point.
- Size and installation complexity vary widely; compact models suit smaller homes or point-of-use setups, while larger units serve entire households.
- Price ranges reflect capacity and feature sets; investing more typically ensures better longevity and performance.
More Details on Our Top Picks
Rheem RTEX-24 24kW 240V Electric Tankless Water Heater, Gray
This Rheem model stands out for its proven ability to supply continuous hot water across larger homes, especially when compared to smaller units like the WINTEMP 18kW. It delivers a flow rate of 5.9 GPM, making it suitable for multiple fixtures simultaneously, but it requires a robust electrical system, including three 40 AMP double-pole breakers, which might challenge smaller or older homes. Its digital temperature control offers precise adjustments, though the installation complexity and electrical demands could be a hurdle for DIYers. Compared to the APUS 27kW, this Rheem unit is more powerful and reliable for whole-house needs, but it also consumes more energy and needs a spacious breaker panel. Its space-saving design and efficiency are pluses, yet the need for significant electrical upgrades limits its suitability for some residences. Overall, this model makes the most sense for homeowners with ample electrical capacity seeking a dependable, high-capacity heater.
Pros:- High flow rate of 5.9 GPM supports multiple fixtures at once
- Precise digital temperature control in 1-degree increments
- Compact, space-saving design
Cons:- Requires three 40 AMP double-pole breakers and significant electrical upgrades
- Installation complexity may necessitate professional wiring
- Higher energy consumption due to its power size
Best for: Homes with existing high-capacity electrical panels and those needing reliable, whole-house hot water.
Not ideal for: Older homes with limited electrical service or those unwilling to upgrade their panel and wiring.
- Wattage:24 KW
- Voltage:240 V
- Flow Rate:5.9 GPM
- Maximum Temperature:140°F
- Mount Type:Wall
- Efficiency:99.8%
Bottom line: Best suited for large households with robust electrical systems that need dependable whole-house hot water.
27kW Tankless Water Heater Electric, APUS 240V On Demand Instant Hot Water with Memory Function & LED Display
This APUS 27kW heater offers impressive flow capacity of up to 6.5 GPM, making it a strong contender for mid-sized homes, especially when compared to the smaller WINTEMP 18kW. It features a smart control system with memory functions and precise temperature adjustments (86°F-140°F), ensuring comfort and energy efficiency, while its self-modulating technology reduces power waste. Its sleek, compact design (17.72″ x 11.42″) simplifies installation, especially in tight spaces, but the requirement of three 40 AMP breakers and 6 AWG wiring could be a barrier for some DIYers. Unlike the Rheem RTEX-24, which offers higher power, this model balances capacity with ease of installation and lower power demands. Its robust safety protections and high efficiency make it a good choice for those wanting reliable performance without overhauling their electrical system.
Pros:- Supports up to 6.5 GPM, suitable for 3-4 fixtures simultaneously
- Smart, self-modulating tech for energy savings
- Compact design facilitates installation in small spaces
Cons:- Requires three 40 AMP breakers and 6 AWG wiring, which might be difficult for some homes
- Less power than the Rheem RTEX-24, limiting maximum flow in very large households
- Potentially higher initial cost due to advanced features
Best for: Households with moderate hot water needs, seeking a balance of capacity, efficiency, and easier wiring requirements.
Not ideal for: Homes with extremely high flow demands or limited electrical capacity that cannot support 3×40A breakers.
- Wattage:27,000 watts
- Voltage:240 V
- Flow Rate:Up to 6.5 GPM
- Maximum Temperature:140°F
- Mount Type:Wall
- Efficiency:99.8%
Bottom line: Ideal for medium-sized homes looking for efficient, space-saving hot water with manageable electrical requirements.
Electric Tankless Water Heater SIVUATEK 14kW, 240V
This SIVUATEK 14kW heater excels for point-of-use situations, such as a bathroom or laundry area, especially when compared to larger whole-house models like the Rheem RTEX-24. It provides a steady output of hot water at 2.3 GPM, ideal for smaller fixtures or localized heating needs, but it’s not designed to supply entire homes. Its simple digital display and touch controls are user-friendly, though its lower wattage limits flow rate and overall capacity, making it unsuitable for whole-house use. The unit’s compact size (12.2″ x 17.25″) and self-modulating technology support energy efficiency, but it requires a dedicated 240V circuit with a 40A breaker and proper wiring. It’s a reliable, safe choice for specific points of use rather than full home supply, contrasting with the higher-capacity Rheem or APUS units.
Pros:- Supports up to 2.3 GPM for point-of-use needs
- Simple digital controls with precise temperature adjustments
- Self-modulating for energy efficiency
Cons:- Limited to small flow rates, unsuitable for whole-house use
- Lower wattage means only one fixture at a time
- Not designed for high-demand applications
Best for: Homeowners needing reliable hot water at specific fixtures like sinks or washing machines, not large households with multiple simultaneous demands.
Not ideal for: Households requiring hot water throughout the entire house simultaneously or larger capacity applications.
- Wattage:14 KW
- Voltage:240 V
- Flow Rate:2.3 GPM
- Maximum Temperature:110°F
- Mount Type:Wall
- Efficiency:98%
Bottom line: Best suited for localized hot water needs where space and simplicity are priorities, not for whole-house systems.
18kW Tankless Water Heater Electric 240V WINTEMP
This WINTEMP 18kW heater is ideal for small-scale applications like a single bathroom sink or laundry, especially when compared to larger units like the Rheem RTEX-24. Its small size (11.1″ W x 19.1″ H, 12 pounds) makes it easy to install in tight spaces, but it has a maximum flow of only 4.3 GPM, limiting its use for whole-house needs. Its self-regulating technology and LED display facilitate safe, efficient operation, though it requires a dedicated 150A household service, which could be restrictive for some homes. Compared to the APUS 27kW, this unit is less powerful but more space-efficient. Its safety features and simple controls make it a strong choice for localized or point-of-use installations, rather than large capacity household systems.
Pros:- Very compact and lightweight for easy installation
- Self-modulating technology for energy efficiency
- ETL Certified for safety
Cons:- Limited flow rate of 4.3 GPM, not for whole house
- Requires a 150A service, which may not be available in older homes
- Lower capacity compared to larger units like Rheem or APUS
Best for: Single fixture or small point-of-use installations in homes or apartments with limited electrical capacity.
Not ideal for: Whole-house applications or households with multiple simultaneous hot water demands.
- Wattage:18 KW
- Voltage:240 V
- Flow Rate:4.3 GPM
- Maximum Temperature:140°F
- Mount Type:Wall
- Efficiency:98%
Bottom line: Excellent for small-scale or point-of-use applications in space-constrained homes, not for whole-house use.
SIVUATEK 18kW, 240V – On-Demand Hot Water for Whole House
This SIVUATEK 18kW heater provides a flow rate of 2.8 GPM, making it suitable for smaller households or homes with limited hot water demand, especially when compared to the Rheem RTEX-24. It features safety protections like leakage and overheat protection, along with ETL certification, ensuring safe operation. Its self-modulating system improves efficiency, but its flow rate limits its capacity to supply multiple fixtures simultaneously, which might be a drawback for larger families. The compact wall-mounted design (11″ W x 3″ H) simplifies installation, yet its lower power output compared to higher-capacity models restricts its use to moderate demands. Overall, a good choice for homes that want a reliable, space-efficient heater for partial or moderate whole-house use, but not for full simultaneous fixture support.
Pros:- Supports up to 2.8 GPM, suitable for small to medium households
- Self-modulating for energy efficiency
- ETL Certified with multiple safety protections
Cons:- Flow rate limits support for multiple fixtures at once
- Lower power compared to larger models like Rheem RTEX-24
- Flow rate of only 2.8 GPM restricts large household use
Best for: Moderate household demand where space and safety are priorities, but full simultaneous use isn’t necessary.
Not ideal for: Large households needing high flow rates or simultaneous fixture supply.
- Wattage:18 KW
- Voltage:240 V
- Flow Rate:2.8 GPM
- Maximum Temperature:125°F
- Mount Type:Wall
- Efficiency:99.8%
Bottom line: Well-suited for moderate household needs with space constraints, not for large, simultaneous demands.
18kW Tankless Water Heater Electric – ORBEK On Demand Instant Hot Water Heater 240V, Up to 4.17 GPM, Supply for 2-3 Fixtures, ETL Certified, Whole House Hot Water Supply, New Upgraded 2.0
This 18kW ORBEK model stands out for combining reliable performance with space-saving design, making it ideal for small to medium households needing hot water for 2-3 fixtures simultaneously. Compared with the Rheem RTEX-11, it offers a higher flow rate of 4.17 GPM, suitable for modest whole-house applications. However, its requirement for two 40A double-pole breakers and the need for significant wiring may pose installation challenges for DIY enthusiasts, unlike the Rheem RTEX-11, which is simpler to set up. Its advanced safety features and digital display allow precise temperature control, but the unit’s power needs and wiring complexity mean it’s best for those with electrical experience or professional help. This model is perfect for homeowners upgrading from tank systems who want an efficient, space-saving solution without extensive capacity.
Pros:- Compact size fits into tight spaces easily
- High efficiency with potential energy savings of up to 60%
- Advanced safety features including leakage and over-temperature protection
- Digital LED display for precise temperature control
Cons:- Requires significant electrical wiring and breaker upgrades
- Installation may be complex for non-professionals
Best for: Homeowners with small to medium household hot water needs, comfortable with electrical installations or willing to hire an electrician.
Not ideal for: People in larger homes with high simultaneous hot water demand or those lacking electrical capacity for high-power units.
- Power Source:240V AC
- Flow Rate:Up to 4.17 GPM
- Temperature Range:86°F to 140°F
- Safety Features:Leakage, over-temp, dry-heating protections
- Dimensions:17″H x 13″L x 3.9″W
- Certification:ETL
Bottom line: This unit suits those seeking a space-efficient, reliable whole-house heater with moderate flow capacity and electrical know-how.
Mizudo 36kW Tankless Water Heater Electric, 240 Volt Instant Hot Water Heater, Up to 8.7 GPM for the Whole House Shower, 5-6 Points of Use, with LED Digital Display, Copper Cup Heating Element
The Mizudo 36kW model makes a compelling case for very high-demand households, offering up to 8.7 GPM, which can comfortably supply 5-6 points of use simultaneously. Unlike the Rheem RTEX-24, which is slightly less powerful and more suited for mid-sized homes, this unit is designed for larger families or homes with multiple bathrooms running at once. Its high wattage requires four 40A breakers and substantial wiring, making professional installation essential—similar to the Rheem 18kW but on a larger scale. The LED display allows for accurate temperature adjustments, and its copper heating elements enhance durability. The tradeoff is that the installation complexity and electrical requirements are significant, and it might be overkill for smaller households. This heater is best for large homes or those with intensive hot water needs willing to invest in professional wiring.
Pros:- Very high flow rate suitable for large families
- Durable copper heating elements for longevity
- Smart temperature control with LED display
- Energy-efficient design reduces costs
Cons:- Requires four 40A breakers and extensive wiring
- Installation complexity may require professional help
Best for: Large households with high simultaneous hot water usage, equipped with sufficient electrical capacity and ready for complex installation.
Not ideal for: Small households or users looking for an easy-to-install, low-power unit that fits in limited spaces.
- Power Source:240V AC
- Flow Rate:Up to 8.7 GPM
- Wattage:36 kW
- Temperature Range:86°F to 140°F
- Heating Elements:Copper immersion
- Dimensions:17.1″H x 18.5″L x 3.7″W
Bottom line: Ideal for large homes needing maximum hot water flow and capacity, with the willingness to handle complex wiring and installation.
Rheem 11kW 240V Tankless Electric Water Heater
The Rheem RTEX-11 offers a compact, straightforward design, making it suitable for point-of-use applications or small homes with minimal hot water needs. Its self-modulating technology adjusts power efficiently, which can reduce energy costs, but its lower flow rate of 2.68 GPM limits its capacity for larger households. Compared to the Mizudo 36kW, this model is easier to install and requires less electrical infrastructure, fitting well under sinks or in small utility spaces. The digital temperature display and simple on/off control make it user-friendly, though it’s not intended for large-scale whole house use where multiple outlets demand hot water simultaneously. This heater works best for single fixtures or small apartments rather than entire homes with high flow requirements.
Pros:- Compact size fits into tight spaces
- Self-modulating power control saves energy
- Easy to operate with digital temperature display
- No venting required, simple installation
Cons:- Limited flow rate restricts use for whole house
- Not suitable for high-demand households
Best for: Individuals or small families needing reliable hot water for a single point or small area, with limited electrical capacity.
Not ideal for: Large households or homes with multiple simultaneous hot water demands, where higher flow rates are necessary.
- Power Source:240V AC
- Flow Rate:2.68 GPM
- Wattage:11 kW
- Temperature Range:up to 140°F
- Self-Modulating:Yes
- Dimensions:8.25″W x 12.63″H
Bottom line: Best suited for small-scale applications or single fixtures, especially where space and simplicity matter most.
Rheem 18kW 240V Tankless Electric Water Heater, Gray
This Rheem 18kW unit strikes a balance between capacity and installation complexity, making it suitable for mid-sized homes. Its flow rate of 4.4 GPM allows sufficient hot water for multiple fixtures, but it’s less demanding than the Mizudo 36kW for large households. The digital LED display and self-modulating technology enable precise temperature control and energy efficiency, with the ability to cut energy costs by up to half. Its installation requires a dedicated circuit with a 40A breaker and proper wiring, similar to the other Rheem models, but it’s more manageable than the 36kW version. Its durability and safety features make it a dependable choice for those upgrading from traditional tanks. This model is ideal for homes with moderate hot water needs and electrical capacity for a mid-range system.
Pros:- Adequate flow rate for typical family needs
- Digital display for easy temperature adjustments
- Energy-efficient with self-modulating technology
- Compact, space-saving design
Cons:- Installation still requires electrical upgrades
- Limited capacity for larger households
Best for: Medium-sized households with moderate hot water demands, seeking a reliable, space-saving alternative to tank systems.
Not ideal for: Large households with high simultaneous hot water needs or homes lacking sufficient electrical infrastructure.
- Power Source:240V AC
- Flow Rate:4.4 GPM
- Wattage:18 kW
- Temperature Range:up to 140°F
- Self-Modulating:Yes
- Dimensions:14.5″W x 18.25″H
Bottom line: This unit offers a solid middle ground for households needing reliable hot water without the complexity of very high wattage systems.
How We Picked
Products were evaluated based on performance capacity, energy efficiency, ease of installation, build quality, and feature set. We prioritized units with sufficient flow rates for whole house use, considering typical household demands and the need for reliable hot water. Cost-effectiveness was also a key factor, balancing initial investment against long-term savings. We ranked models that offer straightforward installation and maintenance, with a focus on safety certifications like ETL. The goal was to highlight options suitable for a range of budgets and household sizes, from smaller homes to larger families requiring higher flow rates.Factors to Consider When Choosing Best Electric Tankless Water Heater For Whole House Use
Choosing the best electric tankless water heater for whole house use requires understanding several key factors. These units must meet your household’s hot water demand, fit your electrical system, and suit your budget. Beyond features, it’s vital to consider long-term energy savings, installation complexity, and durability. Making an informed decision ensures you select a model that balances performance with cost, avoiding common pitfalls like under-sizing or overpaying for unnecessary features.Flow Rate and Capacity
Flow rate determines how many fixtures can run simultaneously without a drop in water temperature. For whole house use, aim for units that deliver at least 4 GPM, with larger households needing closer to 8 GPM. Overestimating capacity can lead to unnecessary costs, while underestimating results in cold showers. Consider your household’s peak demand and choose a unit that can comfortably handle multiple simultaneous uses, factoring in shower, dishwasher, and laundry needs.
Electrical Requirements
Most high-capacity units require substantial electrical service, often 240V with a dedicated circuit. Check your home’s electrical panel to ensure it can support the wattage load, especially for 27kW or higher models. Some units, like the Mizudo 36kW, may need upgrades to your electrical system, adding to installation costs. Conversely, smaller models with lower wattage are easier to install but may not meet your entire household’s demands.
Energy Efficiency and Operating Costs
Many modern units include self-modulating technology that adjusts power based on demand, reducing energy waste. Features like digital temperature controls and insulation also improve efficiency. While these add to the initial price, they can lower your utility bills over time. Be mindful that higher-capacity units tend to consume more energy, so balancing capacity with efficiency is key to long-term savings.
Size, Installation, and Space
Compact models are ideal for homes with limited space or for point-of-use applications. Larger units often require significant installation work, including electrical upgrades and dedicated space. Consider your available space and whether you prefer a wall-mounted unit that blends into your home or a more accessible model. Proper installation not only ensures safety but also maximizes the lifespan of your heater.
Cost, Warranty, and Features
While initial price varies widely, investing in a reputable brand with a solid warranty can save money over time. Additional features like WiFi control, LED displays, and digital temperature adjustments add convenience but may increase cost. Think about which features matter most for your lifestyle and whether they justify the extra expense. Always review warranty coverage to protect your investment against potential defects or failures.
Frequently Asked Questions
Can I install a tankless water heater myself?
Installing a whole house electric tankless water heater typically requires electrical expertise, especially for units with high wattage demands. Many models need dedicated circuits and electrical panel upgrades, which should be handled by licensed professionals. Incorrect installation can lead to safety hazards, poor performance, or voided warranties. For most homeowners, hiring a qualified electrician ensures compliance with local codes and optimal operation.
How do I know if my electrical system can support a high-capacity unit?
Check your electrical panel for available capacity and existing circuits. High-wattage units like 27kW or 36kW typically need a 240V supply with a dedicated circuit rated for 100A or more. If your panel lacks sufficient capacity, you might need an upgrade, which adds to the overall cost. Consulting a licensed electrician can provide a precise assessment and help you plan for any necessary electrical work.
What is the typical lifespan of an electric tankless water heater?
Most quality electric tankless water heaters last between 20 to 25 years with proper maintenance. They are generally more durable than traditional tank models because they have fewer parts prone to corrosion. Regular flushing to prevent mineral buildup and checking electrical connections can extend their lifespan. Investing in a reputable brand with a good warranty can also provide peace of mind over the long term.
Are there any safety concerns with high-wattage units?
High-wattage electric tankless heaters pose potential electrical hazards if not installed correctly. Proper grounding, circuit protection, and adherence to local electrical codes are essential. Overloading circuits or poor wiring can lead to short circuits or fire risks. Always use a licensed electrician for installation and regular inspections to maintain safety standards.
How much can I save on energy bills with a tankless water heater?
Tankless water heaters generally consume less energy than traditional tank models because they heat water on demand. Savings depend on usage patterns, but many households see a 20-30% reduction in water heating costs. Features like self-modulation further enhance efficiency by reducing unnecessary power consumption. Keep in mind that the initial investment might be higher, but energy savings over time can offset this difference.
Conclusion
For most households, the Rheem RTEX-24 offers a reliable balance of capacity, ease of installation, and cost, making it the best overall pick. Homeowners seeking maximum flow rates and willing to upgrade their electrical system should consider the Mizudo 36kW, which excels in large households or those with high hot water demands. Budget-conscious buyers or those with smaller homes may find the WINTEMP 18kW sufficient, especially with its smart features. Beginners or those replacing an existing unit should prioritize models with straightforward installation, while premium buyers might prefer units with advanced controls and extended warranties. Ultimately, your choice depends on your household size, electrical setup, and long-term goals for efficiency and convenience.
