Best Tankless Water Heaters of 2025: Complete Buyer’s Guide & Reviews
Why Go Tankless in 2025?
If you’re tired of running out of hot water during your morning shower or shocked by soaring energy bills, a tankless water heater might be the perfect solution. Also known as on-demand water heaters, these units heat water only when you need it, eliminating standby energy losses and providing endless hot water.
Quick Answer: The best tankless water heaters of 2025 combine energy efficiency, smart technology, and reliable performance. Top models from Rinnai, Navien, Rheem, and EcoSmart offer flow rates from 3 to 11+ gallons per minute, with prices ranging from $500 to $2,500 plus installation ($1,000–$3,500).
Benefits at a Glance
- Endless hot water – never run out, even with back-to-back showers
- Energy savings – 24–34% more efficient than tank-style heaters
- Space saving – wall-mounted, frees up floor space
- Longer lifespan – 20+ years vs. 10–15 for tanks
- Smart features – WiFi control, leak detection, voice assistant compatibility
Top 10 Best Tankless Water Heaters of 2025
After extensive research and analysis of hundreds of customer reviews, expert tests, and manufacturer specifications, we’ve selected the best tankless water heaters for every need and budget.
1. Rinnai V65iN – Best Overall Gas Tankless
Price: $900 – $1,100
Flow Rate: 6.5 GPM
Fuel: Natural Gas or Propane
Energy Factor: 0.82
The Rinnai V65iN continues to dominate the market with its legendary reliability and smart home integration. This model features Circ-Logic™ technology that learns your hot water usage patterns and pre-heats water only when needed, saving energy without sacrificing comfort.
Pros:
- Ultra-quiet operation (down to 39 dB)
- Built-in WiFi for control via smartphone or voice
- Compatible with recirculation pumps for instant hot water
- 15-year heat exchanger warranty
Cons:
- Requires professional installation for warranty
- May need two units for large households with simultaneous heavy use
2. Navien NPE-240A – Best Condensing Technology
Price: $1,500 – $1,800
Flow Rate: 8.0 GPM
Fuel: Natural Gas/Propane
Energy Factor: 0.95 (up to 40% more efficient than standard models)
Navien’s condensing technology captures exhaust heat to pre-heat incoming cold water, achieving industry-leading efficiency. The NPE-240A includes a built-in recirculation pump and buffer tank for near-instant hot water at every tap.
Pros:
- EZNav smartphone app for monitoring and diagnostics
- Dual stainless steel heat exchangers for longevity
- Up to 8 simultaneous fixtures (depending on temperature rise)
- 15-year warranty on heat exchanger
Cons:
- Higher upfront cost
- Complex installation may require gas line upgrades
3. Rheem RTEX-18 – Best Electric Tankless for Small Households
Price: $450 – $550
Flow Rate: 4.4 GPM
Fuel: Electric
Energy Factor: 0.99
For apartments, condos, or small homes without natural gas, the Rheem RTEX series offers affordable, efficient on-demand hot water. The RTEX-18 provides enough flow for one shower plus a sink simultaneously.
Pros:
- Compact size (fits in small spaces)
- No venting required – easier installation
- Digital temperature control (80°F–140°F)
- 5-year leak protection warranty
Cons:
- May require 150-amp electrical panel upgrade
- Limited to warm climates (incoming water temp above 50°F)
4. EcoSmart ECO 27 – Best High-Output Electric
Price: $650 – $800
Flow Rate: 6.5 GPM
Fuel: Electric
Energy Factor: 0.99
EcoSmart’s flagship model delivers enough hot water for a 3-bedroom home in moderate climates. Its self-modulating technology adjusts power usage based on flow and temperature, maximizing efficiency.
Pros:
- Works with up to 2 showers simultaneously
- Microprocessor-controlled for precise temperature
- 27 kW output (requires 4x 40-amp breakers)
- Lifetime warranty on the heating chamber
Cons:
- Significant electrical demand
- Not ideal for very cold northern states
5. Takagi T-H3-DV-N – Best Value Gas Tankless
Price: $750 – $900
Flow Rate: 6.6 GPM
Fuel: Natural Gas/Propane
Energy Factor: 0.81
Takagi offers reliable performance at a more accessible price point. The T-H3-DV-N features a dual vent system (direct vent) for flexible installation and a compact design.
Pros:
- 12-year heat exchanger warranty
- Built-in freeze protection for cold climates
- Low NOx emissions (eco-friendly)
- Digital remote control included
Cons:
- Louder operation than premium brands
- Basic smart features (no WiFi)
6. Stiebel Eltron Tempra 29 Plus – Best for Cold Climates (Electric)
Price: $800 – $950
Flow Rate: 5.2 GPM
Fuel: Electric
Energy Factor: 0.99
German-engineered Stiebel Eltron units excel in areas with cold incoming water. The Tempra 29 Plus uses Advanced Flow Control to maintain precise temperature even when water pressure fluctuates.
Pros:
- Maintains temperature within ±1°F
- Works well with well water and hard water
- 7-year warranty
- Sleek, minimalist design
Cons:
- Requires 3x 40-amp breakers (125 amps total)
- Premium price for electric category
7. Rinnai RU199iP – Best for Large Homes
Price: $1,800 – $2,200
Flow Rate: 11.0 GPM
Fuel: Natural Gas/Propane
Energy Factor: 0.82
For mansions or households with multiple bathrooms and appliances, the RU199iP delivers massive flow. It includes a built-in recirculation pump and Ultra Low NOx technology for environmentally conscious buyers.
Pros:
- Handles up to 6 fixtures simultaneously
- WiFi connectivity with Circ-Logic
- 15-year heat exchanger warranty
- Commercial-grade components
Cons:
- 199,000 BTU input may require larger gas line
- Professional installation mandatory
8. Noritz NRC661-DV-NG – Best Durability
Price: $1,000 – $1,200
Flow Rate: 6.6 GPM
Fuel: Natural Gas/Propane
Energy Factor: 0.81
Noritz is known for building tankless water heaters that last decades. The NRC661 features a stainless steel secondary heat exchanger and corrosion-resistant coatings ideal for coastal areas.
Pros:
- 15-year heat exchanger warranty
- EZConnect water connections simplify installation
- Low maintenance design
- Quiet operation
Cons:
- No built-in recirculation (external pump required)
- Basic controller interface
9. AO Smith Signature 900 GPDT-75 – Best Smart Features
Price: $1,300 – $1,600
Flow Rate: 7.5 GPM
Fuel: Natural Gas/Propane
Energy Factor: 0.93
AO Smith’s Signature 900 series integrates seamlessly with smart home ecosystems. The iCOMM® connectivity allows remote temperature adjustment, usage tracking, and maintenance alerts.
Pros:
- Large color touchscreen interface
- Works with Amazon Alexa and Google Assistant
- Self-diagnostic leak detection
- 12-year limited warranty
Cons:
- Premium pricing
- Complex setup for non-tech users
10. Bosch Tronic 3000T – Best Compact Electric
Price: $250 – $350
Flow Rate: 1.8 GPM
Fuel: Electric
Energy Factor: 0.98
For point-of-use applications (under sink, bar, workshop), Bosch’s Tronic 3000T provides instant hot water exactly where needed. It’s perfect for supplementing a main water heater or for small living spaces.
Pros:
- Ultra compact (fits under most sinks)
- Simple installation (plug-in or hardwire)
- Adjustable temperature up to 140°F
- 7-year warranty
Cons:
- Only suitable for 1-2 low-flow fixtures
- Not for whole-house use
Tankless Water Heater Comparison Table (2025)
| Model | Type | GPM | Energy Factor | Price | Best For |
|---|---|---|---|---|---|
| Rinnai V65iN | Gas | 6.5 | 0.82 | $900 | Overall best |
| Navien NPE-240A | Gas (Condensing) | 8.0 | 0.95 | $1,600 | Efficiency king |
| Rheem RTEX-18 | Electric | 4.4 | 0.99 | $500 | Small homes |
| EcoSmart ECO 27 | Electric | 6.5 | 0.99 | $700 | High-output electric |
| Takagi T-H3-DV-N | Gas | 6.6 | 0.81 | $800 | Budget gas |
| Stiebel Eltron Tempra 29 Plus | Electric | 5.2 | 0.99 | $850 | Cold climates |
| Rinnai RU199iP | Gas | 11.0 | 0.82 | $2,000 | Large homes |
| Noritz NRC661 | Gas | 6.6 | 0.81 | $1,100 | Durability |
| AO Smith Signature 900 | Gas | 7.5 | 0.93 | $1,400 | Smart features |
| Bosch Tronic 3000T | Electric | 1.8 | 0.98 | $300 | Point-of-use |
How to Choose the Right Tankless Water Heater
1. Calculate Your Flow Rate (GPM)
Add up the flow rates of fixtures you might use simultaneously:
- Bathroom faucet: 0.5–1.5 GPM
- Kitchen faucet: 1.5–2.2 GPM
- Shower: 1.5–3.0 GPM
- Washing machine: 1.5–3.0 GPM
- Dishwasher: 1.0–2.5 GPM
Example: If you want to run two showers (2.5 GPM each) and a kitchen faucet (2.0 GPM) at the same time, you need at least 7.0 GPM.
2. Consider Temperature Rise
Incoming groundwater temperature varies by region:
- Northern states: 37°F – 50°F (need higher temperature rise)
- Southern states: 60°F – 75°F (lower rise needed)
Most people want water at 120°F. If your incoming water is 45°F, you need a 75°F rise. Higher rise reduces flow rate—check manufacturer charts.
3. Fuel Type: Gas vs. Electric
| Factor | Gas | Electric |
|---|---|---|
| Operating Cost | Lower (gas typically cheaper) | Higher (electricity rates) |
| Installation Cost | Higher (venting, gas line) | Lower (no vent, but may need panel upgrade) |
| Lifespan | 20+ years | 15–20 years |
| Environmental Impact | Produces emissions | Zero emissions (depends on grid) |
4. Venting Options (Gas Models)
- Power vent: Uses fan to push exhaust through PVC pipe (flexible)
- Direct vent: Draws air from outside, exhausts outside (safer, more efficient)
- Condensing: Extracts extra heat, cooler exhaust, can use smaller PVC
5. Smart Features
- WiFi/app control for remote temperature adjustment and monitoring
- Recirculation pump for instant hot water (saves water and time)
- Leak detection automatically shuts off water if a leak is detected
- Voice assistant integration (Alexa, Google Home)
Installation Costs and Requirements
Professional installation is strongly recommended for gas units and often required for warranty. Typical costs:
| Component | Gas Tankless | Electric Tankless |
|---|---|---|
| Unit cost | $800 – $2,500 | $400 – $1,000 |
| Labor | $1,000 – $2,500 | $500 – $1,500 |
| Gas line upgrade | $300 – $1,500 | N/A |
| Electrical upgrade | N/A | $500 – $2,000 |
| Venting materials | $200 – $800 | N/A |
| Permits | $100 – $500 | $50 – $200 |
| Total installed | $2,500 – $6,500 | $1,500 – $4,500 |
Do You Need to Upgrade Your Gas Line or Electrical Panel?
- Gas: Older homes may have 1/2″ gas lines; tankless often needs 3/4″ or 1″ lines. A licensed plumber can assess.
- Electric: Electric tankless units draw 60–150 amps. If your panel is maxed out, you may need a sub-panel or service upgrade ($1,500–$3,000).
Maintenance Tips for Longevity
Tankless water heaters require minimal maintenance but benefit from annual servicing:
- Flush the system with vinegar or descaling solution to remove mineral buildup (especially in hard water areas)
- Clean inlet filter to prevent flow reduction
- Check venting for obstructions or corrosion
- Inspect burners (gas) for proper flame
- Test T&P relief valve annually
Most manufacturers recommend professional maintenance every 1–2 years.
Frequently Asked Questions
Will a tankless water heater save me money?
Yes, over time. Energy savings of 24–34% can reduce annual bills by $100–$300. Combined with a 20+ year lifespan, the payback period is typically 5–10 years depending on usage and local utility rates.
Can I install a tankless water heater myself?
While possible for electric models with electrical experience, gas units require venting and gas line work that is dangerous and often illegal without a license. DIY installation usually voids warranties.
Do tankless water heaters work in cold climates?
Yes, but you may need a larger unit or a model with freeze protection. Some units have built-in heaters to prevent freezing in unheated spaces.
What size tankless water heater do I need for a family of 4?
For a typical 3-bedroom home with 2 bathrooms, look for 6–8 GPM gas units or high-output electric (27+ kW). Consider simultaneous usage patterns.
Are tankless water heaters eligible for tax credits?
Yes! In 2025, ENERGY STAR certified gas tankless water heaters with a UEF ≥ 0.90 may qualify for a federal tax credit of up to $600. Some states and utilities offer additional rebates.
Conclusion: Which Tankless Water Heater Should You Buy?
After comparing top models, our recommendations by scenario:
- Best overall: Rinnai V65iN – perfect blend of reliability, smart features, and value
- Best for efficiency: Navien NPE-240A – condensing technology saves the most energy
- Best electric: EcoSmart ECO 27 – powerful enough for most homes
- Best for large families: Rinnai RU199iP – endless hot water for simultaneous use
- Best budget pick: Takagi T-H3-DV-N – reliable performance at a lower price
Remember to always consult with a licensed plumber to assess your home’s specific requirements and ensure proper installation. A well-chosen tankless water heater will provide comfort, savings, and peace of mind for decades.
