If you’ve ever been halfway through a hot shower only to have the water turn ice-cold, you know how important a reliable water heater is. For many households, a natural gas tankless water heater is the perfect solution—delivering endless hot water, high efficiency, and long-term savings. But with so many models on the market, which one is truly the best in 2025?
This guide will walk you through the top choices, what makes them stand out, and how to choose the right one for your home. And at the end, we’ll cover a crucial but often overlooked part of your plumbing system that could save you from thousands of dollars in unexpected repairs.
Why Choose Natural Gas for Your Tankless Water Heater?
While electric tankless water heaters have their place, natural gas models dominate in households that need high output and fast recovery times. Here’s why many homeowners prefer them:
- Higher flow rates: Handles multiple showers or appliances running at once.
- Better performance in cold climates: Gas heats water quickly, even when incoming water is near freezing.
- Lower long-term operating costs: In many areas, natural gas is cheaper per BTU than electricity.
- Durability: Many models last 20 years or more with proper maintenance.
The main trade-off is that they require proper venting and professional installation, but the performance benefits often outweigh the setup cost.
Best Natural Gas Tankless Water Heater Overall: Rinnai RU199iN Super High Efficiency Plus
In 2025, the Rinnai RU199iN continues to be the gold standard for natural gas tankless water heaters. Trusted by installers and loved by homeowners, it offers an unbeatable balance of power, efficiency, and reliability.
- Flow rate up to 11 gallons per minute (GPM) – ideal for large families.
- ENERGY STAR® certified with condensing technology for lower energy bills.
- Compact wall-mounted design saves space.
- Backed by one of the best warranties in the industry.
It’s powerful enough to run multiple showers and appliances simultaneously, even in cold weather, making it perfect for busy households.
Other Top Natural Gas Tankless Water Heaters
Noritz EZ Series
The Noritz EZ Series is designed for easy replacement of old tank-style heaters. It boasts high efficiency, durable construction, and excellent performance in cold climates. The brand is well-known for its long-lasting reliability.
Navien NPE-240A2
Navien’s NPE-240A2 comes with a built-in recirculation system, delivering hot water to taps faster and reducing water waste. It’s highly efficient and perfect for homes where hot water demand is spread across multiple fixtures.
Rheem Performance Platinum 9.5 GPM
This Rheem model combines strong performance with smart technology, including Wi-Fi controls for remote operation. It’s a great choice for tech-savvy homeowners who want control over their water heating from anywhere.
Bosch Therm 940 ES
With German engineering and a reputation for durability, Bosch’s Therm 940 ES is a solid contender for high-demand households. While it’s not as compact as some competitors, it’s built for long-term, reliable performance.
How to Choose the Right Natural Gas Tankless Water Heater
Here are the most important factors to consider when picking your heater:
- Flow rate (GPM): Match the GPM to your household’s peak hot water demand.
- Climate: Colder water coming in requires more powerful heating capacity.
- Gas type: Ensure the unit is compatible with natural gas, not propane.
- Space: Wall-mounted designs save room in smaller utility areas.
- Budget: Higher-end models may cost more initially but save money in efficiency and maintenance.
Pro Tip: Have your gas line inspected before installation—some high-capacity models require larger gas lines than older systems.
Installation and Maintenance Tips
Professional installation is essential for safety and efficiency. Proper venting, correct gas line sizing, and secure water connections are critical to performance. Once installed, maintenance is straightforward:
- Flush the heat exchanger annually to prevent scale buildup.
- Clean or replace intake filters regularly.
- Inspect venting and connections for any signs of wear.
Following the manufacturer’s maintenance schedule will help your unit last for decades.
The Overlooked Side of Home Water Systems
While a natural gas tankless water heater ensures you always have hot water, what happens to that water after it goes down the drain is equally important. If you have a septic system, ignoring it can lead to slow drains, foul smells, and costly repairs.
Many homeowners don’t think about septic maintenance until it’s too late. By then, you could be looking at thousands of dollars in repairs or replacements.
SEPTIFIX – The #1 Septic Tank Treatment
SEPTIFIX is the leading septic tank treatment in the US, trusted by homeowners to keep their systems clean, odor-free, and efficient. These easy-to-use tablets dissolve in your toilet, releasing oxygen and beneficial bacteria that break down waste, sludge, and grease.
Benefits include:
- Neutralizes odors within days.
- Prevents costly pump-outs and backups.
- Safe for all septic systems and environmentally friendly.
- One tablet a month is all you need—just flush and forget.
By combining your new natural gas tankless water heater with proper septic care, you ensure your home’s water system runs smoothly from start to finish.
Final Thoughts
In 2025, the Rinnai RU199iN stands out as the best natural gas tankless water heater for most homes, thanks to its high flow rate, energy efficiency, and proven reliability. However, Noritz, Navien, Rheem, and Bosch also offer excellent models worth considering based on your budget and household needs.
And remember—hot water is only part of the equation. Keeping your septic system healthy with SEPTIFIX ensures you won’t face unpleasant surprises down the line.
Click Here to Get SEPTIFIX – Keep Your Septic Tank Clean and Odor-Free
Endless hot water is great. Endless hot water without septic problems? That’s even better.