Choosing a most efficient natural gas heater depends on whether you need space heating or on-demand hot water. Below is a concise comparison of five high-efficiency natural gas heaters selected for energy performance, features, and installation types. Use the table to compare key specs at a glance, then read individual product breakdowns and a buying guide to decide which model fits your needs.
| Product | Type | Max BTU | Flow / Coverage | Notable Efficiency Feature |
|---|---|---|---|---|
| Rheem Condensing Tankless | Condensing Tankless Water Heater | 180,000 BTU | 0.4–9 GPM | Condensing design for higher recovery |
| FOGATTI InstaGas 170 | Tankless Water Heater | 170,000 BTU | Up To 7.5 GPM | Four-stage combustion and precise temp control |
| Orbek 100K Tankless | Tankless Water Heater | 100,000 BTU | Up To 4.3 GPM | Oxygen-free copper heat exchanger |
| VELPAX 20L Outdoor | Outdoor Tankless Water Heater | 120,000 BTU | 5.26 GPM | Multiple safety protections, stainless body |
| ProCom MN300TPA-B | Ventless Infrared Space Heater | 30,000 BTU | Up To 1,400 Sq. Ft. | No electricity required; infrared heat |
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Rheem Natural Gas Condensing Tankless Water Heater
This condensing tankless water heater from Rheem offers a high continuous output and is built for efficiency. Its flow rate of 0.4–9 GPM supports multiple simultaneous uses in many homes. The 180,000 BTU input capacity combined with condensing technology recovers heat from exhaust gases, improving thermal efficiency compared to non-condensing models.
Temperature settings range from 100°F to 140°F with a factory default of 120°F, and the unit includes electric ignition for reliable starts. This model is best suited for indoor installation and homes that need a high-flow solution while prioritizing energy recovery. Installation requires proper venting and gas sizing to achieve rated performance.
FOGATTI Natural Gas Tankless Water Heater
The FOGATTI InstaGas Comfort 170 Series is a high-output tankless water heater with 170,000 BTU and a maximum 7.5 GPM flow. It emphasizes compact installation and rapid recovery, claiming space savings versus traditional tanks and a design intended for multitasking households.
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Key features include precision temperature control via water servo technology and sensors to keep water temperature within ±1°F under varying loads. The four-stage combustion system aims to maintain consistent heat delivery and combustion efficiency across conditions. Suitable for indoor mounting, this unit targets users needing high, steady hot water demand with fine temperature stability.
Orbek Natural Gas Tankless Water Heater 100K
The Orbek 100,000 BTU tankless unit provides up to 4.3 GPM, suitable for small to medium households or point-of-use installs. It’s CSA certified and presents multiple built-in safety protections, including dry combustion, overheat, leakage, and flame failure protections to enhance reliability and safe operation.
Construction includes an oxygen-free copper heat exchanger intended to improve heat transfer and corrosion resistance. The heater offers three heating modes to match seasonal needs and optimize energy use. This product targets owners seeking a compact, safety-focused tankless solution that balances efficiency and durability.
VELPAX Outdoor Natural Gas Tankless Water Heater
The VELPAX outdoor tankless water heater is designed for external installation and provides up to 5.26 GPM with a 120,000 BTU burner. It features a stainless steel body and an oxygen-free copper core to resist corrosion and minimize heat loss.
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Safety and control features include digital Fahrenheit display and protections such as flame failure, anti-freeze, and overheat devices. Its combustion technology aims to reduce gas consumption and noise. Outdoor placement reduces venting complexity and heat-exchange losses inside living spaces, making it an efficient option where outdoor mounting is feasible.
ProCom MN300TPA-B Ventless Infrared Space Heater
The ProCom MN300TPA-B is a ventless infrared space heater delivering up to 30,000 BTU and rated to heat areas up to 1,400 sq. ft. It uses infrared radiant heating to warm objects and occupants directly rather than convecting air, which can feel more efficient in certain room layouts.
This model includes thermostat control with multiple heat settings and can be wall-mounted or floor-placed with included hardware. It operates without electricity and incorporates safety features like an oxygen depletion sensor. Ventless heaters offer high in-room efficiency but require attention to ventilation and local codes due to combustion byproducts.
Buying Guide: How To Choose The Most Efficient Natural Gas Heater
Selecting the most efficient natural gas heater involves evaluating type, efficiency metrics, installation constraints, and safety. Below are core considerations and comparison perspectives to guide a purchase.
1. Heater Type And Intended Use
- Tankless Water Heaters — Best For On-Demand Hot Water; efficiency measured by energy factor and condensing vs non-condensing design. Condensing units recover exhaust heat for higher efficiency.
- Space Heaters (Ventless/Infrared) — Good For Direct Room Heating; high in-room efficiency but may increase indoor combustion byproducts and humidity.
- Unit Heaters — Designed For Garages, Workshops, Or Large Spaces; typically high BTU output but require appropriate venting and clearances.
2. Efficiency Features To Prioritize
- Condensing Technology — Recovers latent heat from exhaust; improves thermal efficiency notably for water heaters.
- High AFUE / Energy Factor — For space heaters look for high AFUE; for water heaters look for high energy factor or stated recovery efficiency.
- Precise Temperature Control — Servo-controlled sensors and digital controls reduce overshoot and energy waste.
- Heat Exchanger Material — Copper or stainless components reduce corrosion and maintain heat transfer efficiency over time.
3. Capacity And Load Matching
- For Water Heaters — Match GPM to simultaneous fixture demand. Larger BTU with condensing tech can supply higher flows while maintaining efficiency.
- For Space Heating — Match BTU output to conditioned square footage, factoring insulation, ceiling height, and desired temperature rise.
4. Installation, Venting, And Location
- Indoor Vs Outdoor — Outdoor tankless units simplify venting but may be affected by weather. Indoor condensing models need proper drain for condensate and high-efficiency venting.
- Venting Requirements — Condensing units use PVC or stainless venting; non-condensing may need higher-temperature materials. Ventless space heaters require adherence to local codes.
- Gas Line Sizing — High-BTU units may require larger gas lines and proper regulator sizing to achieve rated performance.
5. Safety And Code Compliance
- Oxygen Depletion Sensor (ODS) — Important for ventless heaters to cut gas if oxygen falls below safe levels.
- Protections — Look for flame failure, overheat, and freeze protection on tankless models. CSA or other certifications indicate tested safety standards.
- Local Codes — Many jurisdictions restrict ventless heaters in bedrooms or tightly sealed homes; check local building regulations before purchase.
6. Long-Term Operating Costs And Maintenance
- Fuel Efficiency Versus Usage Pattern — Condensing tankless units often return higher lifecycle efficiency for continuous domestic hot water usage.
- Routine Maintenance — Descaling, vent checks, and burner inspections preserve efficiency. Heat exchanger material affects longevity and maintenance frequency.
- Installation Costs — Higher-efficiency models may require more complex venting or condensate drainage, influencing upfront costs though lowering operating expense.
7. Comparison Perspectives
- Performance Per BTU — Compare how effectively a unit converts fuel into usable heat; condensing units convert a greater share of fuel energy into hot water or space heat.
- Practical Efficiency — Consider distribution losses: an outdoor tankless avoids indoor distribution loss, while a centrally located unit may reduce piping losses for multi-bath homes.
- Comfort And Response — Infrared heaters deliver radiative comfort quickly for occupants, while tankless systems provide constant hot water without storage loss.
Use the product comparisons and these buying criteria to determine which model aligns with your household demand, installation possibilities, and efficiency goals. Professional sizing and installation are recommended to ensure safety, code compliance, and the highest operational efficiency.
Tips for Getting the Best HVAC Prices
- Prioritize Quality Over Cost
The most critical factor in any HVAC project is the quality of the installation. Don’t compromise on contractor expertise just to save money. - Check for Rebates
Always research current rebates and incentives — they can significantly reduce your overall cost. - Compare Multiple Quotes
Request at least three estimates before making your choice. You can click here to get three free quotes from local professionals. These quotes include available rebates and tax credits and automatically exclude unqualified contractors. - Negotiate Smartly
Once you've chosen a contractor, use the proven strategies from our guide — How Homeowners Can Negotiate with HVAC Dealers — to get the best possible final price.