The best efficient gas water heater depends on household demand, installation location, and verified efficiency information. Among these five options, ThermoMate is the clearest choice for shoppers prioritizing a stated thermal-efficiency figure; Rheem offers a higher listed flow rate, while APUS is specifically an outdoor model. Compare capacity and installation requirements before choosing, since a product’s BTU rating alone does not establish energy efficiency.
| Product | Best For | Key Listed Detail |
|---|---|---|
| APUS Natural Gas Tankless | Outdoor installation | 190,000 BTU |
| VEVOR Gas Tankless | Temperature controls | 100,000 BTU; ±1°F control |
| CAMPLUX Natural Gas | Higher stated flow | Up to 6 GPM; 150,000 BTU |
| ThermoMate CZ422NG | Efficiency data and safeguards | Up to 98% thermal efficiency; up to 5 GPM |
| Rheem RTG Series | Higher stated flow capacity | Up to 7.0 GPM; 160,000 BTU |
APUS 190,000 BTU Outdoor Tankless Water Heater
Best for: Buyers who need an outdoor natural-gas tankless unit and are comparing models by burner input. The listed name specifies outdoor use and a 190,000 BTU rating, making installation location the clearest reason to consider it.
Why it was selected: It is the only product in this selection explicitly identified as outdoor. Confirm that an outdoor model suits the home’s layout and local installation requirements before purchase.
Limitation: The supplied product information does not state flow rate, thermal efficiency, or UEF, so it cannot be ranked against models with those figures using efficiency data alone.
VEVOR 100,000 BTU Gas Tankless Water Heater
Best for: Buyers who value accessible controls and precise temperature adjustment. VEVOR lists smart temperature control with ±1°F precision, a large LED display, and a touch panel that shows water temperature and operating status.
Why it was selected: Its listed 100,000 BTU/h input and 4.3-gallon designation provide useful comparison points, while the interface and temperature-control features distinguish it from models whose supplied descriptions give fewer control details.
Limitation: The provided information does not give a GPM rating or thermal-efficiency figure. Check the manufacturer’s sizing and installation details to determine whether its capacity fits the household.
CAMPLUX 6 GPM Natural Gas Tankless Heater
Best for: Households comparing options by stated hot-water flow. This indoor natural-gas model is listed at up to 6 GPM and 150,000 BTU, giving shoppers clear capacity figures to compare with their expected simultaneous hot-water use.
Why it was selected: Its listed flow rate is higher than the ThermoMate’s stated maximum, while its BTU input is below the Rheem model’s listed input. These numbers help narrow a shortlist but do not establish actual output under every water temperature or flow condition.
Limitation: The supplied product information does not include a UEF or thermal-efficiency percentage, so compare verified efficiency documentation before choosing it specifically to reduce energy use.
ThermoMate CZ422NG 5 GPM Tankless Heater
Best for: Shoppers who want a listed efficiency figure alongside flow and temperature-control specifications. ThermoMate reports up to 98% thermal efficiency, a UEF of 0.81, up to 5 GPM, and 113,000 BTU.
Why it was selected: It provides more explicit efficiency information than the other supplied product descriptions. The listing also describes ±1°F temperature consistency, an oxygen-free copper heat exchanger, and multiple safety protections, including freeze protection that activates at 41°F.
Limitation: Its listed maximum flow is lower than the CAMPLUX and Rheem models. The stated two-shower performance is based on a 65°F inlet temperature and a 105°F outlet, so household conditions matter.
Rheem RTG Series 7 GPM Natural Gas Heater
Best for: Buyers whose priority is a higher stated flow capacity. Rheem lists up to 7.0 GPM and 160,000 BTU for this indoor, non-condensing, on-demand natural-gas model.
Why it was selected: Its listed maximum flow is the highest among these five products, making it a relevant option for shoppers evaluating higher-demand households. The non-condensing design is an important specification to discuss with an installer when comparing venting and installation needs.
Limitation: The supplied details do not include a UEF or thermal-efficiency percentage. Do not treat the “high efficiency” wording in the name as a substitute for comparing verified efficiency figures.
Buying Guide: How to Choose an Efficient Gas Water Heater
Which efficiency rating should you compare?
Look for the Uniform Energy Factor (UEF) or a clearly stated thermal-efficiency percentage in the product documentation. These figures are more useful for comparing energy performance than BTU input alone. In this selection, ThermoMate lists a UEF of 0.81 and up to 98% thermal efficiency; the other supplied descriptions do not provide comparable figures.
How much flow does your household need?
Estimate how many hot-water fixtures may run at once, then compare their combined demand with a heater’s rated GPM. The listed maximums here range from 5 GPM for ThermoMate to 7 GPM for Rheem, with CAMPLUX at up to 6 GPM. Actual output can depend on incoming water temperature and the temperature rise required, so confirm sizing with the manufacturer or a qualified installer.
Does the installation location affect the choice?
Yes. The APUS is identified as an outdoor unit, while VEVOR, CAMPLUX, ThermoMate, and Rheem are described as indoor models. Venting, gas supply, electrical needs, clearances, and local code requirements should be reviewed before selecting a unit. The Rheem is specifically labeled non-condensing, a detail worth discussing when comparing installation requirements.
Should you choose the highest BTU rating?
Not automatically. BTU indicates input capacity, but it does not independently show annual energy use or prove that a model is the most efficient. Compare verified efficiency ratings, flow capacity, household demand, and installation requirements together.
Frequently Asked Questions
What makes a gas water heater energy efficient?
A higher verified efficiency rating, such as UEF or thermal efficiency, indicates how effectively a model uses its fuel. Compare ratings using the same measurement method.
Is tankless always more efficient than a tank model?
Not in every situation. Efficiency depends on the model, household hot-water use, installation, and operating conditions. Compare the specific product’s verified rating rather than relying only on its tankless design.
Does a higher GPM rating mean lower energy use?
No. GPM describes flow capacity, not energy efficiency. Choose a flow rating that meets household demand, then compare the model’s efficiency information separately.
Which product lists the clearest efficiency figures?
ThermoMate lists up to 98% thermal efficiency and a UEF of 0.81. Confirm those specifications in current product documentation before purchase.
Can an outdoor water heater be installed indoors?
The APUS product is identified as outdoor, so do not assume it is suitable for indoor installation. Check the manufacturer’s instructions and consult a qualified installer about the correct model and location.