When you need continuous hot water for a busy home, a natural gas or propane tankless unit offers on‑demand warmth with high efficiency. This guide highlights five top options suitable for American homes, spanning outdoor and indoor installations, with notes on ideal buyers, efficiency, and practical limitations. Choose the model that best fits your home’s fuel type, venting needs, and shower load. The following table summarizes the key points for quick comparison.
| Product | Best For | Installation | Notes |
|---|---|---|---|
| Rheem RTG Outdoor 8.4 GPM | Large families needing outdoor option | Outdoor | Vent-free outdoor install; non-condensing |
| Rheem RTGH Indoor 8.4 GPM | Indoor install with venting | Indoor with direct vent | Condensing, high efficiency |
| Rheem RTG Outdoor 7.0 GPM (Propane) | Larger homes with propane supply | Outdoor | Outdoor, propane, non-condensing |
| Westinghouse Indoor 7.9 GPM | Smart‑enabled, indoor use | Indoor | WiFi/voice control, precise temp |
| APUS Propane Tankless 4.42 GPM | Compact propane unit for moderate load | Indoor | Lower flow, efficient; stable temps |
Rheem RTG Series Outdoor 8.4 GPM Gas Tankless
Best for: Large homes with outdoor installation and simultaneous showering needs. This model delivers up to 8.4 GPM at a 35°F rise, with 180,000 BTU/hr. It’s designed for continuous on‑demand hot water and is energy‑efficient for an outdoor unit. The non‑condensing design keeps costs lower upfront but may have higher exhaust temperatures compared with condensing units.
Why chosen: Outdoor installation eliminates venting complexity, and the unit is sized for 3–4 showers at once in typical homes. Its rugged cabinet and wall‑mount capability suit qualified installers seeking a durable outdoor solution with strong flow capacity.
Caution: Outdoor installations require weatherproofing and proper clearance. The non‑condensing design means higher exhaust temperatures and potential efficiency differences compared with condensing models.
Rheem RTGH Indoor 8.4 GPM Condensing Tankless
Best for: Homes that prioritize indoor installation with ultra‑low NOx emissions and high efficiency. This model uses condensing technology and achieves a high 0.93 UEF while delivering 8.4 GPM at a 35°F rise with 157,000 BTU/hr.
Why chosen: Indoor direct‑vent installation limits outdoor exposure and reduces exhaust visibility. The high efficiency translates to noticeable energy savings for multi‑bath homes. It’s well suited for large families with multiple simultaneous hot water demands.
Caution: Indoor installations require proper venting and indoor space planning. Condensing systems need access to condensate management and appropriate clearances for service.
Rheem RTG Outdoor 7.0 GPM Propane Tankless
Best for: Homes that rely on propane and need a robust outdoor tankless unit with outdoor installation. It delivers 7.0 GPM at 35°F rise from 160,000 BTU/hr, suitable for 2–3 simultaneous showers.
Why chosen: Outdoor, outdoor‑venting avoids indoor space constraints and provides reliable hot water without indoor combustion air concerns. The propane model offers good compatibility for rural or off‑grid setups.
Caution: Propane units still require secure, weatherproof mounting and routine maintenance. Non‑condensing design means energy efficiency gains aren’t as high as condensing models.
Westinghouse Indoor Gas Tankless 7.9 GPM
Best for: Tech‑minded households seeking smart control and precise temperature stability. This model supports control via a built‑in WiFi app and voice integration, delivering up to 7.9 GPM and 180,000 BTU.
Why chosen: The self‑modulating technology maintains temperature within ±1°F, delivering steady shower comfort. The smart features enable remote status checks and fault alerts, aiding maintenance planning.
Caution: Ensure your home supports WiFi connectivity in the utility space and confirm compatibility with your smart home system. Indoor use requires proper venting and clearances for safe operation.
APUS Propane Tankless 4.42 GPM Indoor
Best for: Smaller homes or apartments needing a compact propane solution with steady temperatures. It provides 95,000 BTU and 4.42 GPM flow, suitable for 2 showers plus one sink under stable conditions.
Why chosen: The unit uses high‑capacity copper heat exchangers and segmented combustion to achieve up to 98% thermal efficiency (0.81 UEF) and energy savings over standard electric tanks.
Caution: The unit’s lower maximum flow means it’s better for moderate hot water loads. Ensure gas supply and ventilation meet local codes for indoor installation.
Buying Guide: Key Purchase Considerations
What fuel type fits your home?
Natural gas and propane are the most common fuels for tankless units. Natural gas generally offers abundant supply and stable costs, while propane is useful where natural gas isn’t available. Consider your home’s existing gas line capacity and any hookup costs.
Indoor vs. outdoor installation
Outdoor models avoid indoor venting but require weatherproofing and clearances. Indoor units demand venting compatibility (direct vent or condensate management) and space planning for service access.
Condensing vs. non-condensing
Condensing units (higher efficiency) use a secondary heat exchange to reclaim heat and generally reduce energy costs. Non-condensing units are typically simpler and sometimes cheaper upfront but may have higher ongoing energy use.
Flow rate and heating capacity
GPM at a 35°F rise indicates how much hot water the unit can deliver during the coldest times. Match the unit to your household hot water needs—consider the number of simultaneous showers, sinks, and appliances.
Temperature stability and control
Self‑modulating burners and digital controls help maintain steady temperatures. Look for units with tight temperature tolerance (±1°F is common in higher‑end models) to avoid cold shocks during peak usage.
Efficiency metrics
UEF (Uniform Energy Factor) and NOx emissions are important. A higher UEF means better energy performance, while ultra‑low NOx emissions are beneficial for air quality and compliance in certain areas.
Smart features and monitoring
Smart controls, WiFi connectivity, and fault alerts can simplify maintenance and allow remote monitoring of operation and temperatures. Ensure compatibility with your smart home ecosystem if desired.
Installation and maintenance considerations
All tankless units should be installed by a qualified professional. Proper venting, gas line sizing, and clearance requirements affect performance and safety. Plan for routine service to maintain efficiency and longevity.
Frequently Asked Questions
- What is the main difference between condensing and non‑condensing tankless water heaters? Condensing units recover heat from exhaust gases to increase efficiency, while non‑condensing units vent exhaust at higher temperatures with typically lower efficiency.
- How many showers can a 7–8 GPM tankless heater support? It depends on the temperature rise and faucet usage, but most 7–8 GPM units can support 3–4 showers simultaneously at moderate temperatures.
- Can I install a tankless water heater indoors without venting? Indoor installation usually requires a venting solution (direct vent or chimneyless system) and proper clearance; consult local codes and a licensed installer.
- Do tankless heaters save energy compared with electric tanks? Yes, especially gas models with high efficiency, as they heat water on demand rather than maintaining a tank of hot water.
- What should I consider when choosing between outdoor and indoor models? Outdoor units avoid indoor venting and space constraints but require weatherproofing; indoor units offer centralized placement with venting but require adequate space and condensate management.