Rheem Tankless Water Heater Size Calculator
Determine which Rheem tankless water heater model is right for your home based on your hot water needs.
How to Choose the Right Rheem Tankless Water Heater
Rheem offers one of the most comprehensive lines of tankless water heaters in North America, with models ranging from compact point-of-use electric units to high-performance whole-home gas systems. Selecting the right Rheem tankless water heater involves understanding your household's peak hot water demand, your local climate conditions (which affect inlet water temperature), and your home's fuel type availability.
Rheem Tankless Product Lines
Rheem manufactures several series of tankless water heaters, each designed for specific applications:
Gas Models
- Prestige Series: High-efficiency condensing models (up to 96% efficiency) with WiFi capability
- Performance Platinum: Non-condensing models with durable heat exchangers
- RTG Series: Outdoor models that save indoor space
Electric Models
- RTEX Series: Whole-house electric models with advanced flow control
- Point-of-Use: Compact units for single fixture applications
Sizing Factors for Rheem Tankless Heaters
Rheem tankless water heaters are sized based on three primary factors:
- Flow Rate (GPM): The total gallons per minute of hot water needed during peak usage
- Temperature Rise: The difference between incoming groundwater temperature and desired output temperature
- Fuel Type Capacity: Gas models are rated in BTU/hr while electric models are rated in kW
Typical Rheem Model Capacities
| Model Series | Flow Rate (GPM) | BTU (Gas) or kW (Electric) | Bathrooms Supported |
|---|---|---|---|
| Prestige 199k | Up to 11 GPM | 199,000 BTU | 3-4 bathrooms |
| Performance 180k | Up to 8.4 GPM | 180,000 BTU | 2-3 bathrooms |
| RTEX-36 | Up to 7.2 GPM | 36 kW | 2 bathrooms |
| RTG-95 | Up to 9.5 GPM | 199,000 BTU | 3-4 bathrooms |
Gas vs Electric Rheem Models
Gas models (natural gas or propane) are generally better for whole-home applications, especially in colder climates. Rheem's high-efficiency condensing models can achieve up to 96% energy efficiency and qualify for ENERGY STAR certification.
Electric models are ideal for point-of-use applications or smaller homes in moderate climates. Rheem's RTEX series features self-modulating technology and compact designs that are easier to install than gas models.
Rheem-Specific Features to Consider
- EcoNet WiFi: Available on Prestige series for remote control and monitoring
- Scale Detection: Advanced systems that alert you to potential mineral buildup
- Recirculation Options: Compatible with Rheem's tankless recirculation systems
- Warranty: Rheem offers industry-leading warranties (up to 12 years on heat exchangers)
- Low NOx: California-compliant models available
Installation Considerations for Rheem Units
Proper installation is crucial for optimal performance of Rheem tankless water heaters:
- Gas Models: Require proper venting (stainless steel for condensing models) and gas line sizing
- Electric Models: Need adequate electrical service and proper circuit protection
- Water Quality: Hard water may require a water softener to prevent scale buildup
- Freeze Protection: Rheem offers freeze-protected models for cold climates
- Professional Installation: Recommended to maintain warranty coverage
Rheem Tankless Water Heater Benefits
Advantages
- Industry-leading warranties
- High efficiency models available
- Smart home integration options
- Wide range of sizes and configurations
- Durable construction with copper heat exchangers
- Made in the USA (most models)
Considerations
- Premium pricing for high-end models
- May require professional maintenance
- Gas models need proper venting
- Electric models require substantial power
- Limited low-flow performance on some models
Frequently Asked Questions
What's the most popular Rheem tankless water heater?
The Rheem RTGH-95DVLN (Prestige series) is a best-selling 9.5 GPM natural gas model with 94% efficiency and WiFi capability.
How long do Rheem tankless water heaters last?
With proper maintenance, Rheem tankless heaters typically last 15-20 years, significantly longer than tank-type heaters.
Do Rheem tankless water heaters work in cold climates?
Yes, Rheem offers freeze-protected models that can operate in temperatures as low as -30°F when properly installed.
Can I install a Rheem tankless water heater myself?
While possible for experienced DIYers, professional installation is recommended to ensure proper setup and maintain warranty coverage.
How often should I flush my Rheem tankless water heater?
Rheem recommends annual flushing for most installations, or every 6 months in areas with very hard water.
Conclusion
Rheem tankless water heaters offer reliable, efficient hot water solutions for homes of all sizes. Use our calculator above to identify which Rheem models match your household's needs based on your number of bathrooms, climate conditions, and fuel type. Remember that proper sizing and professional installation are key to getting the best performance from your Rheem tankless water heater.