Non-condensing tankless water heaters offer dependable hot water on demand without the complexity and cost of condensing models. They suit large families and homes with multiple simultaneous water uses, delivering up to 9.5 gallons per minute with energy savings around 34% compared to electric tanks.
Choosing the right model means balancing flow rate, fuel type, installation location, and efficiency. This guide highlights top options and what specs matter most to help you avoid costly mistakes in comfort and utility bills.
Comparison of Top Non-Condensing Tankless Water Heaters
| Model | Best for | Flow Rate (GPM) | Fuel Type | Installation Location | Warranty Length | Price |
|---|---|---|---|---|---|---|
| Rheem RTG Series 9.5 GPM Natural Gas Tankless Water Heater | Best for Most Homes | 9.5 | Natural Gas | Indoor | 15 years heat exchanger | Check today’s price |
| Rinnai RE180iP Non-Condensing Propane Tankless Water Heater | Best for Propane Users | 8.5 | Propane | Indoor | 15 years heat exchanger | Check today’s price |
| Rheem RTG Series 8.4 GPM Liquid Propane Tankless Water Heater | Best for Propane, Indoor | 8.4 | Liquid Propane | Indoor | 15 years heat exchanger | Check today’s price |
| Rinnai RE160iP Non-Condensing Propane Tankless Water Heater | Best Compact Propane | 6.1 | Propane | Indoor | 15 years heat exchanger | Check today’s price |
| Rheem RTG Series 8.4 GPM Natural Gas Tankless Water Heater Outdoor | Best Outdoor Natural Gas | 8.4 | Natural Gas | Outdoor | 15 years heat exchanger | Check today’s price |
Top Non-Condensing Tankless Water Heaters for Reliable Hot Water
Rheem RTG Series 9.5 GPM Natural Gas Tankless Water Heater
Rinnai RE180iP Non-Condensing Propane Tankless Water Heater
Rheem RTG Series 8.4 GPM Liquid Propane Tankless Water Heater
Rinnai RE160iP Non-Condensing Propane Tankless Water Heater
Rheem RTG Series 8.4 GPM Natural Gas Tankless Water Heater Outdoor
Match Flow Rate to Your Household’s Hot Water Demand
You size a tankless water heater by gallons per minute (GPM), which measures how much hot water it can provide at once. Running multiple showers or fixtures simultaneously adds their flow rates together. For example, three to four showers need about 8 to 10 GPM, while a small home with one or two bathrooms might only require 5 to 6 GPM.
Undersizing a heater leads to cold water bursts when demand exceeds supply. If your 1.5 GPM kitchen faucet and 2.5 GPM shower run together on a unit rated for 4 GPM, expect a noticeable temperature drop. It’s safer to choose a unit with a slightly higher flow rate than you think you need.
Temperature rise—the difference between your incoming water and desired hot water temperature—also affects flow rate. Cold climates require a larger heater or lower flow to reach 120°F. Say your groundwater is 50°F and you want 120°F at the tap, that’s a 70°F rise. Higher rise means reduced flow capacity at that temperature.
Tankless water heater cost varies mainly by flow rate and fuel type, typically $800 to $1,500 for residential models. Installation costs depend on existing plumbing and venting, usually $1,000 to $2,000. Professional installation ensures safety and code compliance.
Understand Efficiency and What Non-Condensing Means for Costs
Non-condensing tankless water heaters lose more heat through exhaust because their flue gases exit at about 300°F, unlike condensing models that cool exhaust to capture extra heat. This results in lower efficiency, with typical Uniform Energy Factors (UEF) around 0.82, while condensing units can reach 0.90 or higher.
UEF measures how efficiently a heater converts fuel to usable hot water over a typical day. A UEF of 0.82 means 82% of the fuel’s energy heats water; the rest is lost—mostly through hot exhaust gases. Higher UEF means lower fuel costs.
Running cost depends on fuel price and consumption. For example, a non-condensing gas heater with a 199,900 BTU/hr input running 1 hour daily at $1.50 per therm costs about $3.00 a day (199,900 ÷ 100,000 × $1.50). By contrast, an electric storage water heater using 4,500 watts for 3 hours consumes 13.5 kWh; at 17 cents per kWh, that’s about $2.30 per day.
Non-condensing units avoid standby losses by heating water only when you need it, which cuts energy use compared to storage tanks that keep water hot all day.
If you’re comparing condensing vs non-condensing tankless heaters, consider upfront cost against fuel savings. Non-condensing models cost less initially and are simpler, but condensing units save more in fuel over years. For moderate to high use, condensing models generally pay off.
Learn more about the efficiency and maintenance trade-offs from our guide on condensing vs non-condensing water heaters.
Choose Installation Location and Venting with Safety in Mind
Tankless water heaters go where they can get enough air and vent safely—usually near your main water line and a gas connection if applicable.
Indoor non-condensing models require direct venting to the outside using sealed combustion pipes. These vent pipes must be metal and rated to handle exhaust temperatures around 300°F, since non-condensing units produce hotter gases that plastic or lower-grade vents can’t handle.
Outdoor models don’t need venting but must be protected from weather exposure. That means placing them under an eave or in a weatherproof enclosure that doesn’t block airflow.
Clearance to combustibles is crucial. Local codes and the unit’s manual specify minimum distances—often several inches from walls and ceilings—to prevent fire hazards. Never enclose an indoor unit tightly without proper ventilation. Doing so risks carbon monoxide buildup and voids the warranty.
Look for Features That Improve Comfort and Reliability
The best tankless water heater brands offer digital temperature controls accurate to ±1°F. This precision avoids the hot and cold swings that spoil a shower.
Freeze protection is a must if your heater’s in a cold area. It prevents expensive damage by automatically heating internal pipes when temperatures drop near freezing.
Built-in safety features like flame failure protection and multiple sensors monitor combustion and water flow, shutting off the unit if anything goes wrong. These reduce breakdown risks and increase reliability.
Some models add WiFi modules as an option. They let you adjust temperature remotely, get maintenance alerts, and track performance—handy for busy households or second homes.
If you want a tankless water heater with recirculation for instant hot water at your tap, check for models designed to support it or compatible with add-on pumps. This feature improves comfort but usually comes at a higher upfront cost.
Fuel Type and Model Variants Matter More Than You Think
Natural gas tankless water heaters usually deliver higher BTU ratings and flow rates but need a reliable natural gas supply and proper venting. That makes them a strong choice for homes connected to a gas line but less practical where natural gas isn’t available.
Propane tankless water heaters perform similarly to natural gas models, often matching BTU output and flow capacity. However, they require propane tanks and may have venting or clearance requirements that differ from natural gas units, so check your model’s manual closely.
Outdoor tankless water heaters sidestep venting concerns since their exhaust goes directly outside into open air. They need built-in freeze protection and robust weatherproofing to handle winter and rain, which adds to upfront cost but simplifies installation.
| Type | Fuel Source | Venting Needs | Installation Notes |
|---|---|---|---|
| Natural Gas | Natural gas line | Requires venting through wall or chimney | Higher flow, needs gas line access |
| Propane | Propane tank | Venting varies by model | Portable but needs safe propane storage |
| Outdoor Models | Natural gas or propane | No venting needed | Freeze protection and weatherproofing required |
Model variants affect installation complexity and price. Indoor models often cost more to install because of venting and clearance requirements. Outdoor variants save on venting but demand extra protection against cold and moisture.
Lower-cost tankless models tend to compromise on maximum flow rate or warranty length. It pays to balance the upfront price against potential long-term savings from higher flow and better reliability.
For the best affordable tankless water heater, look for a unit that fits your fuel source, meets your household’s flow needs, and has solid warranty coverage. Skipping on venting or fuel compatibility may cost more in the long run.
More Questions, Answered
What is a non-condensing tankless water heater and how does it differ from condensing?
How do I calculate the correct flow rate (GPM) for my home?
Can I install a non-condensing tankless water heater myself?
Are non-condensing tankless water heaters suitable for cold climates?
What maintenance is required to keep my tankless water heater running efficiently?
I am a mechanical engineer and love doing research on different home and outdoor heating options. When I am not working, I love spending time with my family and friends. I also enjoy blogging about my findings and helping others to find the best heating options for their needs.
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