Wondering how much propane your tankless water heater will use—and what it will cost to run? Whether you’re planning for a new installation, managing a cabin off-grid, or just trying to budget fuel costs, understanding propane usage is key. This complete guide explains how much propane a tankless water heater really uses, what factors affect consumption, and how to pick a high-efficiency model for maximum savings.
Quick Answer: Typical Propane Use for Tankless Water Heaters
- Average propane tankless water heater: Uses about 1.5–2.5 gallons of propane per hour at full power (max BTU output).
- Normal household: For 2–3 showers and moderate daily use, expect 15–35 gallons per month for hot water only.
- Yearly average: Most families use 150–400 gallons of propane per year for hot water, depending on usage and heater size.
How to Calculate Propane Use for Your Tankless Water Heater
- 1 gallon of propane = 91,500 BTUs
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Example: If your tankless heater is rated at 180,000 BTU/hour:
180,000 BTU ÷ 91,500 BTU/gallon = 1.97 gallons of propane per hour (at full capacity) - Most tankless heaters do not run at full power constantly—average household use is much less.
- To estimate monthly usage: (Gallons per hour) × (hours run per day) × (days per month)
What Affects Propane Usage in Tankless Water Heaters?
- Hot Water Demand: More people and fixtures = higher use.
- BTU Rating: Higher BTU heaters consume more propane per hour at full blast.
- Water Temperature Rise: Colder incoming water = heater works harder and uses more fuel.
- Efficiency (UEF): High-efficiency models get more hot water from each gallon of propane.
- Showers vs. Appliances: Baths, long showers, and washing machines increase total use.
- Recirculation Pumps: Can slightly increase propane use if hot water is kept circulating.
Buyer’s Guide: Choosing a Propane Tankless Water Heater for Maximum Efficiency
- BTU Range: For a large family or multiple bathrooms, pick 150,000–199,000 BTU models. Smaller households can go lower.
- Uniform Energy Factor (UEF): The higher, the better—look for 0.80 or above for gas models.
- Modulating Burners: Units that adjust output to match demand will save propane on lighter loads.
- Condensing Technology: Condensing units capture extra heat from exhaust, boosting efficiency and lowering fuel use.
- Outdoor vs. Indoor: Outdoor models are simpler to install, but all models work similarly in terms of fuel use if properly sized.
- Warranty & Support: Choose a reputable brand with a solid warranty for peace of mind.
Top Propane Tankless Water Heaters: Reviewed
Camplux 5L Outdoor Portable Propane Tankless Water Heater
- 34,000 BTU/hour = 0.37 gallons propane per hour (max)
- Great for cabins, camping, outdoor showers, and RVs
- Lightweight, easy hookup, 1.32 GPM output
Final Verdict: Best for light use or portable setups—super fuel-efficient for small jobs.
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Rinnai V65EP Propane Tankless Water Heater
- 150,000 BTU/hour = 1.64 gallons propane per hour (max)
- 6.5 GPM for 1–2 bathrooms, compact and reliable
- High efficiency, outdoor rated with freeze protection
Final Verdict: Top pick for mid-size homes needing serious hot water and fuel savings.
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Rheem RTG-95XLP High Efficiency Propane Tankless Water Heater
- 199,000 BTU/hour = 2.17 gallons propane per hour (max)
- 9.5 GPM—whole-house power for large families
- Condensing model for extra fuel savings (UEF 0.93)
- Outdoor installation, long warranty
Final Verdict: Best for large families—high flow and high efficiency mean less propane for more hot water.
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Comparison Table: Propane Use by Top Tankless Models
| Model | BTU/hour | Max Propane Use (gal/hr) | Max GPM | Efficiency | Best For | Price Link |
|---|---|---|---|---|---|---|
| Camplux 5L | 34,000 | 0.37 | 1.32 | 0.80 UEF | Outdoor/portable | View |
| Rinnai V65EP | 150,000 | 1.64 | 6.5 | 0.82 UEF | Small family | View |
| Rheem RTG-95XLP | 199,000 | 2.17 | 9.5 | 0.93 UEF | Large family | View |
How to Save Propane With Your Tankless Water Heater
- Install Low-Flow Fixtures: Use 1.5–2.0 GPM showerheads and aerators to cut hot water demand.
- Set Temperature Lower: 120°F is plenty for most homes—higher temps waste fuel.
- Fix Leaks & Insulate Pipes: Prevent waste by fixing dripping faucets and wrapping hot water lines.
- Buy a High-Efficiency Model: Condensing heaters use less propane for the same amount of hot water.
- Use Recirculation Pumps Wisely: Only run them when needed to avoid excess propane use.
FAQ: Propane Use & Tankless Water Heaters
- How long does a 100-gallon propane tank last for hot water?
For a typical family using 1.5–2 gallons/day, a 100-gallon tank lasts about 1–2 months for hot water only. - Is propane or natural gas more efficient?
Both fuel types offer similar efficiency if the heater is well designed. Propane is often used where natural gas isn’t available. - How can I check my real usage?
Monitor your tank gauge, and track how long it takes to use up a set amount during normal use for your home. - Do tankless heaters use propane when off?
No. They only burn fuel when hot water is running—no standby usage. - Is propane expensive to run for a whole house?
It depends on local propane prices, your heater’s efficiency, and your water use. Tankless models are generally cheaper to operate than tank water heaters for most families.
Conclusion
Propane tankless water heaters are efficient, powerful, and cost-effective for hot water—especially where natural gas isn’t available. Know your model’s BTU rating, estimate usage with the formulas above, and pick a high-efficiency unit for the best savings. Want help sizing your system, comparing costs, or finding the right propane heater for your home or cabin? Reach out anytime for advice!