Natural Gas vs Propane Fireplace Costs: Monthly & Long-Term

When choosing a gas fireplace, most homeowners focus on flame appearance, BTU output, or installation style.

But over time, fuel cost becomes one of the biggest deciding factors — especially if the fireplace is used regularly for heating.

Natural gas and propane are both common fuels for indoor gas fireplaces, yet they differ significantly in price structure, billing models, refill frequency, and long-term predictability.

While the initial aesthetic of browsing for a high-efficiency gas fireplace draws you in, the operating costs are what you live with daily.

This guide breaks down natural gas vs propane fireplace costs using real-world numbers, monthly usage examples, and long-term ownership scenarios — so you can understand not just which fuel is cheaper today, but which one makes financial sense over years of use.

If you want help estimating costs for your specific home or usage pattern, our team is available at support@pureflameco.com or +1-833-922-6460.

How Fireplace Fuel Costs Are Calculated

Before comparing fuels, it’s important to understand how fireplace operating costs are measured.

Key Cost Variables

• BTU rating of the fireplace: This determines how much fuel is consumed per hour.
• Hours of use per month: Frequency is the multiplier for all costs.
• Fuel price per unit: The fluctuating market rate for therms or gallons.
• Efficiency of the fireplace: How much fuel is converted to usable heat versus waste.
• Delivery or service fees (propane only): Hidden logistics costs.

Fireplace fuel costs are not flat — they scale with how often and how intensely you use the fireplace.

Properly understanding how BTU ratings dictate fuel consumption is the first step in creating a realistic budget.

Fuel Pricing Basics: Natural Gas vs Propane

To accurately compare costs, one must look at the chemical and thermal differences between propane and natural gas, as these dictate how they are sold and measured.

Natural Gas Pricing

• Billed by the therm (100,000 BTUs)
• Delivered continuously via underground pipeline
• Monthly utility bill
• Price varies by region but is generally stable

Propane Pricing

• Billed by the gallon
• Stored in an on-site tank
• Requires scheduled refills
• Price fluctuates seasonally and regionally

Energy content comparison:

• 1 therm of natural gas ≈ 100,000 BTUs
• 1 gallon of propane ≈ 91,500 BTUs

Average Fuel Prices (U.S. Estimates)

These are approximate national averages and will vary by region.

Natural Gas $1.20 – $2.00 per therm Some regions slightly higher in winter

Propane $2.50 – $4.50 per gallon Can spike higher during cold seasons or supply shortages

Monthly Cost Comparison (Real Usage Scenarios)

Let’s compare costs using a 30,000 BTU gas fireplace, which is common for indoor zone heating.

For context, a unit like the Empire Rushmore 40 clean face gas fireplace can operate in this range depending on flame modulation settings.

Scenario A: Light Use

2 hours per day | 30 days per month | Total monthly BTUs: ~1.8 million

Natural Gas ~18 therms Monthly cost: $22 – $36

Propane ~20 gallons Monthly cost: $50 – $90

Scenario B: Moderate Use

4 hours per day | 30 days per month | Total monthly BTUs: ~3.6 million

Natural Gas ~36 therms Monthly cost: $43 – $72

Propane ~39 gallons Monthly cost: $100 – $175

Scenario C: Heavy Use (Primary Zone Heating)

6 hours per day | 30 days per month | Total monthly BTUs: ~5.4 million

Natural Gas ~54 therms Monthly cost: $65 – $110

Propane ~59 gallons Monthly cost: $150 – $265

Long-Term Cost Comparison (5-Year Outlook)

Assuming moderate usage for 5 months per year.

Natural Gas (5 Years) Average annual cost: $300 – $450 5-year total: $1,500 – $2,250

Propane (5 Years) Average annual cost: $700 – $1,100 5-year total: $3,500 – $5,500

Result: Natural gas typically costs 40–60% less over time for comparable heat output.

Refill Frequency vs Continuous Supply

Natural Gas

Always available, no refills, no planning required, and no storage limits.

The main hurdle is the initial infrastructure, specifically the cost of running a new natural gas line to your fireplace location, which can be a significant one-time expense.

Propane

Requires monitoring tank levels and refills every few weeks during heavy use. Missed refills can result in no heat, and emergency delivery often costs extra.

Fuel convenience directly affects perceived cost and reliability.

Hidden Costs to Consider

Propane-Specific Costs

• Tank rental fees: Unless you own your tank, you pay a yearly lease.
• Delivery charges: Surcharges for distance or off-hours drops.
• Minimum refill requirements: Buying in bulk to avoid fees.
• Installation: The costs associated with propane tank installation vary based on tank size (100 vs 500 gallon) and whether it is buried or above ground.
• Seasonal price surcharges: Winter rates are often higher.

Natural Gas-Specific Costs

• Fixed monthly utility service fee: You pay this even in summer (though often minimal).
• Higher upfront gas line installation cost: Trenching or piping can be expensive initially.

Price Stability & Predictability

Natural Gas

Historically more stable due to utility-regulated pricing, making budgeting easier.

Propane

Market-driven pricing with strong seasonal swings, making annual costs harder to predict.

If cost certainty matters, natural gas has a clear advantage.

Efficiency Impact on Fuel Costs

A high-efficiency direct-vent fireplace will reduce fuel consumption for both fuels, but it does not eliminate the pricing gap.

Reviewing a guide on fireplace efficiency ratings shows that while modern units waste less heat, the cost of the fuel itself remains the dominant variable.

Even with equal efficiency:

• Propane remains more expensive per BTU
• Natural gas delivers more heat per dollar

When Propane Can Still Make Financial Sense

Propane may still be practical if:

• Natural gas is unavailable in your area.
• Fireplace use is occasional or strictly decorative.
• Installation costs for running a gas line are prohibitive.
• You already use propane for multiple appliances (bulk discount).

Furthermore, if you fall in love with a specific natural gas model but only have propane available, many units can be adapted by installing a gas-to-propane conversion kit, allowing you to use the chassis you want with the fuel you have.

Cost Summary Table

Final Verdict: Which Fuel Costs Less?

For most homeowners who use their indoor gas fireplace regularly, natural gas is significantly cheaper both monthly and long-term.

Propane offers flexibility where natural gas isn’t available, but that flexibility comes with higher operating costs and more planning.

The right fuel choice depends on usage frequency, local fuel prices, and infrastructure, not just the fireplace itself.

For help estimating real costs based on your home, usage habits, and region, contact support@pureflameco.com or call +1-833-922-6460.