Updated 1/18/24!

Natural Gas Price (Avg.)

Propane Price (Avg.)

$ 1.03 per gallon

$ 2.17 per gallon

Currently, in Montana, natural gas is cheaper per gallon equivalent compared to propane. However, it’s important to consider the efficiency of the fuel in the specific application (like a generator), as natural gas and propane have different efficiencies and energy densities.

Natural Gas vs. Propane - Which is Best for You?

Natural Gas

  1. Cost: Natural gas is generally cheaper per gallon than propane, but it is less efficient. For example, a natural gas furnace burns around 97 cubic feet per hour to produce the same energy that a propane furnace would generate using only 40 cubic feet.
  2. Efficiency: Natural gas burns more volume per hour than propane but delivers fewer BTUs.
  3. Supply: Natural gas is supplied via pipelines, offering a constant supply as long as there is sufficient pressure in the gas lines.
  4. Environmental Impact: It produces fewer harmful emissions than diesel and gasoline but is not entirely harmless. Propane is considered more environmentally friendly.
  5. Safety: Natural gas dissipates more quickly into the atmosphere than propane, which can be seen as a safety advantage.
Natural Gas Pros & Cons

(On full-load, a 20kW natural-gas fueled generator would likely require 442 ccf per hour. (Approx. $4.78))


  1. Cost: Propane tends to be more expensive per gallon than natural gas. However, it’s more energy-efficient, meaning you need less of it to produce the same amount of energy.
  2. Efficiency: Propane has a higher energy density compared to natural gas. One cubic foot of propane equals about 2,500 BTUs, while one cubic foot of natural gas offers around 1,000 BTUs.
  3. Storage and Supply: Propane is stored in tanks and is convenient for areas without natural gas lines. However, it requires regular refilling, and tanks must be stored safely.
  4. Environmental Impact: Propane burns cleanly with low carbon monoxide levels and adds minimal toxicity to the environment.
  5. Safety: Propane is less flammable than gasoline and won’t ignite until it reaches 500 degrees Celsius.

(On full-load, a 20kW propane fueled generator would likely require 5 gallons per hour. (Approx. $10.85))


  • The cost-effectiveness of using natural gas versus propane for generators can be close. While natural gas is cheaper per unit, it is less efficient compared to propane.
  • The decision may depend on local fuel prices, availability, and specific generator models.

Generator Run Times

  • Propane generators may have a limited run time based on the size of the propane tank. A 500-gallon tank can power a generator for 1 to 2 weeks depending on the load.
  • Natural gas generators can run indefinitely as long as there is a supply from the gas lines.

Considerations for Choosing

  • Location: For homes already connected to a natural gas line, natural gas generators might be more convenient and cost-effective.
  • Energy Needs and Efficiency: Propane generators may be more suitable for high energy efficiency and in areas without natural gas service.
  • Environmental Concerns: Propane is a cleaner option with a lower environmental impact.
  • Storage and Safety: Propane requires safe storage of tanks, while natural gas needs well-maintained pipelines.


Both propane and natural gas have their advantages and disadvantages. The choice depends on individual needs, cost considerations, efficiency requirements, environmental impact, safety, and availability in your area.