Composition and energy density
- Natural gas: primarily methane (CH4), ~1,030 BTU per cubic foot
- Propane: C3H8, ~2,516 BTU per cubic foot vapor (or 91,500 BTU per liquid gallon)
Per cubic foot, propane delivers about 2.4× the energy of natural gas. This means propane piping can be smaller diameter for the same appliance load — and that natural-gas appliances need different orifice sizes to use propane (and vice versa).
Cost comparison
Typical US 2026 retail costs:
- Natural gas at $1.20/therm: ~$12 per million BTU
- Propane at $2.80/gallon: ~$31 per million BTU
Natural gas wins decisively on cost per BTU when available. The catch is availability — natural gas distribution covers ~75% of US homes but leaves rural America without service.
Availability
- Natural gas: only inside utility distribution territory. About 75% of US homes have access; most rural and exurban areas do not.
- Propane: anywhere a delivery truck can reach. Universal US availability with an onsite tank.
Equipment compatibility
Most gas appliances can be converted between natural gas and propane with a manufacturer conversion kit — different orifice sizes and regulator settings. Kits typically cost $20–$100; installation by a licensed technician adds $100–$200. DIY conversion is illegal and dangerous.
Operational differences
- Storage: natural gas = none (continuous from utility); propane = onsite tank
- Resilience: propane = inventory on site, works without grid; natural gas = continuous but pipeline-dependent
- Pressure: appliance operating pressure ~7 in WC for NG, ~11 in WC for propane
- Regulation: NG is utility-regulated tariff; propane is dealer-set free market
When propane wins
- Natural gas not available at your address
- Off-grid or grid-unreliable area where standby generator matters
- Manufactured home with factory propane configuration
- Properties at end of long utility line where NG service is unreliable
When natural gas wins
- NG distribution covers your address (~75% of US homes)
- Cost is the dominant decision criterion
- Continuous supply without storage concerns
- Utility regulation provides price stability
FAQ
Can I convert my natural gas appliances to propane?
Yes, with the manufacturer's conversion kit installed by a licensed technician. Most appliance manufacturers (Carrier, Trane, Rheem, GE, Whirlpool etc.) sell conversion kits for $20–$100. Installation adds $100–$200. Always use the manufacturer kit — generic conversions are unsafe.
Is it worth switching from propane to natural gas if NG comes to my street?
Usually yes if you'll stay in the home long enough. Conversion costs ($1,500–$5,000 for whole-home appliance conversion) are recovered in 3–7 years through cheaper fuel. Get a written estimate from the utility before committing.