Natural gas and propane are both used for home heating, water heating, and cooking. Natural gas is delivered through underground pipelines; propane is delivered in tanks by truck. The per-BTU cost of natural gas runs roughly half the cost of propane at current US average rates. Propane delivers 2.5x the BTU per cubic foot, which means smaller tanks deliver more energy but at higher per-BTU cost. Here is the full comparison plus the conversion math for rural-to-natural-gas switching.
Per-BTU cost comparison at current US average rates
Natural gas: $1.20 per therm at retail, or about $0.012 per kBTU. Propane: $2.40 per gallon-equivalent therm, or about $0.024 per kBTU. Heating oil: $3.20 per gallon, or about $0.022 per kBTU.
Per-BTU delivered, natural gas wins by 45 to 55 percent on cost. The reason: natural gas is delivered via pipeline (low ongoing cost) while propane requires truck delivery (higher ongoing logistics cost). Heating oil similar logistics.
Safety and storage differences
Propane is heavier than air. Leaks accumulate at floor level. Carbon monoxide and explosion risks are similar to natural gas but the leak detection pattern is different (lower in the room).
Natural gas is lighter than air. Leaks rise to ceilings. Detection should be focused on basement ceilings and behind cabinets near appliances. Both fuels are odorized with mercaptan.
When propane-to-natural-gas conversion makes sense
Conversion typically costs $2,500 to $8,000 (running pipe to the home, installing meter, converting appliances). Annual operating savings: 45 to 55 percent on heating fuel.
Break-even runs 4 to 7 years on the typical conversion. For households burning more than 600 therms a year, conversion is almost always positive ROI. For households burning less, the math depends on local conversion cost.
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