The cost to fill a propane tank depends on the tank size and local propane prices, which fluctuate. Here are typical costs based on tank sizes and common rates:

• Small portable tanks (e.g., 20 lb gas grill tank) typically cost around $15 to $20 to fill. For example, a 20 lb tank refill can be about $15.25 at one supplier, or about $17 at $3.79 per gallon (a 20 lb tank holds about 4.5 gallons)

• Medium tanks like 30 lb or 40 lb bottles cost roughly $22.75 to $30.50 to fill

• Larger portable tanks, such as 100 lb tanks, cost about $70 to $73 to fill

• Fixed residential tanks are usually charged by the gallon, with prices around $2.95 to $4 per gallon. For example, filling a 500-gallon tank can cost about $1,000, while a 420 lb (about 100 gallon) tank fill averages around $200

• Propane refill prices per gallon typically range from $3.00 to $4.00, with exchanges often costing more

In summary, expect to pay roughly:

• $11 minimum for very small tanks (5-10 lb)
• $15-$20 for a 20 lb tank fill
• $30-$45 for 40-60 lb tanks
• $70+ for 100 lb tanks
• Several hundred to over $1,000 for large residential tanks depending on capacity

Prices vary by location and supplier, so checking local rates is advised. Filling is generally cheaper than exchanging tanks at retail outlets